Author: The Khronos® Vulkan Working Group

# Vulkan® 1.3.227 - A Specification (with all registered extensions)

The Khronos® Vulkan Working Group
version 1.3.227, 2022-09-08 16:48:57Z
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## 27. Rasterization

Rasterization is the process by which a primitive is converted to a two-dimensional image. Each discrete location of this image contains associated data such as depth, color, or other attributes.

Rasterizing a primitive begins by determining which squares of an integer grid in framebuffer coordinates are occupied by the primitive, and assigning one or more depth values to each such square. This process is described below for points, lines, and polygons.

A grid square, including its (x,y) framebuffer coordinates, z (depth), and associated data added by fragment shaders, is called a fragment. A fragment is located by its upper left corner, which lies on integer grid coordinates.

Rasterization operations also refer to a fragment’s sample locations, which are offset by fractional values from its upper left corner. The rasterization rules for points, lines, and triangles involve testing whether each sample location is inside the primitive. Fragments need not actually be square, and rasterization rules are not affected by the aspect ratio of fragments. Display of non-square grids, however, will cause rasterized points and line segments to appear fatter in one direction than the other.

We assume that fragments are square, since it simplifies antialiasing and texturing. After rasterization, fragments are processed by fragment operations.

Several factors affect rasterization, including the members of VkPipelineRasterizationStateCreateInfo and VkPipelineMultisampleStateCreateInfo.

The `VkPipelineRasterizationStateCreateInfo` structure is defined as:

    // Provided by VK_VERSION_1_0
    typedef struct VkPipelineRasterizationStateCreateInfo {
        VkStructureType                            sType;
        const void*                                pNext;
        VkPipelineRasterizationStateCreateFlags    flags;
        VkBool32                                   depthClampEnable;
        VkBool32                                   rasterizerDiscardEnable;
        VkPolygonMode                              polygonMode;
        VkCullModeFlags                            cullMode;
        VkFrontFace                                frontFace;
        VkBool32                                   depthBiasEnable;
        float                                      depthBiasConstantFactor;
        float                                      depthBiasClamp;
        float                                      depthBiasSlopeFactor;
        float                                      lineWidth;
    } VkPipelineRasterizationStateCreateInfo;

- `sType` is the type of this structure.

- `pNext` is `NULL` or a pointer to a structure extending this structure.

- `flags` is reserved for future use.

- `depthClampEnable` controls whether to clamp the fragment’s depth values as described in Depth Test. If the pipeline is not created with VkPipelineRasterizationDepthClipStateCreateInfoEXT present then enabling depth clamp will also disable clipping primitives to the z planes of the frustrum as described in Primitive Clipping. Otherwise depth clipping is controlled by the state set in VkPipelineRasterizationDepthClipStateCreateInfoEXT.

- `rasterizerDiscardEnable` controls whether primitives are discarded immediately before the rasterization stage.

- `polygonMode` is the triangle rendering mode. See VkPolygonMode.

- `cullMode` is the triangle facing direction used for primitive culling. See VkCullModeFlagBits.

- `frontFace` is a VkFrontFace value specifying the front-facing triangle orientation to be used for culling.

- `depthBiasEnable` controls whether to bias fragment depth values.

- `depthBiasConstantFactor` is a scalar factor controlling the constant depth value added to each fragment.

- `depthBiasClamp` is the maximum (or minimum) depth bias of a fragment.

- `depthBiasSlopeFactor` is a scalar factor applied to a fragment’s slope in depth bias calculations.

- `lineWidth` is the width of rasterized line segments.

The application can also add a `VkPipelineRasterizationStateRasterizationOrderAMD` structure to the `pNext` chain of a VkPipelineRasterizationStateCreateInfo structure. This structure enables selecting the rasterization order to use when rendering with the corresponding graphics pipeline as described in Rasterization Order.

Valid Usage

- VUID-VkPipelineRasterizationStateCreateInfo-depthClampEnable-00782
  If the `depthClamp` feature is not enabled, `depthClampEnable` must be `VK_FALSE`

- VUID-VkPipelineRasterizationStateCreateInfo-polygonMode-01507
  If the `fillModeNonSolid` feature is not enabled, `polygonMode` must be `VK_POLYGON_MODE_FILL` or `VK_POLYGON_MODE_FILL_RECTANGLE_NV`

- VUID-VkPipelineRasterizationStateCreateInfo-polygonMode-01414
  If the `VK_NV_fill_rectangle` extension is not enabled, `polygonMode` must not be `VK_POLYGON_MODE_FILL_RECTANGLE_NV`

- VUID-VkPipelineRasterizationStateCreateInfo-pointPolygons-04458
  If the `VK_KHR_portability_subset` extension is enabled, and VkPhysicalDevicePortabilitySubsetFeaturesKHR::`pointPolygons` is `VK_FALSE`, and `rasterizerDiscardEnable` is `VK_FALSE`, `polygonMode` must not be `VK_POLYGON_MODE_POINT`

Valid Usage (Implicit)

- VUID-VkPipelineRasterizationStateCreateInfo-sType-sType
  `sType` must be `VK_STRUCTURE_TYPE_PIPELINE_RASTERIZATION_STATE_CREATE_INFO`

- VUID-VkPipelineRasterizationStateCreateInfo-pNext-pNext
  Each `pNext` member of any structure (including this one) in the `pNext` chain must be either `NULL` or a pointer to a valid instance of VkPipelineRasterizationConservativeStateCreateInfoEXT, VkPipelineRasterizationDepthClipStateCreateInfoEXT, VkPipelineRasterizationLineStateCreateInfoEXT, VkPipelineRasterizationProvokingVertexStateCreateInfoEXT, VkPipelineRasterizationStateRasterizationOrderAMD, or VkPipelineRasterizationStateStreamCreateInfoEXT

- VUID-VkPipelineRasterizationStateCreateInfo-sType-unique
  The `sType` value of each struct in the `pNext` chain must be unique

- VUID-VkPipelineRasterizationStateCreateInfo-flags-zerobitmask
  `flags` must be `0`

- VUID-VkPipelineRasterizationStateCreateInfo-polygonMode-parameter
  `polygonMode` must be a valid VkPolygonMode value

- VUID-VkPipelineRasterizationStateCreateInfo-cullMode-parameter
  `cullMode` must be a valid combination of VkCullModeFlagBits values

- VUID-VkPipelineRasterizationStateCreateInfo-frontFace-parameter
  `frontFace` must be a valid VkFrontFace value

    // Provided by VK_VERSION_1_0
    typedef VkFlags VkPipelineRasterizationStateCreateFlags;

`VkPipelineRasterizationStateCreateFlags` is a bitmask type for setting a mask, but is currently reserved for future use.

If the `pNext` chain of VkPipelineRasterizationStateCreateInfo includes a `VkPipelineRasterizationDepthClipStateCreateInfoEXT` structure, then that structure controls whether depth clipping is enabled or disabled.

The `VkPipelineRasterizationDepthClipStateCreateInfoEXT` structure is defined as:

    // Provided by VK_EXT_depth_clip_enable
    typedef struct VkPipelineRasterizationDepthClipStateCreateInfoEXT {
        VkStructureType                                        sType;
        const void*                                            pNext;
        VkPipelineRasterizationDepthClipStateCreateFlagsEXT    flags;
        VkBool32                                               depthClipEnable;
    } VkPipelineRasterizationDepthClipStateCreateInfoEXT;

- `sType` is the type of this structure.

- `pNext` is `NULL` or a pointer to a structure extending this structure.

- `flags` is reserved for future use.

- `depthClipEnable` controls whether depth clipping is enabled as described in Primitive Clipping.

Valid Usage (Implicit)

- VUID-VkPipelineRasterizationDepthClipStateCreateInfoEXT-sType-sType
  `sType` must be `VK_STRUCTURE_TYPE_PIPELINE_RASTERIZATION_DEPTH_CLIP_STATE_CREATE_INFO_EXT`

- VUID-VkPipelineRasterizationDepthClipStateCreateInfoEXT-flags-zerobitmask
  `flags` must be `0`

    // Provided by VK_EXT_depth_clip_enable
    typedef VkFlags VkPipelineRasterizationDepthClipStateCreateFlagsEXT;

`VkPipelineRasterizationDepthClipStateCreateFlagsEXT` is a bitmask type for setting a mask, but is currently reserved for future use.

The `VkPipelineMultisampleStateCreateInfo` structure is defined as:

    // Provided by VK_VERSION_1_0
    typedef struct VkPipelineMultisampleStateCreateInfo {
        VkStructureType                          sType;
        const void*                              pNext;
        VkPipelineMultisampleStateCreateFlags    flags;
        VkSampleCountFlagBits                    rasterizationSamples;
        VkBool32                                 sampleShadingEnable;
        float                                    minSampleShading;
        const VkSampleMask*                      pSampleMask;
        VkBool32                                 alphaToCoverageEnable;
        VkBool32                                 alphaToOneEnable;
    } VkPipelineMultisampleStateCreateInfo;

- `sType` is the type of this structure.

- `pNext` is `NULL` or a pointer to a structure extending this structure.

- `flags` is reserved for future use.

- `rasterizationSamples` is a VkSampleCountFlagBits value specifying the number of samples used in rasterization.

- `sampleShadingEnable` can be used to enable Sample Shading.

- `minSampleShading` specifies a minimum fraction of sample shading if `sampleShadingEnable` is set to `VK_TRUE`.

- `pSampleMask` is a pointer to an array of `VkSampleMask` values used in the sample mask test.

- `alphaToCoverageEnable` controls whether a temporary coverage value is generated based on the alpha component of the fragment’s first color output as specified in the Multisample Coverage section.

- `alphaToOneEnable` controls whether the alpha component of the fragment’s first color output is replaced with one as described in Multisample Coverage.

Each bit in the sample mask is associated with a unique sample index as defined for the coverage mask. Each bit b for mask word w in the sample mask corresponds to sample index i, where i = 32 × w + b. `pSampleMask` has a length equal to ⌈ `rasterizationSamples` / 32 ⌉ words.

If `pSampleMask` is `NULL`, it is treated as if the mask has all bits set to `1`.

Valid Usage

- VUID-VkPipelineMultisampleStateCreateInfo-sampleShadingEnable-00784
  If the `sampleRateShading` feature is not enabled, `sampleShadingEnable` must be `VK_FALSE`

- VUID-VkPipelineMultisampleStateCreateInfo-alphaToOneEnable-00785
  If the `alphaToOne` feature is not enabled, `alphaToOneEnable` must be `VK_FALSE`

- VUID-VkPipelineMultisampleStateCreateInfo-minSampleShading-00786
  `minSampleShading` must be in the range [0,1]

- VUID-VkPipelineMultisampleStateCreateInfo-rasterizationSamples-01415
  If the `VK_NV_framebuffer_mixed_samples` extension is enabled, and if the subpass has any color attachments and `rasterizationSamples` is greater than the number of color samples, then `sampleShadingEnable` must be `VK_FALSE`

Valid Usage (Implicit)

- VUID-VkPipelineMultisampleStateCreateInfo-sType-sType
  `sType` must be `VK_STRUCTURE_TYPE_PIPELINE_MULTISAMPLE_STATE_CREATE_INFO`

- VUID-VkPipelineMultisampleStateCreateInfo-pNext-pNext
  Each `pNext` member of any structure (including this one) in the `pNext` chain must be either `NULL` or a pointer to a valid instance of VkPipelineCoverageModulationStateCreateInfoNV, VkPipelineCoverageReductionStateCreateInfoNV, VkPipelineCoverageToColorStateCreateInfoNV, or VkPipelineSampleLocationsStateCreateInfoEXT

- VUID-VkPipelineMultisampleStateCreateInfo-sType-unique
  The `sType` value of each struct in the `pNext` chain must be unique

- VUID-VkPipelineMultisampleStateCreateInfo-flags-zerobitmask
  `flags` must be `0`

- VUID-VkPipelineMultisampleStateCreateInfo-rasterizationSamples-parameter
  `rasterizationSamples` must be a valid VkSampleCountFlagBits value

- VUID-VkPipelineMultisampleStateCreateInfo-pSampleMask-parameter
  If `pSampleMask` is not `NULL`, `pSampleMask` must be a valid pointer to an array of ⌈32 rasterizationSamples​⌉ `VkSampleMask` values

    // Provided by VK_VERSION_1_0
    typedef VkFlags VkPipelineMultisampleStateCreateFlags;

`VkPipelineMultisampleStateCreateFlags` is a bitmask type for setting a mask, but is currently reserved for future use.

The elements of the sample mask array are of type `VkSampleMask`, each representing 32 bits of coverage information:

    // Provided by VK_VERSION_1_0
    typedef uint32_t VkSampleMask;

Rasterization only generates fragments which cover one or more pixels inside the framebuffer. Pixels outside the framebuffer are never considered covered in the fragment. Fragments which would be produced by application of any of the primitive rasterization rules described below but which lie outside the framebuffer are not produced, nor are they processed by any later stage of the pipeline, including any of the fragment operations.

Surviving fragments are processed by fragment shaders. Fragment shaders determine associated data for fragments, and can also modify or replace their assigned depth values.

### 27.1. Discarding Primitives Before Rasterization

Primitives are discarded before rasterization if the `rasterizerDiscardEnable` member of VkPipelineRasterizationStateCreateInfo is enabled. When enabled, primitives are discarded after they are processed by the last active shader stage in the pipeline before rasterization.

To dynamically enable whether primitives are discarded before the rasterization stage, call:

    // Provided by VK_VERSION_1_3
    void vkCmdSetRasterizerDiscardEnable(
        VkCommandBuffer                             commandBuffer,
        VkBool32                                    rasterizerDiscardEnable);

or the equivalent command

    // Provided by VK_EXT_extended_dynamic_state2
    void vkCmdSetRasterizerDiscardEnableEXT(
        VkCommandBuffer                             commandBuffer,
        VkBool32                                    rasterizerDiscardEnable);

- `commandBuffer` is the command buffer into which the command will be recorded.

- `rasterizerDiscardEnable` controls whether primitives are discarded immediately before the rasterization stage.

This command sets the discard enable for subsequent drawing commands when the graphics pipeline is created with `VK_DYNAMIC_STATE_RASTERIZER_DISCARD_ENABLE` set in VkPipelineDynamicStateCreateInfo::`pDynamicStates`. Otherwise, this state is specified by the VkPipelineRasterizationStateCreateInfo::`rasterizerDiscardEnable` value used to create the currently active pipeline.

Valid Usage (Implicit)

- VUID-vkCmdSetRasterizerDiscardEnable-commandBuffer-parameter
  `commandBuffer` must be a valid VkCommandBuffer handle

- VUID-vkCmdSetRasterizerDiscardEnable-commandBuffer-recording
  `commandBuffer` must be in the recording state

- VUID-vkCmdSetRasterizerDiscardEnable-commandBuffer-cmdpool
  The `VkCommandPool` that `commandBuffer` was allocated from must support graphics operations

- VUID-vkCmdSetRasterizerDiscardEnable-videocoding
  This command must only be called outside of a video coding scope

Host Synchronization

- Host access to `commandBuffer` must be externally synchronized

- Host access to the `VkCommandPool` that `commandBuffer` was allocated from must be externally synchronized

Command Properties

Command Buffer Levels | Render Pass Scope | Video Coding Scope | Supported Queue Types
--- | --- | --- | ---
Primary Secondary | Both | Outside | Graphics

### 27.2. Controlling the Vertex Stream Used for Rasterization

By default vertex data output from the last pre-rasterization shader stage are directed to vertex stream zero. Geometry shaders can emit primitives to multiple independent vertex streams. Each vertex emitted by the geometry shader is directed at one of the vertex streams. As vertices are received on each vertex stream, they are arranged into primitives of the type specified by the geometry shader output primitive type. The shading language instructions `OpEndPrimitive` and `OpEndStreamPrimitive` can be used to end the primitive being assembled on a given vertex stream and start a new empty primitive of the same type. An implementation supports up to `VkPhysicalDeviceTransformFeedbackPropertiesEXT`::`maxTransformFeedbackStreams` streams, which is at least 1. The individual streams are numbered 0 through `maxTransformFeedbackStreams` minus 1. There is no requirement on the order of the streams to which vertices are emitted, and the number of vertices emitted to each vertex stream can be completely independent, subject only to the `VkPhysicalDeviceTransformFeedbackPropertiesEXT`::`maxTransformFeedbackStreamDataSize` and `VkPhysicalDeviceTransformFeedbackPropertiesEXT`::`maxTransformFeedbackBufferDataSize` limits. The primitives output from all vertex streams are passed to the transform feedback stage to be captured to transform feedback buffers in the manner specified by the last pre-rasterization shader stage shader’s `XfbBuffer`, `XfbStride`, and `Offsets` decorations on the output interface variables in the graphics pipeline. To use a vertex stream other than zero, or to use multiple streams, the `GeometryStreams` capability must be specified.

By default, the primitives output from vertex stream zero are rasterized. If the implementation supports the VkPhysicalDeviceTransformFeedbackPropertiesEXT::`transformFeedbackRasterizationStreamSelect` property it is possible to rasterize a vertex stream other than zero.

By default, geometry shaders that emit vertices to multiple vertex streams are limited to using only the `OutputPoints` output primitive type. If the implementation supports the VkPhysicalDeviceTransformFeedbackPropertiesEXT::`transformFeedbackStreamsLinesTriangles` property it is possible to emit `OutputLineStrip` or `OutputTriangleStrip` in addition to `OutputPoints`.

The vertex stream used for rasterization is specified by adding a `VkPipelineRasterizationStateStreamCreateInfoEXT` structure to the `pNext` chain of a VkPipelineRasterizationStateCreateInfo structure.

The `VkPipelineRasterizationStateStreamCreateInfoEXT` structure is defined as:

    // Provided by VK_EXT_transform_feedback
    typedef struct VkPipelineRasterizationStateStreamCreateInfoEXT {
        VkStructureType                                     sType;
        const void*                                         pNext;
        VkPipelineRasterizationStateStreamCreateFlagsEXT    flags;
        uint32_t                                            rasterizationStream;
    } VkPipelineRasterizationStateStreamCreateInfoEXT;

- `sType` is the type of this structure.

- `pNext` is `NULL` or a pointer to a structure extending this structure.

- `flags` is reserved for future use.

- `rasterizationStream` is the vertex stream selected for rasterization.

If this structure is not present, `rasterizationStream` is assumed to be zero.

Valid Usage

- VUID-VkPipelineRasterizationStateStreamCreateInfoEXT-geometryStreams-02324
  `VkPhysicalDeviceTransformFeedbackFeaturesEXT`::`geometryStreams` must be enabled

- VUID-VkPipelineRasterizationStateStreamCreateInfoEXT-rasterizationStream-02325
  `rasterizationStream` must be less than VkPhysicalDeviceTransformFeedbackPropertiesEXT::`maxTransformFeedbackStreams`

- VUID-VkPipelineRasterizationStateStreamCreateInfoEXT-rasterizationStream-02326
  `rasterizationStream` must be zero if `VkPhysicalDeviceTransformFeedbackPropertiesEXT`::`transformFeedbackRasterizationStreamSelect` is `VK_FALSE`

Valid Usage (Implicit)

- VUID-VkPipelineRasterizationStateStreamCreateInfoEXT-sType-sType
  `sType` must be `VK_STRUCTURE_TYPE_PIPELINE_RASTERIZATION_STATE_STREAM_CREATE_INFO_EXT`

- VUID-VkPipelineRasterizationStateStreamCreateInfoEXT-flags-zerobitmask
  `flags` must be `0`

    // Provided by VK_EXT_transform_feedback
    typedef VkFlags VkPipelineRasterizationStateStreamCreateFlagsEXT;

`VkPipelineRasterizationStateStreamCreateFlagsEXT` is a bitmask type for setting a mask, but is currently reserved for future use.

### 27.3. Rasterization Order

Within a subpass of a render pass instance, for a given (x,y,layer,sample) sample location, the following operations are guaranteed to execute in rasterization order, for each separate primitive that includes that sample location:

1. Fragment operations, in the order defined

2. Blending, logic operations, and color writes

Execution of these operations for each primitive in a subpass occurs in an order determined by the application.

The rasterization order to use for a graphics pipeline is specified by adding a `VkPipelineRasterizationStateRasterizationOrderAMD` structure to the `pNext` chain of a VkPipelineRasterizationStateCreateInfo structure.

The `VkPipelineRasterizationStateRasterizationOrderAMD` structure is defined as:

    // Provided by VK_AMD_rasterization_order
    typedef struct VkPipelineRasterizationStateRasterizationOrderAMD {
        VkStructureType            sType;
        const void*                pNext;
        VkRasterizationOrderAMD    rasterizationOrder;
    } VkPipelineRasterizationStateRasterizationOrderAMD;

- `sType` is the type of this structure.

- `pNext` is `NULL` or a pointer to a structure extending this structure.

- `rasterizationOrder` is a VkRasterizationOrderAMD value specifying the primitive rasterization order to use.

Valid Usage (Implicit)

- VUID-VkPipelineRasterizationStateRasterizationOrderAMD-sType-sType
  `sType` must be `VK_STRUCTURE_TYPE_PIPELINE_RASTERIZATION_STATE_RASTERIZATION_ORDER_AMD`

- VUID-VkPipelineRasterizationStateRasterizationOrderAMD-rasterizationOrder-parameter
  `rasterizationOrder` must be a valid VkRasterizationOrderAMD value

If the `VK_AMD_rasterization_order` device extension is not enabled or the application does not request a particular rasterization order through specifying a `VkPipelineRasterizationStateRasterizationOrderAMD` structure then the rasterization order used by the graphics pipeline defaults to `VK_RASTERIZATION_ORDER_STRICT_AMD`.

Possible values of VkPipelineRasterizationStateRasterizationOrderAMD::`rasterizationOrder`, specifying the primitive rasterization order, are:

    // Provided by VK_AMD_rasterization_order
    typedef enum VkRasterizationOrderAMD {
        VK_RASTERIZATION_ORDER_STRICT_AMD = 0,
        VK_RASTERIZATION_ORDER_RELAXED_AMD = 1,
    } VkRasterizationOrderAMD;

- `VK_RASTERIZATION_ORDER_STRICT_AMD` specifies that operations for each primitive in a subpass must occur in primitive order.

- `VK_RASTERIZATION_ORDER_RELAXED_AMD` specifies that operations for each primitive in a subpass may not occur in primitive order.

### 27.4. Multisampling

Multisampling is a mechanism to antialias all Vulkan primitives: points, lines, and polygons. The technique is to sample all primitives multiple times at each pixel. Each sample in each framebuffer attachment has storage for a color, depth, and/or stencil value, such that per-fragment operations apply to each sample independently. The color sample values can be later resolved to a single color (see Resolving Multisample Images and the Render Pass chapter for more details on how to resolve multisample images to non-multisample images).

Vulkan defines rasterization rules for single-sample modes in a way that is equivalent to a multisample mode with a single sample in the center of each fragment.

Each fragment includes a coverage mask with a single bit for each sample in the fragment, and a number of depth values and associated data for each sample.

It is understood that each pixel has `rasterizationSamples` locations associated with it. These locations are exact positions, rather than regions or areas, and each is referred to as a sample point. The sample points associated with a pixel must be located inside or on the boundary of the unit square that is considered to bound the pixel. Furthermore, the relative locations of sample points may be identical for each pixel in the framebuffer, or they may differ.

If the render pass has a fragment density map attachment, each fragment only has `rasterizationSamples` locations associated with it regardless of how many pixels are covered in the fragment area. Fragment sample locations are defined as if the fragment had an area of (1,1) and its sample points must be located within these bounds. Their actual location in the framebuffer is calculated by scaling the sample location by the fragment area. Attachments with storage for multiple samples per pixel are located at the pixel sample locations. Otherwise, the fragment’s sample locations are generally used for evaluation of associated data and fragment operations.

If the current pipeline includes a fragment shader with one or more variables in its interface decorated with `Sample` and `Input`, the data associated with those variables will be assigned independently for each sample. The values for each sample must be evaluated at the location of the sample. The data associated with any other variables not decorated with `Sample` and `Input` need not be evaluated independently for each sample.

A coverage mask is generated for each fragment, based on which samples within that fragment are determined to be within the area of the primitive that generated the fragment.

Single pixel fragments and multi-pixel fragments defined by a fragment density map have one set of samples. Multi-pixel fragments defined by a shading rate image have one set of samples per pixel. Multi-pixel fragments defined by setting the fragment shading rate have one set of samples per pixel. Each set of samples has a number of samples determined by VkPipelineMultisampleStateCreateInfo::`rasterizationSamples`. Each sample in a set is assigned a unique sample index i in the range [0, `rasterizationSamples`).

Each sample in a fragment is also assigned a unique coverage index j in the range [0, n × `rasterizationSamples`), where n is the number of sets in the fragment. If the fragment contains a single set of samples, the coverage index is always equal to the sample index. If a shading rate image is used and a fragment covers multiple pixels, the coverage index is determined as defined by VkPipelineViewportCoarseSampleOrderStateCreateInfoNV or vkCmdSetCoarseSampleOrderNV.

If the fragment shading rate is set, the coverage index j is determined as a function of the pixel index p, the sample index i, and the number of rasterization samples r as:

  j = i + r × ((fw × fh) - 1 - p)

where the pixel index p is determined as a function of the pixel’s framebuffer location (x,y) and the fragment size (fw,fh):

  px = x % fw

  py = y % fh

  p = px + (py × fw)

The table below illustrates the pixel index for multi-pixel fragments:

Table 33. Pixel indices - 1 wide
1x1 | 1x2 | 1x4
--- | --- | ---

Table 34. Pixel indices - 2 wide
2x1 | 2x2 | 2x4
--- | --- | ---

Table 35. Pixel indices - 4 wide
4x1 | 4x2 | 4x4
--- | --- | ---

The coverage mask includes B bits packed into W words, defined as:

  B = n × `rasterizationSamples`

  W = ⌈B/32⌉

Bit b in coverage mask word w is `1` if the sample with coverage index j = 32×w + b is covered, and `0` otherwise.

If the `standardSampleLocations` member of VkPhysicalDeviceLimits is `VK_TRUE`, then the sample counts `VK_SAMPLE_COUNT_1_BIT`, `VK_SAMPLE_COUNT_2_BIT`, `VK_SAMPLE_COUNT_4_BIT`, `VK_SAMPLE_COUNT_8_BIT`, and `VK_SAMPLE_COUNT_16_BIT` have sample locations as listed in the following table, with the ith entry in the table corresponding to sample index i. `VK_SAMPLE_COUNT_32_BIT` and `VK_SAMPLE_COUNT_64_BIT` do not have standard sample locations. Locations are defined relative to an origin in the upper left corner of the fragment.

Table 36. Standard sample locations
Sample count | Sample Locations
--- | ---
`VK_SAMPLE_COUNT_1_BIT` | (0.5,0.5) |
`VK_SAMPLE_COUNT_2_BIT` | (0.75,0.75) (0.25,0.25) |
`VK_SAMPLE_COUNT_4_BIT` | (0.375, 0.125) (0.875, 0.375) (0.125, 0.625) (0.625, 0.875) |
`VK_SAMPLE_COUNT_8_BIT` | (0.5625, 0.3125) (0.4375, 0.6875) (0.8125, 0.5625) (0.3125, 0.1875) (0.1875, 0.8125) (0.0625, 0.4375) (0.6875, 0.9375) (0.9375, 0.0625) |
`VK_SAMPLE_COUNT_16_BIT` | (0.5625, 0.5625) (0.4375, 0.3125) (0.3125, 0.625) (0.75, 0.4375) (0.1875, 0.375) (0.625, 0.8125) (0.8125, 0.6875) (0.6875, 0.1875) (0.375, 0.875) (0.5, 0.0625) (0.25, 0.125) (0.125, 0.75) (0.0, 0.5) (0.9375, 0.25) (0.875, 0.9375) (0.0625, 0.0) |

Color images created with multiple samples per pixel use a compression technique where there are two arrays of data associated with each pixel. The first array contains one element per sample where each element stores an index to the second array defining the fragment mask of the pixel. The second array contains one element per color fragment and each element stores a unique color value in the format of the image. With this compression technique it is not always necessary to actually use unique storage locations for each color sample: when multiple samples share the same color value the fragment mask may have two samples referring to the same color fragment. The number of color fragments is determined by the `samples` member of the VkImageCreateInfo structure used to create the image. The `VK_AMD_shader_fragment_mask` device extension provides shader instructions enabling the application to get direct access to the fragment mask and the individual color fragment values.

Figure 19. Fragment Mask

### 27.5. Custom Sample Locations

Applications can also control the sample locations used for rasterization.

If the `pNext` chain of the VkPipelineMultisampleStateCreateInfo structure specified at pipeline creation time includes a `VkPipelineSampleLocationsStateCreateInfoEXT` structure, then that structure controls the sample locations used when rasterizing primitives with the pipeline.

The `VkPipelineSampleLocationsStateCreateInfoEXT` structure is defined as:

    // Provided by VK_EXT_sample_locations
    typedef struct VkPipelineSampleLocationsStateCreateInfoEXT {
        VkStructureType             sType;
        const void*                 pNext;
        VkBool32                    sampleLocationsEnable;
        VkSampleLocationsInfoEXT    sampleLocationsInfo;
    } VkPipelineSampleLocationsStateCreateInfoEXT;

- `sType` is the type of this structure.

- `pNext` is `NULL` or a pointer to a structure extending this structure.

- `sampleLocationsEnable` controls whether custom sample locations are used. If `sampleLocationsEnable` is `VK_FALSE`, the default sample locations are used and the values specified in `sampleLocationsInfo` are ignored.

- `sampleLocationsInfo` is the sample locations to use during rasterization if `sampleLocationsEnable` is `VK_TRUE` and the graphics pipeline is not created with `VK_DYNAMIC_STATE_SAMPLE_LOCATIONS_EXT`.

Valid Usage (Implicit)

- VUID-VkPipelineSampleLocationsStateCreateInfoEXT-sType-sType
  `sType` must be `VK_STRUCTURE_TYPE_PIPELINE_SAMPLE_LOCATIONS_STATE_CREATE_INFO_EXT`

- VUID-VkPipelineSampleLocationsStateCreateInfoEXT-sampleLocationsInfo-parameter
  `sampleLocationsInfo` must be a valid VkSampleLocationsInfoEXT structure

The `VkSampleLocationsInfoEXT` structure is defined as:

    // Provided by VK_EXT_sample_locations
    typedef struct VkSampleLocationsInfoEXT {
        VkStructureType               sType;
        const void*                   pNext;
        VkSampleCountFlagBits         sampleLocationsPerPixel;
        VkExtent2D                    sampleLocationGridSize;
        uint32_t                      sampleLocationsCount;
        const VkSampleLocationEXT*    pSampleLocations;
    } VkSampleLocationsInfoEXT;

- `sType` is the type of this structure.

- `pNext` is `NULL` or a pointer to a structure extending this structure.

- `sampleLocationsPerPixel` is a VkSampleCountFlagBits value specifying the number of sample locations per pixel.

- `sampleLocationGridSize` is the size of the sample location grid to select custom sample locations for.

- `sampleLocationsCount` is the number of sample locations in `pSampleLocations`.

- `pSampleLocations` is a pointer to an array of `sampleLocationsCount` VkSampleLocationEXT structures.

This structure can be used either to specify the sample locations to be used for rendering or to specify the set of sample locations an image subresource has been last rendered with for the purposes of layout transitions of depth/stencil images created with `VK_IMAGE_CREATE_SAMPLE_LOCATIONS_COMPATIBLE_DEPTH_BIT_EXT`.

The sample locations in `pSampleLocations` specify `sampleLocationsPerPixel` number of sample locations for each pixel in the grid of the size specified in `sampleLocationGridSize`. The sample location for sample i at the pixel grid location (x,y) is taken from `pSampleLocations`[(x + y × `sampleLocationGridSize.width`) × `sampleLocationsPerPixel` + i].

If the render pass has a fragment density map, the implementation will choose the sample locations for the fragment and the contents of `pSampleLocations` may be ignored.

Valid Usage

- VUID-VkSampleLocationsInfoEXT-sampleLocationsPerPixel-01526
  `sampleLocationsPerPixel` must be a bit value that is set in VkPhysicalDeviceSampleLocationsPropertiesEXT::`sampleLocationSampleCounts`

- VUID-VkSampleLocationsInfoEXT-sampleLocationsCount-01527
  `sampleLocationsCount` must equal `sampleLocationsPerPixel` × `sampleLocationGridSize.width` × `sampleLocationGridSize.height`

Valid Usage (Implicit)

- VUID-VkSampleLocationsInfoEXT-sType-sType
  `sType` must be `VK_STRUCTURE_TYPE_SAMPLE_LOCATIONS_INFO_EXT`

- VUID-VkSampleLocationsInfoEXT-pSampleLocations-parameter
  If `sampleLocationsCount` is not `0`, `pSampleLocations` must be a valid pointer to an array of `sampleLocationsCount` VkSampleLocationEXT structures

The `VkSampleLocationEXT` structure is defined as:

    // Provided by VK_EXT_sample_locations
    typedef struct VkSampleLocationEXT {
        float    x;
        float    y;
    } VkSampleLocationEXT;

- `x` is the horizontal coordinate of the sample’s location.

- `y` is the vertical coordinate of the sample’s location.

The domain space of the sample location coordinates has an upper-left origin within the pixel in framebuffer space.

The values specified in a `VkSampleLocationEXT` structure are always clamped to the implementation-dependent sample location coordinate range [`sampleLocationCoordinateRange`[0],`sampleLocationCoordinateRange`[1]] that can be queried using VkPhysicalDeviceSampleLocationsPropertiesEXT.

To dynamically set the sample locations used for rasterization, call:

    // Provided by VK_EXT_sample_locations
    void vkCmdSetSampleLocationsEXT(
        VkCommandBuffer                             commandBuffer,
        const VkSampleLocationsInfoEXT*             pSampleLocationsInfo);

- `commandBuffer` is the command buffer into which the command will be recorded.

- `pSampleLocationsInfo` is the sample locations state to set.

This command sets the custom sample locations for subsequent drawing commands when the graphics pipeline is created with `VK_DYNAMIC_STATE_SAMPLE_LOCATIONS_EXT` set in VkPipelineDynamicStateCreateInfo::`pDynamicStates`, and when the VkPipelineSampleLocationsStateCreateInfoEXT::`sampleLocationsEnable` property of the bound graphics pipeline is `VK_TRUE`. Otherwise, this state is specified by the VkPipelineSampleLocationsStateCreateInfoEXT::`sampleLocationsInfo` values used to create the currently active pipeline.

Valid Usage

- VUID-vkCmdSetSampleLocationsEXT-sampleLocationsPerPixel-01529
  The `sampleLocationsPerPixel` member of `pSampleLocationsInfo` must equal the `rasterizationSamples` member of the VkPipelineMultisampleStateCreateInfo structure the bound graphics pipeline has been created with

- VUID-vkCmdSetSampleLocationsEXT-variableSampleLocations-01530
  If VkPhysicalDeviceSampleLocationsPropertiesEXT::`variableSampleLocations` is `VK_FALSE` then the current render pass must have been begun by specifying a VkRenderPassSampleLocationsBeginInfoEXT structure whose `pPostSubpassSampleLocations` member contains an element with a `subpassIndex` matching the current subpass index and the `sampleLocationsInfo` member of that element must match the sample locations state pointed to by `pSampleLocationsInfo`

Valid Usage (Implicit)

- VUID-vkCmdSetSampleLocationsEXT-commandBuffer-parameter
  `commandBuffer` must be a valid VkCommandBuffer handle

- VUID-vkCmdSetSampleLocationsEXT-pSampleLocationsInfo-parameter
  `pSampleLocationsInfo` must be a valid pointer to a valid VkSampleLocationsInfoEXT structure

- VUID-vkCmdSetSampleLocationsEXT-commandBuffer-recording
  `commandBuffer` must be in the recording state

- VUID-vkCmdSetSampleLocationsEXT-commandBuffer-cmdpool
  The `VkCommandPool` that `commandBuffer` was allocated from must support graphics operations

- VUID-vkCmdSetSampleLocationsEXT-videocoding
  This command must only be called outside of a video coding scope

Host Synchronization

- Host access to `commandBuffer` must be externally synchronized

- Host access to the `VkCommandPool` that `commandBuffer` was allocated from must be externally synchronized

Command Properties

Command Buffer Levels | Render Pass Scope | Video Coding Scope | Supported Queue Types
--- | --- | --- | ---
Primary Secondary | Both | Outside | Graphics

### 27.6. Fragment Shading Rates

The features advertised by VkPhysicalDeviceFragmentShadingRateFeaturesKHR allow an application to control the shading rate of a given fragment shader invocation.

The fragment shading rate strongly interacts with Multisampling, and the set of available rates for an implementation may be restricted by sample rate.

To query available shading rates, call:

    // Provided by VK_KHR_fragment_shading_rate
    VkResult vkGetPhysicalDeviceFragmentShadingRatesKHR(
        VkPhysicalDevice                            physicalDevice,
        uint32_t*                                   pFragmentShadingRateCount,
        VkPhysicalDeviceFragmentShadingRateKHR*     pFragmentShadingRates);

- `physicalDevice` is the handle to the physical device whose properties will be queried.

- `pFragmentShadingRateCount` is a pointer to an integer related to the number of fragment shading rates available or queried, as described below.

- `pFragmentShadingRates` is either `NULL` or a pointer to an array of VkPhysicalDeviceFragmentShadingRateKHR structures.

If `pFragmentShadingRates` is `NULL`, then the number of fragment shading rates available is returned in `pFragmentShadingRateCount`. Otherwise, `pFragmentShadingRateCount` must point to a variable set by the user to the number of elements in the `pFragmentShadingRates` array, and on return the variable is overwritten with the number of structures actually written to `pFragmentShadingRates`. If `pFragmentShadingRateCount` is less than the number of fragment shading rates available, at most `pFragmentShadingRateCount` structures will be written, and `VK_INCOMPLETE` will be returned instead of `VK_SUCCESS`, to indicate that not all the available fragment shading rates were returned.

The returned array of fragment shading rates must be ordered from largest `fragmentSize.width` value to smallest, and each set of fragment shading rates with the same `fragmentSize.width` value must be ordered from largest `fragmentSize.height` to smallest. Any two entries in the array must not have the same `fragmentSize` values.

For any entry in the array, the following rules also apply:

- The value of `fragmentSize.width` must be less than or equal to `maxFragmentSize.width`.

- The value of `fragmentSize.width` must be greater than or equal to `1`.

- The value of `fragmentSize.width` must be a power-of-two.

- The value of `fragmentSize.height` must be less than or equal to `maxFragmentSize.height`.

- The value of `fragmentSize.height` must be greater than or equal to `1`.

- The value of `fragmentSize.height` must be a power-of-two.

- The highest sample count in `sampleCounts` must be less than or equal to `maxFragmentShadingRateRasterizationSamples`.

- The product of `fragmentSize.width`, `fragmentSize.height`, and the highest sample count in `sampleCounts` must be less than or equal to `maxFragmentShadingRateCoverageSamples`.

Implementations must support at least the following shading rates:

`sampleCounts` | `fragmentSize`
--- | ---
`VK_SAMPLE_COUNT_1_BIT` | `VK_SAMPLE_COUNT_4_BIT` | {2,2}
`VK_SAMPLE_COUNT_1_BIT` | `VK_SAMPLE_COUNT_4_BIT` | {2,1}
~0 | {1,1}

If `framebufferColorSampleCounts`, includes `VK_SAMPLE_COUNT_2_BIT`, the required rates must also include `VK_SAMPLE_COUNT_2_BIT`.

| Note Including the {1,1} fragment size is done for completeness; it has no actual effect on the support of rendering without setting the fragment size. All sample counts and render pass transforms are supported for this rate.

The returned set of fragment shading rates must be returned in the native (rotated) coordinate system. For rasterization using render pass `transform` not equal to `VK_SURFACE_TRANSFORM_IDENTITY_BIT_KHR`, the application must transform the returned fragment shading rates into the current (unrotated) coordinate system to get the supported rates for that transform.

| Note For example, consider an implementation returning support for 4x2, but not 2x4 in the set of supported fragment shading rates. This means that for transforms `VK_SURFACE_TRANSFORM_ROTATE_90_BIT_KHR` and `VK_SURFACE_TRANSFORM_ROTATE_270_BIT_KHR`, 2x4 is a supported rate, but 4x2 is an unsupported rate.

Valid Usage (Implicit)

- VUID-vkGetPhysicalDeviceFragmentShadingRatesKHR-physicalDevice-parameter
  `physicalDevice` must be a valid VkPhysicalDevice handle

- VUID-vkGetPhysicalDeviceFragmentShadingRatesKHR-pFragmentShadingRateCount-parameter
  `pFragmentShadingRateCount` must be a valid pointer to a `uint32_t` value

- VUID-vkGetPhysicalDeviceFragmentShadingRatesKHR-pFragmentShadingRates-parameter
  If the value referenced by `pFragmentShadingRateCount` is not `0`, and `pFragmentShadingRates` is not `NULL`, `pFragmentShadingRates` must be a valid pointer to an array of `pFragmentShadingRateCount` VkPhysicalDeviceFragmentShadingRateKHR structures

Return Codes

Success

  - `VK_SUCCESS`

  - `VK_INCOMPLETE`

Failure

  - `VK_ERROR_OUT_OF_HOST_MEMORY`

The `VkPhysicalDeviceFragmentShadingRateKHR` structure is defined as

    // Provided by VK_KHR_fragment_shading_rate
    typedef struct VkPhysicalDeviceFragmentShadingRateKHR {
        VkStructureType       sType;
        void*                 pNext;
        VkSampleCountFlags    sampleCounts;
        VkExtent2D            fragmentSize;
    } VkPhysicalDeviceFragmentShadingRateKHR;

- `sType` is the type of this structure.

- `pNext` is `NULL` or a pointer to a structure extending this structure.

- `sampleCounts` is a bitmask of sample counts for which the shading rate described by `fragmentSize` is supported.

- `fragmentSize` is a VkExtent2D describing the width and height of a supported shading rate.

Valid Usage (Implicit)

- VUID-VkPhysicalDeviceFragmentShadingRateKHR-sType-sType
  `sType` must be `VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_FRAGMENT_SHADING_RATE_KHR`

- VUID-VkPhysicalDeviceFragmentShadingRateKHR-pNext-pNext
  `pNext` must be `NULL`

Fragment shading rates can be set at three points, with the three rates combined to determine the final shading rate.

#### 27.6.1. Pipeline Fragment Shading Rate

The pipeline fragment shading rate can be set on a per-draw basis by either setting the rate in a graphics pipeline, or dynamically via vkCmdSetFragmentShadingRateKHR.

The `VkPipelineFragmentShadingRateStateCreateInfoKHR` structure is defined as:

    // Provided by VK_KHR_fragment_shading_rate
    typedef struct VkPipelineFragmentShadingRateStateCreateInfoKHR {
        VkStructureType                       sType;
        const void*                           pNext;
        VkExtent2D                            fragmentSize;
        VkFragmentShadingRateCombinerOpKHR    combinerOps[2];
    } VkPipelineFragmentShadingRateStateCreateInfoKHR;

- `sType` is the type of this structure.

- `pNext` is `NULL` or a pointer to a structure extending this structure.

- `fragmentSize` specifies a VkExtent2D structure containing the fragment size used to define the pipeline fragment shading rate for drawing commands using this pipeline.

- `combinerOps` specifies a VkFragmentShadingRateCombinerOpKHR value determining how the pipeline, primitive, and attachment shading rates are combined for fragments generated by drawing commands using the created pipeline.

If the `pNext` chain of VkGraphicsPipelineCreateInfo includes a `VkPipelineFragmentShadingRateStateCreateInfoKHR` structure, then that structure includes parameters controlling the pipeline fragment shading rate.

If this structure is not present, `fragmentSize` is considered to be equal to (1,1), and both elements of `combinerOps` are considered to be equal to `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_KEEP_KHR`.

Valid Usage (Implicit)

- VUID-VkPipelineFragmentShadingRateStateCreateInfoKHR-sType-sType
  `sType` must be `VK_STRUCTURE_TYPE_PIPELINE_FRAGMENT_SHADING_RATE_STATE_CREATE_INFO_KHR`

To dynamically set the pipeline fragment shading rate and combiner operation, call:

    // Provided by VK_KHR_fragment_shading_rate
    void vkCmdSetFragmentShadingRateKHR(
        VkCommandBuffer                             commandBuffer,
        const VkExtent2D*                           pFragmentSize,
        const VkFragmentShadingRateCombinerOpKHR    combinerOps[2]);

- `commandBuffer` is the command buffer into which the command will be recorded.

- `pFragmentSize` specifies the pipeline fragment shading rate for subsequent drawing commands.

- `combinerOps` specifies a VkFragmentShadingRateCombinerOpKHR determining how the pipeline, primitive, and attachment shading rates are combined for fragments generated by subsequent drawing commands.

This command sets the pipeline fragment shading rate and combiner operation for subsequent drawing commands when the graphics pipeline is created with `VK_DYNAMIC_STATE_FRAGMENT_SHADING_RATE_KHR` set in VkPipelineDynamicStateCreateInfo::`pDynamicStates`. Otherwise, this state is specified by the VkPipelineFragmentShadingRateStateCreateInfoKHR values used to create the currently active pipeline.

Valid Usage

- VUID-vkCmdSetFragmentShadingRateKHR-pipelineFragmentShadingRate-04507
  If `pipelineFragmentShadingRate` is not enabled, `pFragmentSize->width` must be `1`

- VUID-vkCmdSetFragmentShadingRateKHR-pipelineFragmentShadingRate-04508
  If `pipelineFragmentShadingRate` is not enabled, `pFragmentSize->height` must be `1`

- VUID-vkCmdSetFragmentShadingRateKHR-pipelineFragmentShadingRate-04509
  One of `pipelineFragmentShadingRate`, `primitiveFragmentShadingRate`, or `attachmentFragmentShadingRate` must be enabled

- VUID-vkCmdSetFragmentShadingRateKHR-primitiveFragmentShadingRate-04510
  If the `primitiveFragmentShadingRate` feature is not enabled, `combinerOps`[0] must be `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_KEEP_KHR`

- VUID-vkCmdSetFragmentShadingRateKHR-attachmentFragmentShadingRate-04511
  If the `attachmentFragmentShadingRate` feature is not enabled, `combinerOps`[1] must be `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_KEEP_KHR`

- VUID-vkCmdSetFragmentShadingRateKHR-fragmentSizeNonTrivialCombinerOps-04512
  If the `fragmentSizeNonTrivialCombinerOps` limit is not supported, elements of `combinerOps` must be either `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_KEEP_KHR` or `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_REPLACE_KHR`

- VUID-vkCmdSetFragmentShadingRateKHR-pFragmentSize-04513
  `pFragmentSize->width` must be greater than or equal to `1`

- VUID-vkCmdSetFragmentShadingRateKHR-pFragmentSize-04514
  `pFragmentSize->height` must be greater than or equal to `1`

- VUID-vkCmdSetFragmentShadingRateKHR-pFragmentSize-04515
  `pFragmentSize->width` must be a power-of-two value

- VUID-vkCmdSetFragmentShadingRateKHR-pFragmentSize-04516
  `pFragmentSize->height` must be a power-of-two value

- VUID-vkCmdSetFragmentShadingRateKHR-pFragmentSize-04517
  `pFragmentSize->width` must be less than or equal to `4`

- VUID-vkCmdSetFragmentShadingRateKHR-pFragmentSize-04518
  `pFragmentSize->height` must be less than or equal to `4`

Valid Usage (Implicit)

- VUID-vkCmdSetFragmentShadingRateKHR-commandBuffer-parameter
  `commandBuffer` must be a valid VkCommandBuffer handle

- VUID-vkCmdSetFragmentShadingRateKHR-pFragmentSize-parameter
  `pFragmentSize` must be a valid pointer to a valid VkExtent2D structure

- VUID-vkCmdSetFragmentShadingRateKHR-combinerOps-parameter
  Any given element of `combinerOps` must be a valid VkFragmentShadingRateCombinerOpKHR value

- VUID-vkCmdSetFragmentShadingRateKHR-commandBuffer-recording
  `commandBuffer` must be in the recording state

- VUID-vkCmdSetFragmentShadingRateKHR-commandBuffer-cmdpool
  The `VkCommandPool` that `commandBuffer` was allocated from must support graphics operations

- VUID-vkCmdSetFragmentShadingRateKHR-videocoding
  This command must only be called outside of a video coding scope

Host Synchronization

- Host access to `commandBuffer` must be externally synchronized

- Host access to the `VkCommandPool` that `commandBuffer` was allocated from must be externally synchronized

Command Properties

Command Buffer Levels | Render Pass Scope | Video Coding Scope | Supported Queue Types
--- | --- | --- | ---
Primary Secondary | Both | Outside | Graphics

#### 27.6.2. Primitive Fragment Shading Rate

The primitive fragment shading rate can be set via the `PrimitiveShadingRateKHR` built-in in the last active pre-rasterization shader stage. If the last pre-rasterization shader stage is using the `MeshEXT` `Execution` `Model`, the rate associated with a given primitive is sourced from the value written to the per-primitive `PrimitiveShadingRateKHR`. Otherwise the rate associated with a given primitive is sourced from the value written to `PrimitiveShadingRateKHR` by that primitive’s provoking vertex.

#### 27.6.3. Attachment Fragment Shading Rate

The attachment shading rate can be set by including VkFragmentShadingRateAttachmentInfoKHR in a subpass to define a fragment shading rate attachment. Each pixel in the framebuffer is assigned an attachment fragment shading rate by the corresponding texel in the fragment shading rate attachment, according to:

  x' = floor(x / regionx)

  y' = floor(y / regiony)

where x' and y' are the coordinates of a texel in the fragment shading rate attachment, x and y are the coordinates of the pixel in the framebuffer, and regionx and regiony are the size of the region each texel corresponds to, as defined by the `shadingRateAttachmentTexelSize` member of VkFragmentShadingRateAttachmentInfoKHR.

If multiview is enabled and the shading rate attachment has multiple layers, the shading rate attachment texel is selected from the layer determined by the `ViewIndex` built-in. If multiview is disabled, and both the shading rate attachment and the framebuffer have multiple layers, the shading rate attachment texel is selected from the layer determined by the `Layer` built-in. Otherwise, the texel is unconditionally selected from the first layer of the attachment.

The fragment size is encoded into the first component of the identified texel as follows:

  sizew = 2((texel/4)&3)

  sizeh = 2(texel&3)

where texel is the value in the first component of the identified texel, and sizew and sizeh are the width and height of the fragment size, decoded from the texel.

If no fragment shading rate attachment is specified, this size is calculated as sizew = sizeh = 1. Applications must not specify a width or height greater than 4 by this method.

The Fragment Shading Rate enumeration in SPIR-V adheres to the above encoding.

#### 27.6.4. Combining the Fragment Shading Rates

The final rate (Cxy') used for fragment shading must be one of the rates returned by vkGetPhysicalDeviceFragmentShadingRatesKHR for the sample count and render pass transform used by rasterization.

If any of the following conditions are met, Cxy' must be set to {1,1}:

- If Sample Shading is enabled.

- The `fragmentShadingRateWithSampleMask` limit is not supported, and VkPipelineMultisampleStateCreateInfo::`pSampleMask` contains a zero value in any bit used by fragment operations.

- The `fragmentShadingRateWithShaderSampleMask` is not supported, and the fragment shader has `SampleMask` in the input or output interface.

- The `fragmentShadingRateWithShaderDepthStencilWrites` limit is not supported, and the fragment shader declares the `FragDepth` or `FragStencilRefEXT` built-in.

- The `fragmentShadingRateWithConservativeRasterization` limit is not supported, and VkPipelineRasterizationConservativeStateCreateInfoEXT::`conservativeRasterizationMode` is not `VK_CONSERVATIVE_RASTERIZATION_MODE_DISABLED_EXT`.

- The `fragmentShadingRateWithFragmentShaderInterlock` limit is not supported, and the fragment shader declares any of the fragment shader interlock execution modes.

- The `fragmentShadingRateWithCustomSampleLocations` limit is not supported, and VkPipelineSampleLocationsStateCreateInfoEXT::`sampleLocationsEnable` is `VK_TRUE`.

Otherwise, each of the specified shading rates are combined and then used to derive the value of Cxy'. As there are three ways to specify shading rates, two combiner operations are specified - between the pipeline and primitive shading rates, and between the result of that and the attachment shading rate.

The equation used for each combiner operation is defined by `VkFragmentShadingRateCombinerOpKHR`:

    // Provided by VK_KHR_fragment_shading_rate
    typedef enum VkFragmentShadingRateCombinerOpKHR {
        VK_FRAGMENT_SHADING_RATE_COMBINER_OP_KEEP_KHR = 0,
        VK_FRAGMENT_SHADING_RATE_COMBINER_OP_REPLACE_KHR = 1,
        VK_FRAGMENT_SHADING_RATE_COMBINER_OP_MIN_KHR = 2,
        VK_FRAGMENT_SHADING_RATE_COMBINER_OP_MAX_KHR = 3,
        VK_FRAGMENT_SHADING_RATE_COMBINER_OP_MUL_KHR = 4,
    } VkFragmentShadingRateCombinerOpKHR;

- `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_KEEP_KHR` specifies a combiner operation of combine(Axy,Bxy) = Axy.

- `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_REPLACE_KHR` specifies a combiner operation of combine(Axy,Bxy) = Bxy.

- `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_MIN_KHR` specifies a combiner operation of combine(Axy,Bxy) = min(Axy,Bxy).

- `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_MAX_KHR` specifies a combiner operation of combine(Axy,Bxy) = max(Axy,Bxy).

- `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_MUL_KHR` specifies a combiner operation of combine(Axy,Bxy) = Axy*Bxy.

where combine(Axy,Bxy) is the combine operation, and Axy and Bxy are the inputs to the operation.

If `fragmentShadingRateStrictMultiplyCombiner` is `VK_FALSE`, using `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_MUL_KHR` with values of 1 for both A and B in the same dimension results in the value 2 being produced for that dimension. See the definition of `fragmentShadingRateStrictMultiplyCombiner` for more information.

These operations are performed in a component-wise fashion.

This is used to generate a combined fragment area using the equation:

  Cxy = combine(Axy,Bxy)

where Cxy is the combined fragment area result, and Axy and Bxy are the fragment areas of the fragment shading rates being combined.

Two combine operations are performed, first with Axy equal to the pipeline fragment shading rate and Bxy equal to the primitive fragment shading rate, with the combine() operation selected by combinerOps[0]. A second combination is then performed, with Axy equal to the result of the first combination and Bxy equal to the attachment fragment shading rate, with the combine() operation selected by combinerOps[1]. The result of the second combination is used as the final fragment shading rate, reported via the `ShadingRateKHR` built-in.

Implementations may clamp the Cxy result of each combiner operation separately, or only after the second combiner operation.

If the final combined rate is one of the rates returned by vkGetPhysicalDeviceFragmentShadingRatesKHR for the sample count and render pass transform used by rasterization, Cxy' = Cxy. Otherwise, Cxy' is selected from the rates returned by vkGetPhysicalDeviceFragmentShadingRatesKHR for the sample count and render pass transform used by rasterization. From this list of supported rates, the following steps are applied in order, to select a single value:

1. Keep only rates where Cx' ≤ Cx and Cy' ≤ Cy.

   - Implementations may also keep rates where Cx' ≤ Cy and Cy' ≤ Cx.

2. Keep only rates with the highest area (Cx' × Cy').

3. Keep only rates with the lowest aspect ratio (Cx' + Cy').

4. In cases where a wide (e.g. 4x1) and tall (e.g. 1x4) rate remain, the implementation may choose either rate. However, it must choose this rate consistently for the same shading rates, render pass transform, and combiner operations for the lifetime of the VkDevice.

#### 27.6.5. Extended Fragment Shading Rates

The features advertised by VkPhysicalDeviceFragmentShadingRateEnumsFeaturesNV provide support for additional fragment shading rates beyond those specifying one fragment shader invocation covering all pixels in a fragment whose size is indicated by the fragment shading rate.

If the `fragmentShadingRateEnums` feature is enabled, fragment shading rates may be specified using the VkFragmentShadingRateNV enumerated type defined as:

    // Provided by VK_NV_fragment_shading_rate_enums
    typedef enum VkFragmentShadingRateNV {
        VK_FRAGMENT_SHADING_RATE_1_INVOCATION_PER_PIXEL_NV = 0,
        VK_FRAGMENT_SHADING_RATE_1_INVOCATION_PER_1X2_PIXELS_NV = 1,
        VK_FRAGMENT_SHADING_RATE_1_INVOCATION_PER_2X1_PIXELS_NV = 4,
        VK_FRAGMENT_SHADING_RATE_1_INVOCATION_PER_2X2_PIXELS_NV = 5,
        VK_FRAGMENT_SHADING_RATE_1_INVOCATION_PER_2X4_PIXELS_NV = 6,
        VK_FRAGMENT_SHADING_RATE_1_INVOCATION_PER_4X2_PIXELS_NV = 9,
        VK_FRAGMENT_SHADING_RATE_1_INVOCATION_PER_4X4_PIXELS_NV = 10,
        VK_FRAGMENT_SHADING_RATE_2_INVOCATIONS_PER_PIXEL_NV = 11,
        VK_FRAGMENT_SHADING_RATE_4_INVOCATIONS_PER_PIXEL_NV = 12,
        VK_FRAGMENT_SHADING_RATE_8_INVOCATIONS_PER_PIXEL_NV = 13,
        VK_FRAGMENT_SHADING_RATE_16_INVOCATIONS_PER_PIXEL_NV = 14,
        VK_FRAGMENT_SHADING_RATE_NO_INVOCATIONS_NV = 15,
    } VkFragmentShadingRateNV;

- `VK_FRAGMENT_SHADING_RATE_1_INVOCATION_PER_PIXEL_NV` specifies a fragment size of 1x1 pixels.

- `VK_FRAGMENT_SHADING_RATE_1_INVOCATION_PER_1X2_PIXELS_NV` specifies a fragment size of 1x2 pixels.

- `VK_FRAGMENT_SHADING_RATE_1_INVOCATION_PER_2X1_PIXELS_NV` specifies a fragment size of 2x1 pixels.

- `VK_FRAGMENT_SHADING_RATE_1_INVOCATION_PER_2X2_PIXELS_NV` specifies a fragment size of 2x2 pixels.

- `VK_FRAGMENT_SHADING_RATE_1_INVOCATION_PER_2X4_PIXELS_NV` specifies a fragment size of 2x4 pixels.

- `VK_FRAGMENT_SHADING_RATE_1_INVOCATION_PER_4X2_PIXELS_NV` specifies a fragment size of 4x2 pixels.

- `VK_FRAGMENT_SHADING_RATE_1_INVOCATION_PER_4X4_PIXELS_NV` specifies a fragment size of 4x4 pixels.

- `VK_FRAGMENT_SHADING_RATE_2_INVOCATIONS_PER_PIXEL_NV` specifies a fragment size of 1x1 pixels, with two fragment shader invocations per fragment.

- `VK_FRAGMENT_SHADING_RATE_4_INVOCATIONS_PER_PIXEL_NV` specifies a fragment size of 1x1 pixels, with four fragment shader invocations per fragment.

- `VK_FRAGMENT_SHADING_RATE_8_INVOCATIONS_PER_PIXEL_NV` specifies a fragment size of 1x1 pixels, with eight fragment shader invocations per fragment.

- `VK_FRAGMENT_SHADING_RATE_16_INVOCATIONS_PER_PIXEL_NV` specifies a fragment size of 1x1 pixels, with sixteen fragment shader invocations per fragment.

- `VK_FRAGMENT_SHADING_RATE_NO_INVOCATIONS_NV` specifies that any portions of a primitive that use that shading rate should be discarded without invoking any fragment shader.

To use the shading rates `VK_FRAGMENT_SHADING_RATE_2_INVOCATIONS_PER_PIXEL_NV`, `VK_FRAGMENT_SHADING_RATE_4_INVOCATIONS_PER_PIXEL_NV`, `VK_FRAGMENT_SHADING_RATE_8_INVOCATIONS_PER_PIXEL_NV`, and `VK_FRAGMENT_SHADING_RATE_16_INVOCATIONS_PER_PIXEL_NV` as a pipeline, primitive, or attachment shading rate, the `supersampleFragmentShadingRates` feature must be enabled. To use the shading rate `VK_FRAGMENT_SHADING_RATE_NO_INVOCATIONS_NV` as a pipeline, primitive, or attachment shading rate, the `noInvocationFragmentShadingRates` feature must be enabled.

When using fragment shading rate enums, the pipeline fragment shading rate can be set on a per-draw basis by either setting the rate in a graphics pipeline, or dynamically via vkCmdSetFragmentShadingRateEnumNV.

The `VkPipelineFragmentShadingRateEnumStateCreateInfoNV` structure is defined as:

    // Provided by VK_NV_fragment_shading_rate_enums
    typedef struct VkPipelineFragmentShadingRateEnumStateCreateInfoNV {
        VkStructureType                       sType;
        const void*                           pNext;
        VkFragmentShadingRateTypeNV           shadingRateType;
        VkFragmentShadingRateNV               shadingRate;
        VkFragmentShadingRateCombinerOpKHR    combinerOps[2];
    } VkPipelineFragmentShadingRateEnumStateCreateInfoNV;

- `sType` is the type of this structure.

- `pNext` is `NULL` or a pointer to a structure extending this structure.

- `shadingRateType` specifies a VkFragmentShadingRateTypeNV value indicating whether fragment shading rates are specified using fragment sizes or VkFragmentShadingRateNV enums.

- `shadingRate` specifies a VkFragmentShadingRateNV value indicating the pipeline fragment shading rate.

- `combinerOps` specifies VkFragmentShadingRateCombinerOpKHR values determining how the pipeline, primitive, and attachment shading rates are combined for fragments generated by drawing commands using the created pipeline.

If the `pNext` chain of VkGraphicsPipelineCreateInfo includes a `VkPipelineFragmentShadingRateEnumStateCreateInfoNV` structure, then that structure includes parameters controlling the pipeline fragment shading rate.

If this structure is not present, `shadingRateType` is considered to be equal to `VK_FRAGMENT_SHADING_RATE_TYPE_FRAGMENT_SIZE_NV`, `shadingRate` is considered to be equal to `VK_FRAGMENT_SHADING_RATE_1_INVOCATION_PER_PIXEL_NV`, and both elements of `combinerOps` are considered to be equal to `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_KEEP_KHR`.

Valid Usage (Implicit)

- VUID-VkPipelineFragmentShadingRateEnumStateCreateInfoNV-sType-sType
  `sType` must be `VK_STRUCTURE_TYPE_PIPELINE_FRAGMENT_SHADING_RATE_ENUM_STATE_CREATE_INFO_NV`

The VkFragmentShadingRateTypeNV enumerated type specifies whether a graphics pipeline gets its pipeline fragment shading rates and combiners from the VkPipelineFragmentShadingRateEnumStateCreateInfoNV structure or the VkPipelineFragmentShadingRateStateCreateInfoKHR structure.

    // Provided by VK_NV_fragment_shading_rate_enums
    typedef enum VkFragmentShadingRateTypeNV {
        VK_FRAGMENT_SHADING_RATE_TYPE_FRAGMENT_SIZE_NV = 0,
        VK_FRAGMENT_SHADING_RATE_TYPE_ENUMS_NV = 1,
    } VkFragmentShadingRateTypeNV;

- `VK_FRAGMENT_SHADING_RATE_TYPE_FRAGMENT_SIZE_NV` specifies that a graphics pipeline should obtain its pipeline fragment shading rate and shading rate combiner state from the VkPipelineFragmentShadingRateStateCreateInfoKHR structure and that any state specified by the VkPipelineFragmentShadingRateEnumStateCreateInfoNV structure should be ignored.

- `VK_FRAGMENT_SHADING_RATE_TYPE_ENUMS_NV` specifies that a graphics pipeline should obtain its pipeline fragment shading rate and shading rate combiner state from the VkPipelineFragmentShadingRateEnumStateCreateInfoNV structure and that any state specified by the VkPipelineFragmentShadingRateStateCreateInfoKHR structure should be ignored.

To dynamically set the pipeline fragment shading rate and combiner operation, call:

    // Provided by VK_NV_fragment_shading_rate_enums
    void vkCmdSetFragmentShadingRateEnumNV(
        VkCommandBuffer                             commandBuffer,
        VkFragmentShadingRateNV                     shadingRate,
        const VkFragmentShadingRateCombinerOpKHR    combinerOps[2]);

- `commandBuffer` is the command buffer into which the command will be recorded.

- `shadingRate` specifies a VkFragmentShadingRateNV enum indicating the pipeline fragment shading rate for subsequent drawing commands.

- `combinerOps` specifies a VkFragmentShadingRateCombinerOpKHR determining how the pipeline, primitive, and attachment shading rates are combined for fragments generated by subsequent drawing commands.

This command sets the pipeline fragment shading rate and combiner operation for subsequent drawing commands when the graphics pipeline is created with `VK_DYNAMIC_STATE_FRAGMENT_SHADING_RATE_KHR` set in VkPipelineDynamicStateCreateInfo::`pDynamicStates`. Otherwise, this state is specified by the VkPipelineFragmentShadingRateEnumStateCreateInfoNV values used to create the currently active pipeline.

| Note This command allows specifying additional shading rates beyond those supported by vkCmdSetFragmentShadingRateKHR. For more information, refer to the `VK_NV_fragment_shading_rate_enums` appendix.

Valid Usage

- VUID-vkCmdSetFragmentShadingRateEnumNV-pipelineFragmentShadingRate-04576
  If `pipelineFragmentShadingRate` is not enabled, `shadingRate` must be `VK_FRAGMENT_SHADING_RATE_1_INVOCATION_PER_PIXEL_NV`

- VUID-vkCmdSetFragmentShadingRateEnumNV-supersampleFragmentShadingRates-04577
  If `supersampleFragmentShadingRates` is not enabled, `shadingRate` must not be `VK_FRAGMENT_SHADING_RATE_2_INVOCATIONS_PER_PIXEL_NV`, `VK_FRAGMENT_SHADING_RATE_4_INVOCATIONS_PER_PIXEL_NV`, `VK_FRAGMENT_SHADING_RATE_8_INVOCATIONS_PER_PIXEL_NV`, or `VK_FRAGMENT_SHADING_RATE_16_INVOCATIONS_PER_PIXEL_NV`

- VUID-vkCmdSetFragmentShadingRateEnumNV-noInvocationFragmentShadingRates-04578
  If `noInvocationFragmentShadingRates` is not enabled, `shadingRate` must not be `VK_FRAGMENT_SHADING_RATE_NO_INVOCATIONS_NV`

- VUID-vkCmdSetFragmentShadingRateEnumNV-fragmentShadingRateEnums-04579
  The `fragmentShadingRateEnums` feature must be enabled

- VUID-vkCmdSetFragmentShadingRateEnumNV-pipelineFragmentShadingRate-04580
  One of the `pipelineFragmentShadingRate`, `primitiveFragmentShadingRate`, or `attachmentFragmentShadingRate` features must be enabled

- VUID-vkCmdSetFragmentShadingRateEnumNV-primitiveFragmentShadingRate-04581
  If the `primitiveFragmentShadingRate` feature is not enabled, `combinerOps`[0] must be `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_KEEP_KHR`

- VUID-vkCmdSetFragmentShadingRateEnumNV-attachmentFragmentShadingRate-04582
  If the `attachmentFragmentShadingRate` feature is not enabled, `combinerOps`[1] must be `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_KEEP_KHR`

- VUID-vkCmdSetFragmentShadingRateEnumNV-fragmentSizeNonTrivialCombinerOps-04583
  If the `fragmentSizeNonTrivialCombinerOps` limit is not supported, elements of `combinerOps` must be either `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_KEEP_KHR` or `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_REPLACE_KHR`

Valid Usage (Implicit)

- VUID-vkCmdSetFragmentShadingRateEnumNV-commandBuffer-parameter
  `commandBuffer` must be a valid VkCommandBuffer handle

- VUID-vkCmdSetFragmentShadingRateEnumNV-shadingRate-parameter
  `shadingRate` must be a valid VkFragmentShadingRateNV value

- VUID-vkCmdSetFragmentShadingRateEnumNV-combinerOps-parameter
  Any given element of `combinerOps` must be a valid VkFragmentShadingRateCombinerOpKHR value

- VUID-vkCmdSetFragmentShadingRateEnumNV-commandBuffer-recording
  `commandBuffer` must be in the recording state

- VUID-vkCmdSetFragmentShadingRateEnumNV-commandBuffer-cmdpool
  The `VkCommandPool` that `commandBuffer` was allocated from must support graphics operations

- VUID-vkCmdSetFragmentShadingRateEnumNV-videocoding
  This command must only be called outside of a video coding scope

Host Synchronization

- Host access to `commandBuffer` must be externally synchronized

- Host access to the `VkCommandPool` that `commandBuffer` was allocated from must be externally synchronized

Command Properties

Command Buffer Levels | Render Pass Scope | Video Coding Scope | Supported Queue Types
--- | --- | --- | ---
Primary Secondary | Both | Outside | Graphics

When the `supersampleFragmentShadingRates` or `noInvocationFragmentShadingRates` features are enabled, the behavior of the shading rate combiner operations is extended to support the shading rates enabled by those features. Primitive and attachment shading rate values are interpreted as VkFragmentShadingRateNV values and the behavior of the combiners is modified as follows:

- For `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_MIN_KHR`, `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_MAX_KHR`, and `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_MUL_KHR`, if either Axy or Bxy is `VK_FRAGMENT_SHADING_RATE_NO_INVOCATIONS_NV`, combine(Axy,Bxy) produces a shading rate of `VK_FRAGMENT_SHADING_RATE_NO_INVOCATIONS_NV`, regardless of the other input shading rate.

- For `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_MIN_KHR`, combine(Axy,Bxy) produces a shading rate whose fragment size is the smaller of the fragment sizes of Axy and Bxy and whose invocation count is the larger of the invocation counts of Axy and Bxy.

- For `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_MAX_KHR`, combine(Axy,Bxy) produces a shading rate whose fragment size is the larger of the fragment sizes of Axy and Bxy and whose invocation count is the smaller of the invocation counts of Axy and Bxy.

- For `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_MUL_KHR`, combine(Axy,Bxy) produces a shading rate whose fragment size and invocation count is the product of the fragment sizes and invocation counts, respectively, of Axy and Bxy. If the resulting shading rate has both multiple pixels and multiple invocations per fragment, an implementation may adjust the shading rate by reducing both the pixel and invocation counts.

If the final shading rate from the combiners is `VK_FRAGMENT_SHADING_RATE_NO_INVOCATIONS_NV`, no fragments will be generated for any portion of a primitive using that shading rate.

If the final shading rate from the combiners specifies multiple fragment shader invocations per fragment, the fragment will be processed with multiple unique samples as in sample shading, where the total number the total number of invocations is taken from the shading rate and then clamped to `rasterizationSamples` and `maxFragmentShadingRateInvocationCount`.

### 27.7. Shading Rate Image

The `shadingRateImage` feature allows pipelines to use a shading rate image to control the fragment area and the minimum number of fragment shader invocations launched for each fragment. When the shading rate image is enabled, the rasterizer determines a base shading rate for each region of the framebuffer covered by a primitive by fetching a value from the shading rate image and translating it to a shading rate using a per-viewport shading rate palette. This base shading rate is then adjusted to derive a final shading rate. The final shading rate specifies the fragment area and fragment shader invocation count to use for fragments generated in the region.

If the `pNext` chain of VkPipelineViewportStateCreateInfo includes a `VkPipelineViewportShadingRateImageStateCreateInfoNV` structure, then that structure includes parameters controlling the shading rate.

The `VkPipelineViewportShadingRateImageStateCreateInfoNV` structure is defined as:

    // Provided by VK_NV_shading_rate_image
    typedef struct VkPipelineViewportShadingRateImageStateCreateInfoNV {
        VkStructureType                  sType;
        const void*                      pNext;
        VkBool32                         shadingRateImageEnable;
        uint32_t                         viewportCount;
        const VkShadingRatePaletteNV*    pShadingRatePalettes;
    } VkPipelineViewportShadingRateImageStateCreateInfoNV;

- `sType` is the type of this structure.

- `pNext` is `NULL` or a pointer to a structure extending this structure.

- `shadingRateImageEnable` specifies whether shading rate image and palettes are used during rasterization.

- `viewportCount` specifies the number of per-viewport palettes used to translate values stored in shading rate images.

- `pShadingRatePalettes` is a pointer to an array of VkShadingRatePaletteNV structures defining the palette for each viewport. If the shading rate palette state is dynamic, this member is ignored.

If this structure is not present, `shadingRateImageEnable` is considered to be `VK_FALSE`, and the shading rate image and palettes are not used.

Valid Usage

- VUID-VkPipelineViewportShadingRateImageStateCreateInfoNV-viewportCount-02054
  If the `multiViewport` feature is not enabled, `viewportCount` must be `0` or `1`

- VUID-VkPipelineViewportShadingRateImageStateCreateInfoNV-viewportCount-02055
  `viewportCount` must be less than or equal to `VkPhysicalDeviceLimits`::`maxViewports`

- VUID-VkPipelineViewportShadingRateImageStateCreateInfoNV-shadingRateImageEnable-02056
  If `shadingRateImageEnable` is `VK_TRUE`, `viewportCount` must be greater or equal to the `viewportCount` member of VkPipelineViewportStateCreateInfo

Valid Usage (Implicit)

- VUID-VkPipelineViewportShadingRateImageStateCreateInfoNV-sType-sType
  `sType` must be `VK_STRUCTURE_TYPE_PIPELINE_VIEWPORT_SHADING_RATE_IMAGE_STATE_CREATE_INFO_NV`

When shading rate image usage is enabled in the bound pipeline, the pipeline uses a shading rate image specified by the command:

    // Provided by VK_NV_shading_rate_image
    void vkCmdBindShadingRateImageNV(
        VkCommandBuffer                             commandBuffer,
        VkImageView                                 imageView,
        VkImageLayout                               imageLayout);

- `commandBuffer` is the command buffer into which the command will be recorded.

- `imageView` is an image view handle specifying the shading rate image. `imageView` may be set to VK_NULL_HANDLE, which is equivalent to specifying a view of an image filled with zero values.

- `imageLayout` is the layout that the image subresources accessible from `imageView` will be in when the shading rate image is accessed.

Valid Usage

- VUID-vkCmdBindShadingRateImageNV-None-02058
  The `shadingRateImage` feature must be enabled

- VUID-vkCmdBindShadingRateImageNV-imageView-02059
  If `imageView` is not VK_NULL_HANDLE, it must be a valid VkImageView handle of type `VK_IMAGE_VIEW_TYPE_2D` or `VK_IMAGE_VIEW_TYPE_2D_ARRAY`

- VUID-vkCmdBindShadingRateImageNV-imageView-02060
  If `imageView` is not VK_NULL_HANDLE, it must have a format of `VK_FORMAT_R8_UINT`

- VUID-vkCmdBindShadingRateImageNV-imageView-02061
  If `imageView` is not VK_NULL_HANDLE, it must have been created with a `usage` value including `VK_IMAGE_USAGE_SHADING_RATE_IMAGE_BIT_NV`

- VUID-vkCmdBindShadingRateImageNV-imageView-02062
  If `imageView` is not VK_NULL_HANDLE, `imageLayout` must match the actual VkImageLayout of each subresource accessible from `imageView` at the time the subresource is accessed

- VUID-vkCmdBindShadingRateImageNV-imageLayout-02063
  If `imageView` is not VK_NULL_HANDLE, `imageLayout` must be `VK_IMAGE_LAYOUT_SHADING_RATE_OPTIMAL_NV` or `VK_IMAGE_LAYOUT_GENERAL`

Valid Usage (Implicit)

- VUID-vkCmdBindShadingRateImageNV-commandBuffer-parameter
  `commandBuffer` must be a valid VkCommandBuffer handle

- VUID-vkCmdBindShadingRateImageNV-imageView-parameter
  If `imageView` is not VK_NULL_HANDLE, `imageView` must be a valid VkImageView handle

- VUID-vkCmdBindShadingRateImageNV-imageLayout-parameter
  `imageLayout` must be a valid VkImageLayout value

- VUID-vkCmdBindShadingRateImageNV-commandBuffer-recording
  `commandBuffer` must be in the recording state

- VUID-vkCmdBindShadingRateImageNV-commandBuffer-cmdpool
  The `VkCommandPool` that `commandBuffer` was allocated from must support graphics operations

- VUID-vkCmdBindShadingRateImageNV-videocoding
  This command must only be called outside of a video coding scope

- VUID-vkCmdBindShadingRateImageNV-commonparent
  Both of `commandBuffer`, and `imageView` that are valid handles of non-ignored parameters must have been created, allocated, or retrieved from the same VkDevice

Host Synchronization

- Host access to `commandBuffer` must be externally synchronized

- Host access to the `VkCommandPool` that `commandBuffer` was allocated from must be externally synchronized

Command Properties

Command Buffer Levels | Render Pass Scope | Video Coding Scope | Supported Queue Types
--- | --- | --- | ---
Primary Secondary | Both | Outside | Graphics

When the shading rate image is enabled in the current pipeline, rasterizing a primitive covering the pixel with coordinates (x,y) will fetch a shading rate index value from the shading rate image bound by `vkCmdBindShadingRateImageNV`. If the shading rate image view has a type of `VK_IMAGE_VIEW_TYPE_2D`, the lookup will use texel coordinates (u,v) where u=⌊t w idth x​⌋, v=⌊thei g ht y​⌋, and t w idth and thei g ht are the width and height of the implementation-dependent shading rate texel size. If the shading rate image view has a type of `VK_IMAGE_VIEW_TYPE_2D_ARRAY`, the lookup will use texel coordinates (u,v) to extract a texel from the layer l, where l is the layer of the framebuffer being rendered to. If l is greater than or equal to the number of layers in the image view, layer zero will be used.

If the bound shading rate image view is not VK_NULL_HANDLE and contains a texel with coordinates (u,v) in layer l (if applicable), the single unsigned integer component for that texel will be used as the shading rate index. If the (u,v) coordinate is outside the extents of the subresource used by the shading rate image view, or if the image view is VK_NULL_HANDLE, the shading rate index is zero. If the shading rate image view has multiple mipmap levels, the base level identified by `VkImageSubresourceRange`::`baseMipLevel` will be used.

A shading rate index is mapped to a base shading rate using a lookup table called the shading rate image palette. There is a separate palette for each viewport. The number of entries in each palette is given by the implementation-dependent shading rate image palette size.

To dynamically set the per-viewport shading rate image palettes, call:

    // Provided by VK_NV_shading_rate_image
    void vkCmdSetViewportShadingRatePaletteNV(
        VkCommandBuffer                             commandBuffer,
        uint32_t                                    firstViewport,
        uint32_t                                    viewportCount,
        const VkShadingRatePaletteNV*               pShadingRatePalettes);

- `commandBuffer` is the command buffer into which the command will be recorded.

- `firstViewport` is the index of the first viewport whose shading rate palette is updated by the command.

- `viewportCount` is the number of viewports whose shading rate palettes are updated by the command.

- `pShadingRatePalettes` is a pointer to an array of VkShadingRatePaletteNV structures defining the palette for each viewport.

This command sets the per-viewport shading rate image palettes for subsequent drawing commands when the graphics pipeline is created with `VK_DYNAMIC_STATE_VIEWPORT_SHADING_RATE_PALETTE_NV` set in VkPipelineDynamicStateCreateInfo::`pDynamicStates`. Otherwise, this state is specified by the VkPipelineViewportShadingRateImageStateCreateInfoNV::`pShadingRatePalettes` values used to create the currently active pipeline.

Valid Usage

- VUID-vkCmdSetViewportShadingRatePaletteNV-None-02064
  The `shadingRateImage` feature must be enabled

- VUID-vkCmdSetViewportShadingRatePaletteNV-firstViewport-02067
  The sum of `firstViewport` and `viewportCount` must be between `1` and `VkPhysicalDeviceLimits`::`maxViewports`, inclusive

- VUID-vkCmdSetViewportShadingRatePaletteNV-firstViewport-02068
  If the `multiViewport` feature is not enabled, `firstViewport` must be `0`

- VUID-vkCmdSetViewportShadingRatePaletteNV-viewportCount-02069
  If the `multiViewport` feature is not enabled, `viewportCount` must be `1`

Valid Usage (Implicit)

- VUID-vkCmdSetViewportShadingRatePaletteNV-commandBuffer-parameter
  `commandBuffer` must be a valid VkCommandBuffer handle

- VUID-vkCmdSetViewportShadingRatePaletteNV-pShadingRatePalettes-parameter
  `pShadingRatePalettes` must be a valid pointer to an array of `viewportCount` valid VkShadingRatePaletteNV structures

- VUID-vkCmdSetViewportShadingRatePaletteNV-commandBuffer-recording
  `commandBuffer` must be in the recording state

- VUID-vkCmdSetViewportShadingRatePaletteNV-commandBuffer-cmdpool
  The `VkCommandPool` that `commandBuffer` was allocated from must support graphics operations

- VUID-vkCmdSetViewportShadingRatePaletteNV-videocoding
  This command must only be called outside of a video coding scope

- VUID-vkCmdSetViewportShadingRatePaletteNV-viewportCount-arraylength
  `viewportCount` must be greater than `0`

Host Synchronization

- Host access to `commandBuffer` must be externally synchronized

- Host access to the `VkCommandPool` that `commandBuffer` was allocated from must be externally synchronized

Command Properties

Command Buffer Levels | Render Pass Scope | Video Coding Scope | Supported Queue Types
--- | --- | --- | ---
Primary Secondary | Both | Outside | Graphics

The `VkShadingRatePaletteNV` structure specifies to contents of a single shading rate image palette and is defined as:

    // Provided by VK_NV_shading_rate_image
    typedef struct VkShadingRatePaletteNV {
        uint32_t                              shadingRatePaletteEntryCount;
        const VkShadingRatePaletteEntryNV*    pShadingRatePaletteEntries;
    } VkShadingRatePaletteNV;

- `shadingRatePaletteEntryCount` specifies the number of entries in the shading rate image palette.

- `pShadingRatePaletteEntries` is a pointer to an array of VkShadingRatePaletteEntryNV enums defining the shading rate for each palette entry.

Valid Usage

- VUID-VkShadingRatePaletteNV-shadingRatePaletteEntryCount-02071
  `shadingRatePaletteEntryCount` must be between `1` and `VkPhysicalDeviceShadingRateImagePropertiesNV`::`shadingRatePaletteSize`, inclusive

Valid Usage (Implicit)

- VUID-VkShadingRatePaletteNV-pShadingRatePaletteEntries-parameter
  `pShadingRatePaletteEntries` must be a valid pointer to an array of `shadingRatePaletteEntryCount` valid VkShadingRatePaletteEntryNV values

- VUID-VkShadingRatePaletteNV-shadingRatePaletteEntryCount-arraylength
  `shadingRatePaletteEntryCount` must be greater than `0`

To determine the base shading rate image, a shading rate index i is mapped to array element i in the array `pShadingRatePaletteEntries` for the palette corresponding to the viewport used for the fragment. If i is greater than or equal to the palette size `shadingRatePaletteEntryCount`, the base shading rate is undefined.

The supported shading rate image palette entries are defined by VkShadingRatePaletteEntryNV:

    // Provided by VK_NV_shading_rate_image
    typedef enum VkShadingRatePaletteEntryNV {
        VK_SHADING_RATE_PALETTE_ENTRY_NO_INVOCATIONS_NV = 0,
        VK_SHADING_RATE_PALETTE_ENTRY_16_INVOCATIONS_PER_PIXEL_NV = 1,
        VK_SHADING_RATE_PALETTE_ENTRY_8_INVOCATIONS_PER_PIXEL_NV = 2,
        VK_SHADING_RATE_PALETTE_ENTRY_4_INVOCATIONS_PER_PIXEL_NV = 3,
        VK_SHADING_RATE_PALETTE_ENTRY_2_INVOCATIONS_PER_PIXEL_NV = 4,
        VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_PIXEL_NV = 5,
        VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_2X1_PIXELS_NV = 6,
        VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_1X2_PIXELS_NV = 7,
        VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_2X2_PIXELS_NV = 8,
        VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_4X2_PIXELS_NV = 9,
        VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_2X4_PIXELS_NV = 10,
        VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_4X4_PIXELS_NV = 11,
    } VkShadingRatePaletteEntryNV;

The following table indicates the width and height (in pixels) of each fragment generated using the indicated shading rate, as well as the maximum number of fragment shader invocations launched for each fragment. When processing regions of a primitive that have a shading rate of `VK_SHADING_RATE_PALETTE_ENTRY_NO_INVOCATIONS_NV`, no fragments will be generated in that region.

Shading Rate | Width | Height | Invocations
--- | --- | --- | ---
`VK_SHADING_RATE_PALETTE_ENTRY_NO_INVOCATIONS_NV` | 0 | 0 | 0
`VK_SHADING_RATE_PALETTE_ENTRY_16_INVOCATIONS_PER_PIXEL_NV` | 1 | 1 | 16
`VK_SHADING_RATE_PALETTE_ENTRY_8_INVOCATIONS_PER_PIXEL_NV` | 1 | 1 | 8
`VK_SHADING_RATE_PALETTE_ENTRY_4_INVOCATIONS_PER_PIXEL_NV` | 1 | 1 | 4
`VK_SHADING_RATE_PALETTE_ENTRY_2_INVOCATIONS_PER_PIXEL_NV` | 1 | 1 | 2
`VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_PIXEL_NV` | 1 | 1 | 1
`VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_2X1_PIXELS_NV` | 2 | 1 | 1
`VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_1X2_PIXELS_NV` | 1 | 2 | 1
`VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_2X2_PIXELS_NV` | 2 | 2 | 1
`VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_4X2_PIXELS_NV` | 4 | 2 | 1
`VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_2X4_PIXELS_NV` | 2 | 4 | 1
`VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_4X4_PIXELS_NV` | 4 | 4 | 1

When the shading rate image is disabled, a shading rate of `VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_PIXEL_NV` will be used as the base shading rate.

Once a base shading rate has been established, it is adjusted to produce a final shading rate. First, if the base shading rate uses multiple pixels for each fragment, the implementation may reduce the fragment area to ensure that the total number of coverage samples for all pixels in a fragment does not exceed an implementation-dependent maximum.

If sample shading is active in the current pipeline and would result in processing n (n > 1) unique samples per fragment when the shading rate image is disabled, the shading rate is adjusted in an implementation-dependent manner to increase the number of fragment shader invocations spawned by the primitive. If the shading rate indicates fs pixels per fragment and fs is greater than n, the fragment area is adjusted so each fragment has approximately n f s​ pixels. Otherwise, if the shading rate indicates ipf invocations per fragment, the fragment area will be adjusted to a single pixel with approximately f s ip f×n​ invocations per fragment.

If sample shading occurs due to the use of a fragment shader input variable decorated with `SampleId` or `SamplePosition`, the shading rate is ignored. Each fragment will have a single pixel and will spawn up to `rasterizationSamples` fragment shader invocations, as when using sample shading without a shading rate image.

Finally, if the shading rate specifies multiple fragment shader invocations per fragment, the total number of invocations in the shading rate is clamped to be no larger than `rasterizationSamples`.

When the final shading rate for a primitive covering pixel (x,y) has a fragment area of f w×f h, the fragment for that pixel will cover all pixels with coordinates (x',y') that satisfy the equations:

⌊f w x​⌋=⌊f w x′​⌋​
⌊f h y​⌋=⌊f h y′​⌋​

This combined fragment is considered to have multiple coverage samples; the total number of samples in this fragment is given by samp l es=f w×f h×r s where rs indicates the value of `VkPipelineMultisampleStateCreateInfo`::`rasterizationSamples` specified at pipeline creation time. The set of coverage samples in the fragment is the union of the per-pixel coverage samples in each of the fragment’s pixels The location and order of coverage samples within each pixel in the combined fragment are assigned as described in Multisampling and Custom Sample Locations. Each coverage sample in the set of pixels belonging to the combined fragment is assigned a unique coverage index in the range [0,samples-1]. If the `shadingRateCoarseSampleOrder` feature is supported, the order of coverage samples can be specified for each combination of fragment area and coverage sample count. If this feature is not supported, the sample order is implementation-dependent.

If the `pNext` chain of VkPipelineViewportStateCreateInfo includes a `VkPipelineViewportCoarseSampleOrderStateCreateInfoNV` structure, then that structure includes parameters controlling the order of coverage samples in fragments larger than one pixel.

The `VkPipelineViewportCoarseSampleOrderStateCreateInfoNV` structure is defined as:

    // Provided by VK_NV_shading_rate_image
    typedef struct VkPipelineViewportCoarseSampleOrderStateCreateInfoNV {
        VkStructureType                       sType;
        const void*                           pNext;
        VkCoarseSampleOrderTypeNV             sampleOrderType;
        uint32_t                              customSampleOrderCount;
        const VkCoarseSampleOrderCustomNV*    pCustomSampleOrders;
    } VkPipelineViewportCoarseSampleOrderStateCreateInfoNV;

- `sType` is the type of this structure.

- `pNext` is `NULL` or a pointer to a structure extending this structure.

- `sampleOrderType` specifies the mechanism used to order coverage samples in fragments larger than one pixel.

- `customSampleOrderCount` specifies the number of custom sample orderings to use when ordering coverage samples.

- `pCustomSampleOrders` is a pointer to an array of `customSampleOrderCount` VkCoarseSampleOrderCustomNV structures, each structure specifying the coverage sample order for a single combination of fragment area and coverage sample count.

If this structure is not present, `sampleOrderType` is considered to be `VK_COARSE_SAMPLE_ORDER_TYPE_DEFAULT_NV`.

If `sampleOrderType` is `VK_COARSE_SAMPLE_ORDER_TYPE_CUSTOM_NV`, the coverage sample order used for any combination of fragment area and coverage sample count not enumerated in `pCustomSampleOrders` will be identical to that used for `VK_COARSE_SAMPLE_ORDER_TYPE_DEFAULT_NV`.

If the pipeline was created with `VK_DYNAMIC_STATE_VIEWPORT_COARSE_SAMPLE_ORDER_NV`, the contents of this structure (if present) are ignored, and the coverage sample order is instead specified by vkCmdSetCoarseSampleOrderNV.

Valid Usage

- VUID-VkPipelineViewportCoarseSampleOrderStateCreateInfoNV-sampleOrderType-02072
  If `sampleOrderType` is not `VK_COARSE_SAMPLE_ORDER_TYPE_CUSTOM_NV`, `customSamplerOrderCount` must be `0`

- VUID-VkPipelineViewportCoarseSampleOrderStateCreateInfoNV-pCustomSampleOrders-02234
  The array `pCustomSampleOrders` must not contain two structures with matching values for both the `shadingRate` and `sampleCount` members

Valid Usage (Implicit)

- VUID-VkPipelineViewportCoarseSampleOrderStateCreateInfoNV-sType-sType
  `sType` must be `VK_STRUCTURE_TYPE_PIPELINE_VIEWPORT_COARSE_SAMPLE_ORDER_STATE_CREATE_INFO_NV`

- VUID-VkPipelineViewportCoarseSampleOrderStateCreateInfoNV-sampleOrderType-parameter
  `sampleOrderType` must be a valid VkCoarseSampleOrderTypeNV value

- VUID-VkPipelineViewportCoarseSampleOrderStateCreateInfoNV-pCustomSampleOrders-parameter
  If `customSampleOrderCount` is not `0`, `pCustomSampleOrders` must be a valid pointer to an array of `customSampleOrderCount` valid VkCoarseSampleOrderCustomNV structures

The type VkCoarseSampleOrderTypeNV specifies the technique used to order coverage samples in fragments larger than one pixel, and is defined as:

    // Provided by VK_NV_shading_rate_image
    typedef enum VkCoarseSampleOrderTypeNV {
        VK_COARSE_SAMPLE_ORDER_TYPE_DEFAULT_NV = 0,
        VK_COARSE_SAMPLE_ORDER_TYPE_CUSTOM_NV = 1,
        VK_COARSE_SAMPLE_ORDER_TYPE_PIXEL_MAJOR_NV = 2,
        VK_COARSE_SAMPLE_ORDER_TYPE_SAMPLE_MAJOR_NV = 3,
    } VkCoarseSampleOrderTypeNV;

- `VK_COARSE_SAMPLE_ORDER_TYPE_DEFAULT_NV` specifies that coverage samples will be ordered in an implementation-dependent manner.

- `VK_COARSE_SAMPLE_ORDER_TYPE_CUSTOM_NV` specifies that coverage samples will be ordered according to the array of custom orderings provided in either the `pCustomSampleOrders` member of `VkPipelineViewportCoarseSampleOrderStateCreateInfoNV` or the `pCustomSampleOrders` member of vkCmdSetCoarseSampleOrderNV.

- `VK_COARSE_SAMPLE_ORDER_TYPE_PIXEL_MAJOR_NV` specifies that coverage samples will be ordered sequentially, sorted first by pixel coordinate (in row-major order) and then by sample index.

- `VK_COARSE_SAMPLE_ORDER_TYPE_SAMPLE_MAJOR_NV` specifies that coverage samples will be ordered sequentially, sorted first by sample index and then by pixel coordinate (in row-major order).

When using a coarse sample order of `VK_COARSE_SAMPLE_ORDER_TYPE_PIXEL_MAJOR_NV` for a fragment with an upper-left corner of (f x, f y) with a width of f w×f h and f sc samples per pixel, coverage index cs of the fragment will be assigned to sample index f s of pixel (px, p y) as follows:

px=p y=f s=​f x+(⌊f sc cs​⌋ % f w)f y+⌊f sc×f w cs​⌋cs % f sc​

When using a coarse sample order of `VK_COARSE_SAMPLE_ORDER_TYPE_SAMPLE_MAJOR_NV`, coverage index cs will be assigned as follows:

px=p y=f s=​f x+cs % f w(f y+⌊f w cs​⌋ % f h)⌊f w×f h cs​⌋​

The `VkCoarseSampleOrderCustomNV` structure is defined as:

    // Provided by VK_NV_shading_rate_image
    typedef struct VkCoarseSampleOrderCustomNV {
        VkShadingRatePaletteEntryNV        shadingRate;
        uint32_t                           sampleCount;
        uint32_t                           sampleLocationCount;
        const VkCoarseSampleLocationNV*    pSampleLocations;
    } VkCoarseSampleOrderCustomNV;

- `shadingRate` is a shading rate palette entry that identifies the fragment width and height for the combination of fragment area and per-pixel coverage sample count to control.

- `sampleCount` identifies the per-pixel coverage sample count for the combination of fragment area and coverage sample count to control.

- `sampleLocationCount` specifies the number of sample locations in the custom ordering.

- `pSampleLocations` is a pointer to an array of VkCoarseSampleLocationNV structures specifying the location of each sample in the custom ordering.

The `VkCoarseSampleOrderCustomNV` structure is used with a coverage sample ordering type of `VK_COARSE_SAMPLE_ORDER_TYPE_CUSTOM_NV` to specify the order of coverage samples for one combination of fragment width, fragment height, and coverage sample count.

When using a custom sample ordering, element j in `pSampleLocations` specifies a specific pixel location and sample index that corresponds to coverage index j in the multi-pixel fragment.

Valid Usage

- VUID-VkCoarseSampleOrderCustomNV-shadingRate-02073
  `shadingRate` must be a shading rate that generates fragments with more than one pixel

- VUID-VkCoarseSampleOrderCustomNV-sampleCount-02074
  `sampleCount` must correspond to a sample count enumerated in VkSampleCountFlags whose corresponding bit is set in VkPhysicalDeviceLimits::`framebufferNoAttachmentsSampleCounts`

- VUID-VkCoarseSampleOrderCustomNV-sampleLocationCount-02075
  `sampleLocationCount` must be equal to the product of `sampleCount`, the fragment width for `shadingRate`, and the fragment height for `shadingRate`

- VUID-VkCoarseSampleOrderCustomNV-sampleLocationCount-02076
  `sampleLocationCount` must be less than or equal to the value of `VkPhysicalDeviceShadingRateImagePropertiesNV`::`shadingRateMaxCoarseSamples`

- VUID-VkCoarseSampleOrderCustomNV-pSampleLocations-02077
  The array `pSampleLocations` must contain exactly one entry for every combination of valid values for `pixelX`, `pixelY`, and `sample` in the structure VkCoarseSampleOrderCustomNV

Valid Usage (Implicit)

- VUID-VkCoarseSampleOrderCustomNV-shadingRate-parameter
  `shadingRate` must be a valid VkShadingRatePaletteEntryNV value

- VUID-VkCoarseSampleOrderCustomNV-pSampleLocations-parameter
  `pSampleLocations` must be a valid pointer to an array of `sampleLocationCount` VkCoarseSampleLocationNV structures

- VUID-VkCoarseSampleOrderCustomNV-sampleLocationCount-arraylength
  `sampleLocationCount` must be greater than `0`

The `VkCoarseSampleLocationNV` structure identifies a specific pixel and sample index for one of the coverage samples in a fragment that is larger than one pixel. This structure is defined as:

    // Provided by VK_NV_shading_rate_image
    typedef struct VkCoarseSampleLocationNV {
        uint32_t    pixelX;
        uint32_t    pixelY;
        uint32_t    sample;
    } VkCoarseSampleLocationNV;

- `pixelX` is added to the x coordinate of the upper-leftmost pixel of each fragment to identify the pixel containing the coverage sample.

- `pixelY` is added to the y coordinate of the upper-leftmost pixel of each fragment to identify the pixel containing the coverage sample.

- `sample` is the number of the coverage sample in the pixel identified by `pixelX` and `pixelY`.

Valid Usage

- VUID-VkCoarseSampleLocationNV-pixelX-02078
  `pixelX` must be less than the width (in pixels) of the fragment

- VUID-VkCoarseSampleLocationNV-pixelY-02079
  `pixelY` must be less than the height (in pixels) of the fragment

- VUID-VkCoarseSampleLocationNV-sample-02080
  `sample` must be less than the number of coverage samples in each pixel belonging to the fragment

To dynamically set the order of coverage samples in fragments larger than one pixel, call:

    // Provided by VK_NV_shading_rate_image
    void vkCmdSetCoarseSampleOrderNV(
        VkCommandBuffer                             commandBuffer,
        VkCoarseSampleOrderTypeNV                   sampleOrderType,
        uint32_t                                    customSampleOrderCount,
        const VkCoarseSampleOrderCustomNV*          pCustomSampleOrders);

- `commandBuffer` is the command buffer into which the command will be recorded.

- `sampleOrderType` specifies the mechanism used to order coverage samples in fragments larger than one pixel.

- `customSampleOrderCount` specifies the number of custom sample orderings to use when ordering coverage samples.

- `pCustomSampleOrders` is a pointer to an array of VkCoarseSampleOrderCustomNV structures, each structure specifying the coverage sample order for a single combination of fragment area and coverage sample count.

If `sampleOrderType` is `VK_COARSE_SAMPLE_ORDER_TYPE_CUSTOM_NV`, the coverage sample order used for any combination of fragment area and coverage sample count not enumerated in `pCustomSampleOrders` will be identical to that used for `VK_COARSE_SAMPLE_ORDER_TYPE_DEFAULT_NV`.

This command sets the order of coverage samples for subsequent drawing commands when the graphics pipeline is created with `VK_DYNAMIC_STATE_VIEWPORT_COARSE_SAMPLE_ORDER_NV` set in VkPipelineDynamicStateCreateInfo::`pDynamicStates`. Otherwise, this state is specified by the VkPipelineViewportCoarseSampleOrderStateCreateInfoNV values used to create the currently active pipeline.

Valid Usage

- VUID-vkCmdSetCoarseSampleOrderNV-sampleOrderType-02081
  If `sampleOrderType` is not `VK_COARSE_SAMPLE_ORDER_TYPE_CUSTOM_NV`, `customSamplerOrderCount` must be `0`

- VUID-vkCmdSetCoarseSampleOrderNV-pCustomSampleOrders-02235
  The array `pCustomSampleOrders` must not contain two structures with matching values for both the `shadingRate` and `sampleCount` members

Valid Usage (Implicit)

- VUID-vkCmdSetCoarseSampleOrderNV-commandBuffer-parameter
  `commandBuffer` must be a valid VkCommandBuffer handle

- VUID-vkCmdSetCoarseSampleOrderNV-sampleOrderType-parameter
  `sampleOrderType` must be a valid VkCoarseSampleOrderTypeNV value

- VUID-vkCmdSetCoarseSampleOrderNV-pCustomSampleOrders-parameter
  If `customSampleOrderCount` is not `0`, `pCustomSampleOrders` must be a valid pointer to an array of `customSampleOrderCount` valid VkCoarseSampleOrderCustomNV structures

- VUID-vkCmdSetCoarseSampleOrderNV-commandBuffer-recording
  `commandBuffer` must be in the recording state

- VUID-vkCmdSetCoarseSampleOrderNV-commandBuffer-cmdpool
  The `VkCommandPool` that `commandBuffer` was allocated from must support graphics operations

- VUID-vkCmdSetCoarseSampleOrderNV-videocoding
  This command must only be called outside of a video coding scope

Host Synchronization

- Host access to `commandBuffer` must be externally synchronized

- Host access to the `VkCommandPool` that `commandBuffer` was allocated from must be externally synchronized

Command Properties

Command Buffer Levels | Render Pass Scope | Video Coding Scope | Supported Queue Types
--- | --- | --- | ---
Primary Secondary | Both | Outside | Graphics

If the final shading rate for a primitive covering pixel (x,y) results in n invocations per pixel (n > 1), n separate fragment shader invocations will be generated for the fragment. Each coverage sample in the fragment will be assigned to one of the n fragment shader invocations in an implementation-dependent manner. The outputs from the fragment output interface of each shader invocation will be broadcast to all of the framebuffer samples associated with the invocation. If none of the coverage samples associated with a fragment shader invocation is covered by a primitive, the implementation may discard the fragment shader invocation for those samples.

If the final shading rate for a primitive covering pixel (x,y) results in a fragment containing multiple pixels, a single set of fragment shader invocations will be generated for all pixels in the combined fragment. Outputs from the fragment output interface will be broadcast to all covered framebuffer samples belonging to the fragment. If the fragment shader executes code discarding the fragment, none of the samples of the fragment will be updated.

### 27.8. Sample Shading

Sample shading can be used to specify a minimum number of unique samples to process for each fragment. If sample shading is enabled, an implementation must invoke the fragment shader at least max(⌈ VkPipelineMultisampleStateCreateInfo::`minSampleShading` × VkPipelineMultisampleStateCreateInfo::`rasterizationSamples` ⌉, 1) times per fragment. If a fragment shader entry point’s interface includes an input variable decorated with a `BuiltIn` of `SampleId` or `SamplePosition`, a value of `1.0` is used instead of `minSampleShading`. If the `VK_AMD_mixed_attachment_samples` extension is enabled and the subpass uses color attachments, the `samples` value used to create each color attachment is used instead of `rasterizationSamples`.

Sample shading is enabled if at least one of the following conditions is true:

- VkPipelineMultisampleStateCreateInfo::`sampleShadingEnable` is set to `VK_TRUE`, or

- the fragment shader’s entry point interface includes input variables decorated with a `BuiltIn` of `SampleId` or `SamplePosition` built-ins.

If there are fewer invocations than covered samples, implementations may include those samples in fragment shader invocations in any manner as long as covered samples are all shaded at least once.

### 27.9. Barycentric Interpolation

When the `fragmentShaderBarycentric` feature is enabled, the `PerVertexKHR` interpolation decoration can be used with fragment shader inputs to indicate that the decorated inputs do not have associated data in the fragment. Such inputs can only be accessed in a fragment shader using an array index whose value (0, 1, or 2) identifies one of the vertices of the primitive that produced the fragment. Reads of per-vertex values for missing vertices, such as the third vertex of a line primitive, will return values from the valid vertex with the highest index. This means that the per-vertex values of indices 1 and 2 for point primitives will be equal to those of index 0, and the per-vertex values of index 2 for line primitives will be equal to those of index 1.

When tessellation, geometry shading, and mesh shading are not active, fragment shader inputs decorated with `PerVertexKHR` will take values from one of the vertices of the primitive that produced the fragment, identified by the extra index provided in SPIR-V code accessing the input. If the n vertices passed to a draw call are numbered 0 through n-1, and the point, line, and triangle primitives produced by the draw call are numbered with consecutive integers beginning with zero, the following table indicates the original vertex numbers used when the provoking vertex mode is `VK_PROVOKING_VERTEX_MODE_FIRST_VERTEX_EXT` for index values of 0, 1, and 2. If an input decorated with `PerVertexKHR` is accessed with any other vertex index value, or is accessed while rasterizing a polygon when the VkPipelineRasterizationStateCreateInfo::`polygonMode` property of the currently active pipeline is not `VK_POLYGON_MODE_FILL`, an undefined value is returned.

Primitive Topology | Vertex 0 | Vertex 1 | Vertex 2
--- | --- | --- | ---
`VK_PRIMITIVE_TOPOLOGY_POINT_LIST` | i | i | i
`VK_PRIMITIVE_TOPOLOGY_LINE_LIST` | 2i | 2i+1 | 2i+1
`VK_PRIMITIVE_TOPOLOGY_LINE_STRIP` | i | i+1 | i+1
`VK_PRIMITIVE_TOPOLOGY_TRIANGLE_LIST` | 3i | 3i+1 | 3i+2
`VK_PRIMITIVE_TOPOLOGY_TRIANGLE_STRIP` (even) | i | i+1 | i+2
`VK_PRIMITIVE_TOPOLOGY_TRIANGLE_STRIP` (odd) | i | i+2 | i+1
`VK_PRIMITIVE_TOPOLOGY_TRIANGLE_FAN` | i+1 | i+2 | 0
`VK_PRIMITIVE_TOPOLOGY_LINE_LIST_WITH_ADJACENCY` | 4i+1 | 4i+2 | 4i+2
`VK_PRIMITIVE_TOPOLOGY_LINE_STRIP_WITH_ADJACENCY` | i+1 | i+2 | i+2
`VK_PRIMITIVE_TOPOLOGY_TRIANGLE_LIST_WITH_ADJACENCY` | 6i | 6i+2 | 6i+4
`VK_PRIMITIVE_TOPOLOGY_TRIANGLE_STRIP_WITH_ADJACENCY` (even) | 2i | 2i+2 | 2i+4
`VK_PRIMITIVE_TOPOLOGY_TRIANGLE_STRIP_WITH_ADJACENCY` (odd) | 2i | 2i+4 | 2i+2

When the provoking vertex mode is `VK_PROVOKING_VERTEX_MODE_LAST_VERTEX_EXT`, the original vertex numbers used are the same as above except as indicated in the table below.

Primitive Topology | Vertex 0 | Vertex 1 | Vertex 2
--- | --- | --- | ---
`VK_PRIMITIVE_TOPOLOGY_TRIANGLE_STRIP` (odd, and `triStripVertexOrderIndependentOfProvokingVertex` of VkPhysicalDeviceFragmentShaderBarycentricPropertiesKHR is `VK_FALSE`) | i+1 | i | i+2
`VK_PRIMITIVE_TOPOLOGY_TRIANGLE_FAN` | 0 | i+1 | i+2
`VK_PRIMITIVE_TOPOLOGY_TRIANGLE_STRIP_WITH_ADJACENCY` (odd) | 2i+2 | 2i | 2i+4

When geometry or mesh shading is active, primitives processed by fragment shaders are assembled from the vertices emitted by the geometry or mesh shader. In this case, the vertices used for fragment shader inputs decorated with `PerVertexKHR` are derived by treating the primitives produced by the shader as though they were specified by a draw call and consulting the table above.

When using tessellation without geometry shading, the tessellator produces primitives in an implementation-dependent manner. While there is no defined vertex ordering for inputs decorated with `PerVertexKHR`, the vertex ordering used in this case will be consistent with the ordering used to derive the values of inputs decorated with `BaryCoordKHR` or `BaryCoordNoPerspKHR`.

Fragment shader inputs decorated with `BaryCoordKHR` or `BaryCoordNoPerspKHR` hold three-component vectors with barycentric weights that indicate the location of the fragment relative to the screen-space locations of vertices of its primitive. For point primitives, such variables are always assigned the value (1,0,0). For line primitives, the built-ins are obtained by interpolating an attribute whose values for the vertices numbered 0 and 1 are (1,0,0) and (0,1,0), respectively. For polygon primitives, the built-ins are obtained by interpolating an attribute whose values for the vertices numbered 0, 1, and 2 are (1,0,0), (0,1,0), and (0,0,1), respectively. For `BaryCoordKHR`, the values are obtained using perspective interpolation. For `BaryCoordNoPerspKHR`, the values are obtained using linear interpolation. The values of `BaryCoordKHR` and `BaryCoordNoPerspKHR` are undefined while rasterizing a polygon when the VkPipelineRasterizationStateCreateInfo::`polygonMode` property of the currently active pipeline is not `VK_POLYGON_MODE_FILL`.

### 27.10. Points

A point is drawn by generating a set of fragments in the shape of a square centered around the vertex of the point. Each vertex has an associated point size controlling the width/height of that square. The point size is taken from the (potentially clipped) shader built-in `PointSize` written by:

- the geometry shader, if active;

- the tessellation evaluation shader, if active and no geometry shader is active;

- the vertex shader, otherwise

and clamped to the implementation-dependent point size range [`pointSizeRange`[0],`pointSizeRange`[1]]. The value written to `PointSize` must be greater than zero.

Not all point sizes need be supported, but the size 1.0 must be supported. The range of supported sizes and the size of evenly-spaced gradations within that range are implementation-dependent. The range and gradations are obtained from the `pointSizeRange` and `pointSizeGranularity` members of VkPhysicalDeviceLimits. If, for instance, the size range is from 0.1 to 2.0 and the gradation size is 0.1, then the sizes 0.1, 0.2, …​, 1.9, 2.0 are supported. Additional point sizes may also be supported. There is no requirement that these sizes be equally spaced. If an unsupported size is requested, the nearest supported size is used instead.

Further, if the render pass has a fragment density map attachment, point size may be rounded by the implementation to a multiple of the fragment’s width or height.

#### 27.10.1. Basic Point Rasterization

Point rasterization produces a fragment for each fragment area group of framebuffer pixels with one or more sample points that intersect a region centered at the point’s (xf,yf). This region is a square with side equal to the current point size. Coverage bits that correspond to sample points that intersect the region are 1, other coverage bits are 0. All fragments produced in rasterizing a point are assigned the same associated data, which are those of the vertex corresponding to the point. However, the fragment shader built-in `PointCoord` contains point sprite texture coordinates. The s and t point sprite texture coordinates vary from zero to one across the point horizontally left-to-right and vertically top-to-bottom, respectively. The following formulas are used to evaluate s and t:

s=2 1​+size(x p​−x f​)​
t=2 1​+size(y p​−y f​)​

where size is the point’s size; (xp,yp) is the location at which the point sprite coordinates are evaluated - this may be the framebuffer coordinates of the fragment center, or the location of a sample; and (xf,yf) is the exact, unrounded framebuffer coordinate of the vertex for the point.

### 27.11. Line Segments

Line segment rasterization options are controlled by the VkPipelineRasterizationLineStateCreateInfoEXT structure.

The `VkPipelineRasterizationLineStateCreateInfoEXT` structure is defined as:

    // Provided by VK_EXT_line_rasterization
    typedef struct VkPipelineRasterizationLineStateCreateInfoEXT {
        VkStructureType               sType;
        const void*                   pNext;
        VkLineRasterizationModeEXT    lineRasterizationMode;
        VkBool32                      stippledLineEnable;
        uint32_t                      lineStippleFactor;
        uint16_t                      lineStipplePattern;
    } VkPipelineRasterizationLineStateCreateInfoEXT;

- `sType` is the type of this structure.

- `pNext` is `NULL` or a pointer to a structure extending this structure.

- `lineRasterizationMode` is a VkLineRasterizationModeEXT value selecting the style of line rasterization.

- `stippledLineEnable` enables stippled line rasterization.

- `lineStippleFactor` is the repeat factor used in stippled line rasterization.

- `lineStipplePattern` is the bit pattern used in stippled line rasterization.

If `stippledLineEnable` is `VK_FALSE`, the values of `lineStippleFactor` and `lineStipplePattern` are ignored.

Valid Usage

- VUID-VkPipelineRasterizationLineStateCreateInfoEXT-lineRasterizationMode-02768
  If `lineRasterizationMode` is `VK_LINE_RASTERIZATION_MODE_RECTANGULAR_EXT`, then the `rectangularLines` feature must be enabled

- VUID-VkPipelineRasterizationLineStateCreateInfoEXT-lineRasterizationMode-02769
  If `lineRasterizationMode` is `VK_LINE_RASTERIZATION_MODE_BRESENHAM_EXT`, then the `bresenhamLines` feature must be enabled

- VUID-VkPipelineRasterizationLineStateCreateInfoEXT-lineRasterizationMode-02770
  If `lineRasterizationMode` is `VK_LINE_RASTERIZATION_MODE_RECTANGULAR_SMOOTH_EXT`, then the `smoothLines` feature must be enabled

- VUID-VkPipelineRasterizationLineStateCreateInfoEXT-stippledLineEnable-02771
  If `stippledLineEnable` is `VK_TRUE` and `lineRasterizationMode` is `VK_LINE_RASTERIZATION_MODE_RECTANGULAR_EXT`, then the `stippledRectangularLines` feature must be enabled

- VUID-VkPipelineRasterizationLineStateCreateInfoEXT-stippledLineEnable-02772
  If `stippledLineEnable` is `VK_TRUE` and `lineRasterizationMode` is `VK_LINE_RASTERIZATION_MODE_BRESENHAM_EXT`, then the `stippledBresenhamLines` feature must be enabled

- VUID-VkPipelineRasterizationLineStateCreateInfoEXT-stippledLineEnable-02773
  If `stippledLineEnable` is `VK_TRUE` and `lineRasterizationMode` is `VK_LINE_RASTERIZATION_MODE_RECTANGULAR_SMOOTH_EXT`, then the `stippledSmoothLines` feature must be enabled

- VUID-VkPipelineRasterizationLineStateCreateInfoEXT-stippledLineEnable-02774
  If `stippledLineEnable` is `VK_TRUE` and `lineRasterizationMode` is `VK_LINE_RASTERIZATION_MODE_DEFAULT_EXT`, then the `stippledRectangularLines` feature must be enabled and VkPhysicalDeviceLimits::`strictLines` must be `VK_TRUE`

Valid Usage (Implicit)

- VUID-VkPipelineRasterizationLineStateCreateInfoEXT-sType-sType
  `sType` must be `VK_STRUCTURE_TYPE_PIPELINE_RASTERIZATION_LINE_STATE_CREATE_INFO_EXT`

- VUID-VkPipelineRasterizationLineStateCreateInfoEXT-lineRasterizationMode-parameter
  `lineRasterizationMode` must be a valid VkLineRasterizationModeEXT value

Possible values of VkPipelineRasterizationLineStateCreateInfoEXT::`lineRasterizationMode` are:

    // Provided by VK_EXT_line_rasterization
    typedef enum VkLineRasterizationModeEXT {
        VK_LINE_RASTERIZATION_MODE_DEFAULT_EXT = 0,
        VK_LINE_RASTERIZATION_MODE_RECTANGULAR_EXT = 1,
        VK_LINE_RASTERIZATION_MODE_BRESENHAM_EXT = 2,
        VK_LINE_RASTERIZATION_MODE_RECTANGULAR_SMOOTH_EXT = 3,
    } VkLineRasterizationModeEXT;

- `VK_LINE_RASTERIZATION_MODE_DEFAULT_EXT` is equivalent to `VK_LINE_RASTERIZATION_MODE_RECTANGULAR_EXT` if VkPhysicalDeviceLimits::`strictLines` is `VK_TRUE`, otherwise lines are drawn as non-`strictLines` parallelograms. Both of these modes are defined in Basic Line Segment Rasterization.

- `VK_LINE_RASTERIZATION_MODE_RECTANGULAR_EXT` specifies lines drawn as if they were rectangles extruded from the line

- `VK_LINE_RASTERIZATION_MODE_BRESENHAM_EXT` specifies lines drawn by determining which pixel diamonds the line intersects and exits, as defined in Bresenham Line Segment Rasterization.

- `VK_LINE_RASTERIZATION_MODE_RECTANGULAR_SMOOTH_EXT` specifies lines drawn if they were rectangles extruded from the line, with alpha falloff, as defined in Smooth Lines.

To dynamically set the line width, call:

    // Provided by VK_VERSION_1_0
    void vkCmdSetLineWidth(
        VkCommandBuffer                             commandBuffer,
        float                                       lineWidth);

- `commandBuffer` is the command buffer into which the command will be recorded.

- `lineWidth` is the width of rasterized line segments.

This command sets the line width for subsequent drawing commands when the graphics pipeline is created with `VK_DYNAMIC_STATE_LINE_WIDTH` set in VkPipelineDynamicStateCreateInfo::`pDynamicStates`. Otherwise, this state is specified by the VkPipelineRasterizationStateCreateInfo::`lineWidth` value used to create the currently active pipeline.

Valid Usage

- VUID-vkCmdSetLineWidth-lineWidth-00788
  If the `wideLines` feature is not enabled, `lineWidth` must be `1.0`

Valid Usage (Implicit)

- VUID-vkCmdSetLineWidth-commandBuffer-parameter
  `commandBuffer` must be a valid VkCommandBuffer handle

- VUID-vkCmdSetLineWidth-commandBuffer-recording
  `commandBuffer` must be in the recording state

- VUID-vkCmdSetLineWidth-commandBuffer-cmdpool
  The `VkCommandPool` that `commandBuffer` was allocated from must support graphics operations

- VUID-vkCmdSetLineWidth-videocoding
  This command must only be called outside of a video coding scope

Host Synchronization

- Host access to `commandBuffer` must be externally synchronized

- Host access to the `VkCommandPool` that `commandBuffer` was allocated from must be externally synchronized

Command Properties

Command Buffer Levels | Render Pass Scope | Video Coding Scope | Supported Queue Types
--- | --- | --- | ---
Primary Secondary | Both | Outside | Graphics

Not all line widths need be supported for line segment rasterization, but width 1.0 antialiased segments must be provided. The range and gradations are obtained from the `lineWidthRange` and `lineWidthGranularity` members of VkPhysicalDeviceLimits. If, for instance, the size range is from 0.1 to 2.0 and the gradation size is 0.1, then the sizes 0.1, 0.2, …​, 1.9, 2.0 are supported. Additional line widths may also be supported. There is no requirement that these widths be equally spaced. If an unsupported width is requested, the nearest supported width is used instead.

Further, if the render pass has a fragment density map attachment, line width may be rounded by the implementation to a multiple of the fragment’s width or height.

#### 27.11.1. Basic Line Segment Rasterization

If the `lineRasterizationMode` member of VkPipelineRasterizationLineStateCreateInfoEXT is `VK_LINE_RASTERIZATION_MODE_RECTANGULAR_EXT`, rasterized line segments produce fragments which intersect a rectangle centered on the line segment. Two of the edges are parallel to the specified line segment; each is at a distance of one-half the current width from that segment in directions perpendicular to the direction of the line. The other two edges pass through the line endpoints and are perpendicular to the direction of the specified line segment. Coverage bits that correspond to sample points that intersect the rectangle are 1, other coverage bits are 0.

Next we specify how the data associated with each rasterized fragment are obtained. Let pr = (xd, yd) be the framebuffer coordinates at which associated data are evaluated. This may be the center of a fragment or the location of a sample within the fragment. When `rasterizationSamples` is `VK_SAMPLE_COUNT_1_BIT`, the fragment center must be used. Let pa = (xa, ya) and pb = (xb,yb) be initial and final endpoints of the line segment, respectively. Set

t=∥p b​−p a​∥2(p r​−p a​)⋅(p b​−p a​)​

(Note that t = 0 at pa and t = 1 at pb. Also note that this calculation projects the vector from pa to pr onto the line, and thus computes the normalized distance of the fragment along the line.)

If `strictLines` is `VK_TRUE`, line segments are rasterized using perspective or linear interpolation.

Perspective interpolation for a line segment interpolates two values in a manner that is correct when taking the perspective of the viewport into consideration, by way of the line segment’s clip coordinates. An interpolated value f can be determined by

f=(1−t)/w a​+t/w b​(1−t)f a​/w a​+t f b​/w b​​

where fa and fb are the data associated with the starting and ending endpoints of the segment, respectively; wa and wb are the clip w coordinates of the starting and ending endpoints of the segment, respectively.

Linear interpolation for a line segment directly interpolates two values, and an interpolated value f can be determined by

  f = (1 - t) fa + t fb

where fa and fb are the data associated with the starting and ending endpoints of the segment, respectively.

The clip coordinate w for a sample is determined using perspective interpolation. The depth value z for a sample is determined using linear interpolation. Interpolation of fragment shader input values are determined by Interpolation decorations.

The above description documents the preferred method of line rasterization, and must be used when `lineRasterizationMode` is `VK_LINE_RASTERIZATION_MODE_RECTANGULAR_EXT`.

When `strictLines` is `VK_FALSE`, and when the `lineRasterizationMode` is `VK_LINE_RASTERIZATION_MODE_DEFAULT_EXT`, the edges of the lines are generated as a parallelogram surrounding the original line. The major axis is chosen by noting the axis in which there is the greatest distance between the line start and end points. If the difference is equal in both directions then the X axis is chosen as the major axis. Edges 2 and 3 are aligned to the minor axis and are centered on the endpoints of the line as in Non strict lines, and each is `lineWidth` long. Edges 0 and 1 are parallel to the line and connect the endpoints of edges 2 and 3. Coverage bits that correspond to sample points that intersect the parallelogram are 1, other coverage bits are 0.

Samples that fall exactly on the edge of the parallelogram follow the polygon rasterization rules.

Interpolation occurs as if the parallelogram was decomposed into two triangles where each pair of vertices at each end of the line has identical attributes.

Figure 20. Non strict lines

Only when `strictLines` is `VK_FALSE` implementations may deviate from the non-strict line algorithm described above in the following ways:

- Implementations may instead interpolate each fragment according to the formula in Basic Line Segment Rasterization using the original line segment endpoints.

- Rasterization of non-antialiased non-strict line segments may be performed using the rules defined in Bresenham Line Segment Rasterization.

#### 27.11.2. Bresenham Line Segment Rasterization

If `lineRasterizationMode` is `VK_LINE_RASTERIZATION_MODE_BRESENHAM_EXT`, then the following rules replace the line rasterization rules defined in Basic Line Segment Rasterization.

Non-strict lines may also follow these rasterization rules for non-antialiased lines.

Line segment rasterization begins by characterizing the segment as either x-major or y-major. x-major line segments have slope in the closed interval [-1,1]; all other line segments are y-major (slope is determined by the segment’s endpoints). We specify rasterization only for x-major segments except in cases where the modifications for y-major segments are not self-evident.

Ideally, Vulkan uses a diamond-exit rule to determine those fragments that are produced by rasterizing a line segment. For each fragment f with center at framebuffer coordinates xf and yf, define a diamond-shaped region that is the intersection of four half planes:

R f​={(x, y)∣∣x−x f​∣+∣y−y f​∣<2 1​}

Essentially, a line segment starting at pa and ending at pb produces those fragments f for which the segment intersects Rf, except if pb is contained in Rf.

Figure 21. Visualization of Bresenham’s algorithm

To avoid difficulties when an endpoint lies on a boundary of Rf we (in principle) perturb the supplied endpoints by a tiny amount. Let pa and pb have framebuffer coordinates (xa, ya) and (xb, yb), respectively. Obtain the perturbed endpoints pa' given by (xa, ya) - (ε, ε2) and pb' given by (xb, yb) - (ε, ε2). Rasterizing the line segment starting at pa and ending at pb produces those fragments f for which the segment starting at pa' and ending on pb' intersects Rf, except if pb' is contained in Rf. ε is chosen to be so small that rasterizing the line segment produces the same fragments when δ is substituted for ε for any 0 < δ ≤ ε.

When pa and pb lie on fragment centers, this characterization of fragments reduces to Bresenham’s algorithm with one modification: lines produced in this description are “half-open”, meaning that the final fragment (corresponding to pb) is not drawn. This means that when rasterizing a series of connected line segments, shared endpoints will be produced only once rather than twice (as would occur with Bresenham’s algorithm).

Implementations may use other line segment rasterization algorithms, subject to the following rules:

- The coordinates of a fragment produced by the algorithm must not deviate by more than one unit in either x or y framebuffer coordinates from a corresponding fragment produced by the diamond-exit rule.

- The total number of fragments produced by the algorithm must not differ from that produced by the diamond-exit rule by no more than one.

- For an x-major line, two fragments that lie in the same framebuffer-coordinate column must not be produced (for a y-major line, two fragments that lie in the same framebuffer-coordinate row must not be produced).

- If two line segments share a common endpoint, and both segments are either x-major (both left-to-right or both right-to-left) or y-major (both bottom-to-top or both top-to-bottom), then rasterizing both segments must not produce duplicate fragments. Fragments also must not be omitted so as to interrupt continuity of the connected segments.

The actual width w of Bresenham lines is determined by rounding the line width to the nearest integer, clamping it to the implementation-dependent `lineWidthRange` (with both values rounded to the nearest integer), then clamping it to be no less than 1.

Bresenham line segments of width other than one are rasterized by offsetting them in the minor direction (for an x-major line, the minor direction is y, and for a y-major line, the minor direction is x) and producing a row or column of fragments in the minor direction. If the line segment has endpoints given by (x0, y0) and (x1, y1) in framebuffer coordinates, the segment with endpoints (x 0​,y 0​−2 w−1​) and (x 1​,y 1​−2 w−1​) is rasterized, but instead of a single fragment, a column of fragments of height w (a row of fragments of length w for a y-major segment) is produced at each x (y for y-major) location. The lowest fragment of this column is the fragment that would be produced by rasterizing the segment of width 1 with the modified coordinates.

The preferred method of attribute interpolation for a wide line is to generate the same attribute values for all fragments in the row or column described above, as if the adjusted line was used for interpolation and those values replicated to the other fragments, except for `FragCoord` which is interpolated as usual. Implementations may instead interpolate each fragment according to the formula in Basic Line Segment Rasterization, using the original line segment endpoints.

When Bresenham lines are being rasterized, sample locations may all be treated as being at the pixel center (this may affect attribute and depth interpolation).

| Note The sample locations described above are not used for determining coverage, they are only used for things like attribute interpolation. The rasterization rules that determine coverage are defined in terms of whether the line intersects pixels, as opposed to the point sampling rules used for other primitive types. So these rules are independent of the sample locations. One consequence of this is that Bresenham lines cover the same pixels regardless of the number of rasterization samples, and cover all samples in those pixels (unless masked out or killed).

#### 27.11.3. Line Stipple

If the `stippledLineEnable` member of VkPipelineRasterizationLineStateCreateInfoEXT is `VK_TRUE`, then lines are rasterized with a line stipple determined by `lineStippleFactor` and `lineStipplePattern`. `lineStipplePattern` is an unsigned 16-bit integer that determines which fragments are to be drawn or discarded when the line is rasterized. `lineStippleFactor` is a count that is used to modify the effective line stipple by causing each bit in `lineStipplePattern` to be used `lineStippleFactor` times.

Line stippling discards certain fragments that are produced by rasterization. The masking is achieved using three parameters: the 16-bit line stipple pattern p, the line stipple factor r, and an integer stipple counter s. Let

b=⌊r s​⌋mod 16

Then a fragment is produced if the b'th bit of p is 1, and discarded otherwise. The bits of p are numbered with 0 being the least significant and 15 being the most significant.

The initial value of s is zero. For `VK_LINE_RASTERIZATION_MODE_BRESENHAM_EXT` lines, s is incremented after production of each fragment of a line segment (fragments are produced in order, beginning at the starting point and working towards the ending point). For `VK_LINE_RASTERIZATION_MODE_RECTANGULAR_EXT` and `VK_LINE_RASTERIZATION_MODE_RECTANGULAR_SMOOTH_EXT` lines, the rectangular region is subdivided into adjacent unit-length rectangles, and s is incremented once for each rectangle. Rectangles with a value of s such that the b'th bit of p is zero are discarded. If the last rectangle in a line segment is shorter than unit-length, then the remainder may carry over to the next line segment in the line strip using the same value of s (this is the preferred behavior, for the stipple pattern to appear more consistent through the strip).

s is reset to 0 at the start of each strip (for line strips), and before every line segment in a group of independent segments.

If the line segment has been clipped, then the value of s at the beginning of the line segment is implementation-dependent.

To dynamically set the line stipple state, call:

    // Provided by VK_EXT_line_rasterization
    void vkCmdSetLineStippleEXT(
        VkCommandBuffer                             commandBuffer,
        uint32_t                                    lineStippleFactor,
        uint16_t                                    lineStipplePattern);

- `commandBuffer` is the command buffer into which the command will be recorded.

- `lineStippleFactor` is the repeat factor used in stippled line rasterization.

- `lineStipplePattern` is the bit pattern used in stippled line rasterization.

This command sets the line stipple state for subsequent drawing commands when the graphics pipeline is created with `VK_DYNAMIC_STATE_LINE_STIPPLE_EXT` set in VkPipelineDynamicStateCreateInfo::`pDynamicStates`. Otherwise, this state is specified by the VkPipelineRasterizationLineStateCreateInfoEXT::`lineStippleFactor` and VkPipelineRasterizationLineStateCreateInfoEXT::`lineStipplePattern` values used to create the currently active pipeline.

Valid Usage

- VUID-vkCmdSetLineStippleEXT-lineStippleFactor-02776
  `lineStippleFactor` must be in the range [1,256]

Valid Usage (Implicit)

- VUID-vkCmdSetLineStippleEXT-commandBuffer-parameter
  `commandBuffer` must be a valid VkCommandBuffer handle

- VUID-vkCmdSetLineStippleEXT-commandBuffer-recording
  `commandBuffer` must be in the recording state

- VUID-vkCmdSetLineStippleEXT-commandBuffer-cmdpool
  The `VkCommandPool` that `commandBuffer` was allocated from must support graphics operations

- VUID-vkCmdSetLineStippleEXT-videocoding
  This command must only be called outside of a video coding scope

Host Synchronization

- Host access to `commandBuffer` must be externally synchronized

- Host access to the `VkCommandPool` that `commandBuffer` was allocated from must be externally synchronized

Command Properties

Command Buffer Levels | Render Pass Scope | Video Coding Scope | Supported Queue Types
--- | --- | --- | ---
Primary Secondary | Both | Outside | Graphics

#### 27.11.4. Smooth Lines

If the `lineRasterizationMode` member of VkPipelineRasterizationLineStateCreateInfoEXT is `VK_LINE_RASTERIZATION_MODE_RECTANGULAR_SMOOTH_EXT`, then lines are considered to be rectangles using the same geometry as for `VK_LINE_RASTERIZATION_MODE_RECTANGULAR_EXT` lines. The rules for determining which pixels are covered are implementation-dependent, and may include nearby pixels where no sample locations are covered or where the rectangle does not intersect the pixel at all. For each pixel that is considered covered, the fragment computes a coverage value that approximates the area of the intersection of the rectangle with the pixel square, and this coverage value is multiplied into the color location 0’s alpha value after fragment shading, as described in Multisample Coverage.

| Note The details of the rasterization rules and area calculation are left intentionally vague, to allow implementations to generate coverage and values that are aesthetically pleasing.

### 27.12. Polygons

A polygon results from the decomposition of a triangle strip, triangle fan or a series of independent triangles. Like points and line segments, polygon rasterization is controlled by several variables in the VkPipelineRasterizationStateCreateInfo structure.

#### 27.12.1. Basic Polygon Rasterization

The first step of polygon rasterization is to determine whether the triangle is back-facing or front-facing. This determination is made based on the sign of the (clipped or unclipped) polygon’s area computed in framebuffer coordinates. One way to compute this area is:

a=−2 1​i=0∑n−1​x f i​y f i⊕1​−x f i⊕1​y f i​

where x f i​ and y f i​ are the x and y framebuffer coordinates of the ith vertex of the n-vertex polygon (vertices are numbered starting at zero for the purposes of this computation) and i ⊕ 1 is (i + 1) mod n.

The interpretation of the sign of a is determined by the VkPipelineRasterizationStateCreateInfo::`frontFace` property of the currently active pipeline. Possible values are:

    // Provided by VK_VERSION_1_0
    typedef enum VkFrontFace {
        VK_FRONT_FACE_COUNTER_CLOCKWISE = 0,
        VK_FRONT_FACE_CLOCKWISE = 1,
    } VkFrontFace;

- `VK_FRONT_FACE_COUNTER_CLOCKWISE` specifies that a triangle with positive area is considered front-facing.

- `VK_FRONT_FACE_CLOCKWISE` specifies that a triangle with negative area is considered front-facing.

Any triangle which is not front-facing is back-facing, including zero-area triangles.

To dynamically set the front face orientation, call:

    // Provided by VK_VERSION_1_3
    void vkCmdSetFrontFace(
        VkCommandBuffer                             commandBuffer,
        VkFrontFace                                 frontFace);

or the equivalent command

    // Provided by VK_EXT_extended_dynamic_state
    void vkCmdSetFrontFaceEXT(
        VkCommandBuffer                             commandBuffer,
        VkFrontFace                                 frontFace);

- `commandBuffer` is the command buffer into which the command will be recorded.

- `frontFace` is a VkFrontFace value specifying the front-facing triangle orientation to be used for culling.

This command sets the front face orientation for subsequent drawing commands when the graphics pipeline is created with `VK_DYNAMIC_STATE_FRONT_FACE` set in VkPipelineDynamicStateCreateInfo::`pDynamicStates`. Otherwise, this state is specified by the VkPipelineRasterizationStateCreateInfo::`frontFace` value used to create the currently active pipeline.

Valid Usage (Implicit)

- VUID-vkCmdSetFrontFace-commandBuffer-parameter
  `commandBuffer` must be a valid VkCommandBuffer handle

- VUID-vkCmdSetFrontFace-frontFace-parameter
  `frontFace` must be a valid VkFrontFace value

- VUID-vkCmdSetFrontFace-commandBuffer-recording
  `commandBuffer` must be in the recording state

- VUID-vkCmdSetFrontFace-commandBuffer-cmdpool
  The `VkCommandPool` that `commandBuffer` was allocated from must support graphics operations

- VUID-vkCmdSetFrontFace-videocoding
  This command must only be called outside of a video coding scope

Host Synchronization

- Host access to `commandBuffer` must be externally synchronized

- Host access to the `VkCommandPool` that `commandBuffer` was allocated from must be externally synchronized

Command Properties

Command Buffer Levels | Render Pass Scope | Video Coding Scope | Supported Queue Types
--- | --- | --- | ---
Primary Secondary | Both | Outside | Graphics

Once the orientation of triangles is determined, they are culled according to the VkPipelineRasterizationStateCreateInfo::`cullMode` property of the currently active pipeline. Possible values are:

    // Provided by VK_VERSION_1_0
    typedef enum VkCullModeFlagBits {
        VK_CULL_MODE_NONE = 0,
        VK_CULL_MODE_FRONT_BIT = 0x00000001,
        VK_CULL_MODE_BACK_BIT = 0x00000002,
        VK_CULL_MODE_FRONT_AND_BACK = 0x00000003,
    } VkCullModeFlagBits;

- `VK_CULL_MODE_NONE` specifies that no triangles are discarded

- `VK_CULL_MODE_FRONT_BIT` specifies that front-facing triangles are discarded

- `VK_CULL_MODE_BACK_BIT` specifies that back-facing triangles are discarded

- `VK_CULL_MODE_FRONT_AND_BACK` specifies that all triangles are discarded.

Following culling, fragments are produced for any triangles which have not been discarded.

    // Provided by VK_VERSION_1_0
    typedef VkFlags VkCullModeFlags;

`VkCullModeFlags` is a bitmask type for setting a mask of zero or more VkCullModeFlagBits.

To dynamically set the cull mode, call:

    // Provided by VK_VERSION_1_3
    void vkCmdSetCullMode(
        VkCommandBuffer                             commandBuffer,
        VkCullModeFlags                             cullMode);

or the equivalent command

    // Provided by VK_EXT_extended_dynamic_state
    void vkCmdSetCullModeEXT(
        VkCommandBuffer                             commandBuffer,
        VkCullModeFlags                             cullMode);

- `commandBuffer` is the command buffer into which the command will be recorded.

- `cullMode` specifies the cull mode property to use for drawing.

This command sets the cull mode for subsequent drawing commands when the graphics pipeline is created with `VK_DYNAMIC_STATE_CULL_MODE` set in VkPipelineDynamicStateCreateInfo::`pDynamicStates`. Otherwise, this state is specified by the VkPipelineRasterizationStateCreateInfo::`cullMode` value used to create the currently active pipeline.

Valid Usage (Implicit)

- VUID-vkCmdSetCullMode-commandBuffer-parameter
  `commandBuffer` must be a valid VkCommandBuffer handle

- VUID-vkCmdSetCullMode-cullMode-parameter
  `cullMode` must be a valid combination of VkCullModeFlagBits values

- VUID-vkCmdSetCullMode-commandBuffer-recording
  `commandBuffer` must be in the recording state

- VUID-vkCmdSetCullMode-commandBuffer-cmdpool
  The `VkCommandPool` that `commandBuffer` was allocated from must support graphics operations

- VUID-vkCmdSetCullMode-videocoding
  This command must only be called outside of a video coding scope

Host Synchronization

- Host access to `commandBuffer` must be externally synchronized

- Host access to the `VkCommandPool` that `commandBuffer` was allocated from must be externally synchronized

Command Properties

Command Buffer Levels | Render Pass Scope | Video Coding Scope | Supported Queue Types
--- | --- | --- | ---
Primary Secondary | Both | Outside | Graphics

The rule for determining which fragments are produced by polygon rasterization is called point sampling. The two-dimensional projection obtained by taking the x and y framebuffer coordinates of the polygon’s vertices is formed. Fragments are produced for any fragment area groups of pixels for which any sample points lie inside of this polygon. Coverage bits that correspond to sample points that satisfy the point sampling criteria are 1, other coverage bits are 0. Special treatment is given to a sample whose sample location lies on a polygon edge. In such a case, if two polygons lie on either side of a common edge (with identical endpoints) on which a sample point lies, then exactly one of the polygons must result in a covered sample for that fragment during rasterization. As for the data associated with each fragment produced by rasterizing a polygon, we begin by specifying how these values are produced for fragments in a triangle.

Barycentric coordinates are a set of three numbers, a, b, and c, each in the range [0,1], with a + b + c = 1. These coordinates uniquely specify any point p within the triangle or on the triangle’s boundary as

  p = a pa + b pb + c pc

where pa, pb, and pc are the vertices of the triangle. a, b, and c are determined by:

a=A(p a​p b​p c​)A(pp b​p c​)​,b=A(p a​p b​p c​)A(pp a​p c​)​,c=A(p a​p b​p c​)A(pp a​p b​)​,

where A(lmn) denotes the area in framebuffer coordinates of the triangle with vertices l, m, and n.

Denote an associated datum at pa, pb, or pc as fa, fb, or fc, respectively.

Perspective interpolation for a triangle interpolates three values in a manner that is correct when taking the perspective of the viewport into consideration, by way of the triangle’s clip coordinates. An interpolated value f can be determined by

f=a/w a​+b/w b​+c/w c​a f a​/w a​+b f b​/w b​+c f c​/w c​​

where wa, wb, and wc are the clip w coordinates of pa, pb, and pc, respectively. a, b, and c are the barycentric coordinates of the location at which the data are produced.

Linear interpolation for a triangle directly interpolates three values, and an interpolated value f can be determined by

  f = a fa + b fb + c fc

where fa, fb, and fc are the data associated with pa, pb, and pc, respectively.

The clip coordinate w for a sample is determined using perspective interpolation. The depth value z for a sample is determined using linear interpolation. Interpolation of fragment shader input values are determined by Interpolation decorations.

For a polygon with more than three edges, such as are produced by clipping a triangle, a convex combination of the values of the datum at the polygon’s vertices must be used to obtain the value assigned to each fragment produced by the rasterization algorithm. That is, it must be the case that at every fragment

f=i=1∑n​a i​f i​

where n is the number of vertices in the polygon and fi is the value of f at vertex i. For each i, 0 ≤ ai ≤ 1 and ∑i=1 n​a i​=1. The values of ai may differ from fragment to fragment, but at vertex i, ai = 1 and aj = 0 for j ≠ i.

| Note One algorithm that achieves the required behavior is to triangulate a polygon (without adding any vertices) and then treat each triangle individually as already discussed. A scan-line rasterizer that linearly interpolates data along each edge and then linearly interpolates data across each horizontal span from edge to edge also satisfies the restrictions (in this case the numerator and denominator of perspective interpolation are iterated independently, and a division is performed for each fragment).

#### 27.12.2. Polygon Mode

Possible values of the VkPipelineRasterizationStateCreateInfo::`polygonMode` property of the currently active pipeline, specifying the method of rasterization for polygons, are:

    // Provided by VK_VERSION_1_0
    typedef enum VkPolygonMode {
        VK_POLYGON_MODE_FILL = 0,
        VK_POLYGON_MODE_LINE = 1,
        VK_POLYGON_MODE_POINT = 2,
      // Provided by VK_NV_fill_rectangle
        VK_POLYGON_MODE_FILL_RECTANGLE_NV = 1000153000,
    } VkPolygonMode;

- `VK_POLYGON_MODE_POINT` specifies that polygon vertices are drawn as points.

- `VK_POLYGON_MODE_LINE` specifies that polygon edges are drawn as line segments.

- `VK_POLYGON_MODE_FILL` specifies that polygons are rendered using the polygon rasterization rules in this section.

- `VK_POLYGON_MODE_FILL_RECTANGLE_NV` specifies that polygons are rendered using polygon rasterization rules, modified to consider a sample within the primitive if the sample location is inside the axis-aligned bounding box of the triangle after projection. Note that the barycentric weights used in attribute interpolation can extend outside the range [0,1] when these primitives are shaded. Special treatment is given to a sample position on the boundary edge of the bounding box. In such a case, if two rectangles lie on either side of a common edge (with identical endpoints) on which a sample position lies, then exactly one of the triangles must produce a fragment that covers that sample during rasterization.

  Polygons rendered in `VK_POLYGON_MODE_FILL_RECTANGLE_NV` mode may be clipped by the frustum or by user clip planes. If clipping is applied, the triangle is culled rather than clipped.

  Area calculation and facingness are determined for `VK_POLYGON_MODE_FILL_RECTANGLE_NV` mode using the triangle’s vertices.

These modes affect only the final rasterization of polygons: in particular, a polygon’s vertices are shaded and the polygon is clipped and possibly culled before these modes are applied.

#### 27.12.3. Depth Bias

The depth values of all fragments generated by the rasterization of a polygon can be biased (offset) by a single depth bias value o that is computed for that polygon.

##### Depth Bias Enable

The depth bias computation is enabled by the `depthBiasEnable` set with vkCmdSetDepthBiasEnable and `vkCmdSetDepthBiasEnableEXT`, or the corresponding VkPipelineRasterizationStateCreateInfo::`depthBiasEnable` value used to create the currently active pipeline. If the depth bias enable is `VK_FALSE`, no bias is applied and the fragment’s depth values are unchanged.

To dynamically enable whether to bias fragment depth values, call:

    // Provided by VK_VERSION_1_3
    void vkCmdSetDepthBiasEnable(
        VkCommandBuffer                             commandBuffer,
        VkBool32                                    depthBiasEnable);

or the equivalent command

    // Provided by VK_EXT_extended_dynamic_state2
    void vkCmdSetDepthBiasEnableEXT(
        VkCommandBuffer                             commandBuffer,
        VkBool32                                    depthBiasEnable);

- `commandBuffer` is the command buffer into which the command will be recorded.

- `depthBiasEnable` controls whether to bias fragment depth values.

This command sets the depth bias enable for subsequent drawing commands when the graphics pipeline is created with `VK_DYNAMIC_STATE_DEPTH_BIAS_ENABLE` set in VkPipelineDynamicStateCreateInfo::`pDynamicStates`. Otherwise, this state is specified by the VkPipelineRasterizationStateCreateInfo::`depthBiasEnable` value used to create the currently active pipeline.

Valid Usage (Implicit)

- VUID-vkCmdSetDepthBiasEnable-commandBuffer-parameter
  `commandBuffer` must be a valid VkCommandBuffer handle

- VUID-vkCmdSetDepthBiasEnable-commandBuffer-recording
  `commandBuffer` must be in the recording state

- VUID-vkCmdSetDepthBiasEnable-commandBuffer-cmdpool
  The `VkCommandPool` that `commandBuffer` was allocated from must support graphics operations

- VUID-vkCmdSetDepthBiasEnable-videocoding
  This command must only be called outside of a video coding scope

Host Synchronization

- Host access to `commandBuffer` must be externally synchronized

- Host access to the `VkCommandPool` that `commandBuffer` was allocated from must be externally synchronized

Command Properties

Command Buffer Levels | Render Pass Scope | Video Coding Scope | Supported Queue Types
--- | --- | --- | ---
Primary Secondary | Both | Outside | Graphics

##### Depth Bias Computation

The depth bias depends on three parameters:

- `depthBiasSlopeFactor` scales the maximum depth slope m of the polygon

- `depthBiasConstantFactor` scales the minimum resolvable difference r of the depth attachment

- the scaled terms are summed to produce a value which is then clamped to a minimum or maximum value specified by `depthBiasClamp`

`depthBiasSlopeFactor`, `depthBiasConstantFactor`, and `depthBiasClamp` can each be positive, negative, or zero. These parameters are set as described for vkCmdSetDepthBias below.

The maximum depth slope m of a triangle is

m=(∂x f​∂z f​​)2+(∂y f​∂z f​​)2
​

where (xf, yf, zf) is a point on the triangle. m may be approximated as

m=max(∣∣∣∣∣​∂x f​∂z f​​∣∣∣∣∣​,∣∣∣∣∣​∂y f​∂z f​​∣∣∣∣∣​).

The minimum resolvable difference r is a parameter that depends on the depth attachment representation. It is the smallest difference in framebuffer coordinate z values that is guaranteed to remain distinct throughout polygon rasterization and in the depth attachment. All pairs of fragments generated by the rasterization of two polygons with otherwise identical vertices, but `z`f values that differ by r, will have distinct depth values.

For fixed-point depth attachment representations, r is constant throughout the range of the entire depth attachment. Its value is implementation-dependent but must be at most

  r = 2 × 2-n

for an n-bit buffer. For floating-point depth attachment, there is no single minimum resolvable difference. In this case, the minimum resolvable difference for a given polygon is dependent on the maximum exponent, e, in the range of z values spanned by the primitive. If n is the number of bits in the floating-point mantissa, the minimum resolvable difference, r, for the given primitive is defined as

  r = 2e-n

If a triangle is rasterized using the `VK_POLYGON_MODE_FILL_RECTANGLE_NV` polygon mode, then this minimum resolvable difference may not be resolvable for samples outside of the triangle, where the depth is extrapolated.

If no depth attachment is present, r is undefined.

The bias value o for a polygon is

o where​=dbclamp(m×depthBiasSlopeFactor+r×depthBiasConstantFactor)dbclamp(x)=⎩⎪⎪⎨⎪⎪⎧​x min(x, depthBiasClamp)max(x, depthBiasClamp)​depthBiasClamp=0 or NaN depthBiasClamp>0 depthBiasClamp<0​​

m is computed as described above. If the depth attachment uses a fixed-point representation, m is a function of depth values in the range [0,1], and o is applied to depth values in the same range.

Depth bias is applied to triangle topology primitives received by the rasterizer regardless of polygon mode. Depth bias may also be applied to line and point topology primitives received by the rasterizer.

To dynamically set the depth bias parameters, call:

    // Provided by VK_VERSION_1_0
    void vkCmdSetDepthBias(
        VkCommandBuffer                             commandBuffer,
        float                                       depthBiasConstantFactor,
        float                                       depthBiasClamp,
        float                                       depthBiasSlopeFactor);

- `commandBuffer` is the command buffer into which the command will be recorded.

- `depthBiasConstantFactor` is a scalar factor controlling the constant depth value added to each fragment.

- `depthBiasClamp` is the maximum (or minimum) depth bias of a fragment.

- `depthBiasSlopeFactor` is a scalar factor applied to a fragment’s slope in depth bias calculations.

This command sets the depth bias parameters for subsequent drawing commands when the graphics pipeline is created with `VK_DYNAMIC_STATE_DEPTH_BIAS` set in VkPipelineDynamicStateCreateInfo::`pDynamicStates`. Otherwise, this state is specified by the corresponding VkPipelineRasterizationStateCreateInfo::`depthBiasConstantFactor`, `depthBiasClamp`, and `depthBiasSlopeFactor` values used to create the currently active pipeline.

Valid Usage

- VUID-vkCmdSetDepthBias-depthBiasClamp-00790
  If the `depthBiasClamp` feature is not enabled, `depthBiasClamp` must be `0.0`

Valid Usage (Implicit)

- VUID-vkCmdSetDepthBias-commandBuffer-parameter
  `commandBuffer` must be a valid VkCommandBuffer handle

- VUID-vkCmdSetDepthBias-commandBuffer-recording
  `commandBuffer` must be in the recording state

- VUID-vkCmdSetDepthBias-commandBuffer-cmdpool
  The `VkCommandPool` that `commandBuffer` was allocated from must support graphics operations

- VUID-vkCmdSetDepthBias-videocoding
  This command must only be called outside of a video coding scope

Host Synchronization

- Host access to `commandBuffer` must be externally synchronized

- Host access to the `VkCommandPool` that `commandBuffer` was allocated from must be externally synchronized

Command Properties

Command Buffer Levels | Render Pass Scope | Video Coding Scope | Supported Queue Types
--- | --- | --- | ---
Primary Secondary | Both | Outside | Graphics

#### 27.12.4. Conservative Rasterization

If the `pNext` chain of VkPipelineRasterizationStateCreateInfo includes a `VkPipelineRasterizationConservativeStateCreateInfoEXT` structure, then that structure includes parameters controlling conservative rasterization.

`VkPipelineRasterizationConservativeStateCreateInfoEXT` is defined as:

    // Provided by VK_EXT_conservative_rasterization
    typedef struct VkPipelineRasterizationConservativeStateCreateInfoEXT {
        VkStructureType                                           sType;
        const void*                                               pNext;
        VkPipelineRasterizationConservativeStateCreateFlagsEXT    flags;
        VkConservativeRasterizationModeEXT                        conservativeRasterizationMode;
        float                                                     extraPrimitiveOverestimationSize;
    } VkPipelineRasterizationConservativeStateCreateInfoEXT;

- `sType` is the type of this structure.

- `pNext` is `NULL` or a pointer to a structure extending this structure.

- `flags` is reserved for future use.

- `conservativeRasterizationMode` is the conservative rasterization mode to use.

- `extraPrimitiveOverestimationSize` is the extra size in pixels to increase the generating primitive during conservative rasterization at each of its edges in `X` and `Y` equally in screen space beyond the base overestimation specified in `VkPhysicalDeviceConservativeRasterizationPropertiesEXT`::`primitiveOverestimationSize`. If `conservativeRasterizationMode` is not `VK_CONSERVATIVE_RASTERIZATION_MODE_OVERESTIMATE_EXT`, this value is ignored.

If this structure is not included in the `pNext` chain, `conservativeRasterizationMode` is considered to be `VK_CONSERVATIVE_RASTERIZATION_MODE_DISABLED_EXT`, and and conservative rasterization is disabled.

Polygon rasterization can be made conservative by setting `conservativeRasterizationMode` to `VK_CONSERVATIVE_RASTERIZATION_MODE_OVERESTIMATE_EXT` or `VK_CONSERVATIVE_RASTERIZATION_MODE_UNDERESTIMATE_EXT` in `VkPipelineRasterizationConservativeStateCreateInfoEXT`.

| Note If `conservativePointAndLineRasterization` is supported, conservative rasterization can be applied to line and point primitives, otherwise it must be disabled.

Valid Usage

- VUID-VkPipelineRasterizationConservativeStateCreateInfoEXT-extraPrimitiveOverestimationSize-01769
  `extraPrimitiveOverestimationSize` must be in the range of `0.0` to `VkPhysicalDeviceConservativeRasterizationPropertiesEXT`::`maxExtraPrimitiveOverestimationSize` inclusive

Valid Usage (Implicit)

- VUID-VkPipelineRasterizationConservativeStateCreateInfoEXT-sType-sType
  `sType` must be `VK_STRUCTURE_TYPE_PIPELINE_RASTERIZATION_CONSERVATIVE_STATE_CREATE_INFO_EXT`

- VUID-VkPipelineRasterizationConservativeStateCreateInfoEXT-flags-zerobitmask
  `flags` must be `0`

- VUID-VkPipelineRasterizationConservativeStateCreateInfoEXT-conservativeRasterizationMode-parameter
  `conservativeRasterizationMode` must be a valid VkConservativeRasterizationModeEXT value

    // Provided by VK_EXT_conservative_rasterization
    typedef VkFlags VkPipelineRasterizationConservativeStateCreateFlagsEXT;

`VkPipelineRasterizationConservativeStateCreateFlagsEXT` is a bitmask type for setting a mask, but is currently reserved for future use.

Possible values of VkPipelineRasterizationConservativeStateCreateInfoEXT::`conservativeRasterizationMode`, specifying the conservative rasterization mode are:

    // Provided by VK_EXT_conservative_rasterization
    typedef enum VkConservativeRasterizationModeEXT {
        VK_CONSERVATIVE_RASTERIZATION_MODE_DISABLED_EXT = 0,
        VK_CONSERVATIVE_RASTERIZATION_MODE_OVERESTIMATE_EXT = 1,
        VK_CONSERVATIVE_RASTERIZATION_MODE_UNDERESTIMATE_EXT = 2,
    } VkConservativeRasterizationModeEXT;

- `VK_CONSERVATIVE_RASTERIZATION_MODE_DISABLED_EXT` specifies that conservative rasterization is disabled and rasterization proceeds as normal.

- `VK_CONSERVATIVE_RASTERIZATION_MODE_OVERESTIMATE_EXT` specifies that conservative rasterization is enabled in overestimation mode.

- `VK_CONSERVATIVE_RASTERIZATION_MODE_UNDERESTIMATE_EXT` specifies that conservative rasterization is enabled in underestimation mode.

When overestimate conservative rasterization is enabled, rather than evaluating coverage at individual sample locations, a determination is made of whether any portion of the pixel (including its edges and corners) is covered by the primitive. If any portion of the pixel is covered, then all bits of the coverage mask for the fragment corresponding to that pixel are enabled. If the render pass has a fragment density map attachment and any bit of the coverage mask for the fragment is enabled, then all bits of the coverage mask for the fragment are enabled.

For the purposes of evaluating which pixels are covered by the primitive, implementations can increase the size of the primitive by up to `VkPhysicalDeviceConservativeRasterizationPropertiesEXT`::`primitiveOverestimationSize` pixels at each of the primitive edges. This may increase the number of fragments generated by this primitive and represents an overestimation of the pixel coverage.

This overestimation size can be increased further by setting the `extraPrimitiveOverestimationSize` value above `0.0` in steps of `VkPhysicalDeviceConservativeRasterizationPropertiesEXT`::`extraPrimitiveOverestimationSizeGranularity` up to and including `VkPhysicalDeviceConservativeRasterizationPropertiesEXT`::`extraPrimitiveOverestimationSize`. This may further increase the number of fragments generated by this primitive.

The actual precision of the overestimation size used for conservative rasterization may vary between implementations and produce results that only approximate the `primitiveOverestimationSize` and `extraPrimitiveOverestimationSizeGranularity` properties. Implementations may especially vary these approximations when the render pass has a fragment density map and the fragment area covers multiple pixels.

For triangles if `VK_CONSERVATIVE_RASTERIZATION_MODE_OVERESTIMATE_EXT` is enabled, fragments will be generated if the primitive area covers any portion of any pixel inside the fragment area, including their edges or corners. The tie-breaking rule described in Basic Polygon Rasterization does not apply during conservative rasterization and coverage is set for all fragments generated from shared edges of polygons. Degenerate triangles that evaluate to zero area after rasterization, even for pixels containing a vertex or edge of the zero-area polygon, will be culled if `VkPhysicalDeviceConservativeRasterizationPropertiesEXT`::`degenerateTrianglesRasterized` is `VK_FALSE` or will generate fragments if `degenerateTrianglesRasterized` is `VK_TRUE`. The fragment input values for these degenerate triangles take their attribute and depth values from the provoking vertex. Degenerate triangles are considered backfacing and the application can enable backface culling if desired. Triangles that are zero area before rasterization may be culled regardless.

For lines if `VK_CONSERVATIVE_RASTERIZATION_MODE_OVERESTIMATE_EXT` is enabled, and the implementation sets `VkPhysicalDeviceConservativeRasterizationPropertiesEXT`::`conservativePointAndLineRasterization` to `VK_TRUE`, fragments will be generated if the line covers any portion of any pixel inside the fragment area, including their edges or corners. Degenerate lines that evaluate to zero length after rasterization will be culled if `VkPhysicalDeviceConservativeRasterizationPropertiesEXT`::`degenerateLinesRasterized` is `VK_FALSE` or will generate fragments if `degenerateLinesRasterized` is `VK_TRUE`. The fragments input values for these degenerate lines take their attribute and depth values from the provoking vertex. Lines that are zero length before rasterization may be culled regardless.

For points if `VK_CONSERVATIVE_RASTERIZATION_MODE_OVERESTIMATE_EXT` is enabled, and the implementation sets `VkPhysicalDeviceConservativeRasterizationPropertiesEXT`::`conservativePointAndLineRasterization` to `VK_TRUE`, fragments will be generated if the point square covers any portion of any pixel inside the fragment area, including their edges or corners.

When underestimate conservative rasterization is enabled, rather than evaluating coverage at individual sample locations, a determination is made of whether all of the pixel (including its edges and corners) is covered by the primitive. If the entire pixel is covered, then a fragment is generated with all bits of its coverage mask corresponding to the pixel enabled, otherwise the pixel is not considered covered even if some portion of the pixel is covered. The fragment is discarded if no pixels inside the fragment area are considered covered. If the render pass has a fragment density map attachment and any pixel inside the fragment area is not considered covered, then the fragment is discarded even if some pixels are considered covered.

For triangles, if `VK_CONSERVATIVE_RASTERIZATION_MODE_UNDERESTIMATE_EXT` is enabled, fragments will only be generated if any pixel inside the fragment area is fully covered by the generating primitive, including its edges and corners.

For lines, if `VK_CONSERVATIVE_RASTERIZATION_MODE_UNDERESTIMATE_EXT` is enabled, fragments will be generated if any pixel inside the fragment area, including its edges and corners, are entirely covered by the line.

For points, if `VK_CONSERVATIVE_RASTERIZATION_MODE_UNDERESTIMATE_EXT` is enabled, fragments will only be generated if the point square covers the entirety of any pixel square inside the fragment area, including its edges or corners.

If the render pass has a fragment density map and `VK_CONSERVATIVE_RASTERIZATION_MODE_UNDERESTIMATE_EXT` is enabled, fragments will only be generated if the entirety of all pixels inside the fragment area are covered by the generating primitive, line, or point.

For both overestimate and underestimate conservative rasterization modes a fragment has all of its pixel squares fully covered by the generating primitive must set `FullyCoveredEXT` to `VK_TRUE` if the implementation enables the `VkPhysicalDeviceConservativeRasterizationPropertiesEXT`::`fullyCoveredFragmentShaderInputVariable` feature.

When the use of a shading rate image or setting the fragment shading rate results in fragments covering multiple pixels, coverage for conservative rasterization is still evaluated on a per-pixel basis and may result in fragments with partial coverage. For fragment shader inputs decorated with `FullyCoveredEXT`, a fragment is considered fully covered if and only if all pixels in the fragment are fully covered by the generating primitive.