VkPhysicalDeviceFragmentShadingRatePropertiesKHR(3)

# VkPhysicalDeviceFragmentShadingRatePropertiesKHR(3) Manual Page

## Name

VkPhysicalDeviceFragmentShadingRatePropertiesKHR - Structure describing variable fragment shading rate limits that can be supported by an implementation

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## C Specification

The `VkPhysicalDeviceFragmentShadingRatePropertiesKHR` structure is defined as:

    // Provided by VK_KHR_fragment_shading_rate
    typedef struct VkPhysicalDeviceFragmentShadingRatePropertiesKHR {
        VkStructureType          sType;
        void*                    pNext;
        VkExtent2D               minFragmentShadingRateAttachmentTexelSize;
        VkExtent2D               maxFragmentShadingRateAttachmentTexelSize;
        uint32_t                 maxFragmentShadingRateAttachmentTexelSizeAspectRatio;
        VkBool32                 primitiveFragmentShadingRateWithMultipleViewports;
        VkBool32                 layeredShadingRateAttachments;
        VkBool32                 fragmentShadingRateNonTrivialCombinerOps;
        VkExtent2D               maxFragmentSize;
        uint32_t                 maxFragmentSizeAspectRatio;
        uint32_t                 maxFragmentShadingRateCoverageSamples;
        VkSampleCountFlagBits    maxFragmentShadingRateRasterizationSamples;
        VkBool32                 fragmentShadingRateWithShaderDepthStencilWrites;
        VkBool32                 fragmentShadingRateWithSampleMask;
        VkBool32                 fragmentShadingRateWithShaderSampleMask;
        VkBool32                 fragmentShadingRateWithConservativeRasterization;
        VkBool32                 fragmentShadingRateWithFragmentShaderInterlock;
        VkBool32                 fragmentShadingRateWithCustomSampleLocations;
        VkBool32                 fragmentShadingRateStrictMultiplyCombiner;
    } VkPhysicalDeviceFragmentShadingRatePropertiesKHR;

## Members

- `sType` is a VkStructureType value identifying this structure.

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

- `minFragmentShadingRateAttachmentTexelSize` indicates minimum supported width and height of the portion of the framebuffer corresponding to each texel in a fragment shading rate attachment. Each value must be less than or equal to the values in `maxFragmentShadingRateAttachmentTexelSize`. Each value must be a power-of-two. It must be (0,0) if the `attachmentFragmentShadingRate` feature is not supported.

- `maxFragmentShadingRateAttachmentTexelSize` indicates maximum supported width and height of the portion of the framebuffer corresponding to each texel in a fragment shading rate attachment. Each value must be greater than or equal to the values in `minFragmentShadingRateAttachmentTexelSize`. Each value must be a power-of-two. It must be (0,0) if the `attachmentFragmentShadingRate` feature is not supported.

- `maxFragmentShadingRateAttachmentTexelSizeAspectRatio` indicates the maximum ratio between the width and height of the portion of the framebuffer corresponding to each texel in a fragment shading rate attachment. `maxFragmentShadingRateAttachmentTexelSizeAspectRatio` must be a power-of-two value, and must be less than or equal to max(`maxFragmentShadingRateAttachmentTexelSize.width` / `minFragmentShadingRateAttachmentTexelSize.height`, `maxFragmentShadingRateAttachmentTexelSize.height` / `minFragmentShadingRateAttachmentTexelSize.width`). It must be 0 if the `attachmentFragmentShadingRate` feature is not supported.

- `primitiveFragmentShadingRateWithMultipleViewports` specifies whether the primitive fragment shading rate can be used when multiple viewports are used. If this value is `VK_FALSE`, only a single viewport must be used, and applications must not write to the `ViewportMaskNV` or `ViewportIndex` built-in when setting `PrimitiveShadingRateKHR`. It must be `VK_FALSE` if the `shaderOutputViewportIndex` feature, the `VK_EXT_shader_viewport_index_layer` extension, or the `geometryShader` feature is not supported, or if the `primitiveFragmentShadingRate` feature is not supported.

- `layeredShadingRateAttachments` specifies whether a shading rate attachment image view can be created with multiple layers. If this value is `VK_FALSE`, when creating an image view with a `usage` that includes `VK_IMAGE_USAGE_FRAGMENT_SHADING_RATE_ATTACHMENT_BIT_KHR`, `layerCount` must be `1`. It must be `VK_FALSE` if the `multiview` feature, the `shaderOutputViewportIndex` feature, the `VK_EXT_shader_viewport_index_layer` extension, or the `geometryShader` feature is not supported, or if the `attachmentFragmentShadingRate` feature is not supported.

- `fragmentShadingRateNonTrivialCombinerOps` specifies whether VkFragmentShadingRateCombinerOpKHR enums other than `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_KEEP_KHR` or `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_REPLACE_KHR` can be used. It must be `VK_FALSE` unless either the `primitiveFragmentShadingRate` or `attachmentFragmentShadingRate` feature is supported.

- `maxFragmentSize` indicates the maximum supported width and height of a fragment. Its `width` and `height` members must both be power-of-two values. This limit is purely informational, and is not validated.

- `maxFragmentSizeAspectRatio` indicates the maximum ratio between the width and height of a fragment. `maxFragmentSizeAspectRatio` must be a power-of-two value, and must be less than or equal to the maximum of the `width` and `height` members of `maxFragmentSize`. This limit is purely informational, and is not validated.

- `maxFragmentShadingRateCoverageSamples` specifies the maximum number of coverage samples supported in a single fragment. `maxFragmentShadingRateCoverageSamples` must be less than or equal to the product of the `width` and `height` members of `maxFragmentSize`, and the sample count reported by `maxFragmentShadingRateRasterizationSamples`. `maxFragmentShadingRateCoverageSamples` must be less than or equal to `maxSampleMaskWords` × 32 if `fragmentShadingRateWithShaderSampleMask` is supported. This limit is purely informational, and is not validated.

- `maxFragmentShadingRateRasterizationSamples` is a VkSampleCountFlagBits value specifying the maximum sample rate supported when a fragment covers multiple pixels. This limit is purely informational, and is not validated.

- `fragmentShadingRateWithShaderDepthStencilWrites` specifies whether the implementation supports writing `FragDepth` or `FragStencilRefEXT` from a fragment shader for multi-pixel fragments. If this value is `VK_FALSE`, writing to those built-ins will clamp the fragment shading rate to (1,1).

- `fragmentShadingRateWithSampleMask` specifies whether the implementation supports setting valid bits of VkPipelineMultisampleStateCreateInfo::`pSampleMask` to `0` for multi-pixel fragments. If this value is `VK_FALSE`, zeroing valid bits in the sample mask will clamp the fragment shading rate to (1,1).

- `fragmentShadingRateWithShaderSampleMask` specifies whether the implementation supports reading or writing `SampleMask` for multi-pixel fragments. If this value is `VK_FALSE`, using that built-in will clamp the fragment shading rate to (1,1).

- `fragmentShadingRateWithConservativeRasterization` specifies whether conservative rasterization is supported for multi-pixel fragments. It must be `VK_FALSE` if `VK_EXT_conservative_rasterization` is not supported. If this value is `VK_FALSE`, using conservative rasterization will clamp the fragment shading rate to (1,1).

- `fragmentShadingRateWithFragmentShaderInterlock` specifies whether fragment shader interlock is supported for multi-pixel fragments. It must be `VK_FALSE` if `VK_EXT_fragment_shader_interlock` is not supported. If this value is `VK_FALSE`, using fragment shader interlock will clamp the fragment shading rate to (1,1).

- `fragmentShadingRateWithCustomSampleLocations` specifies whether custom sample locations are supported for multi-pixel fragments. It must be `VK_FALSE` if `VK_EXT_sample_locations` is not supported. If this value is `VK_FALSE`, using custom sample locations will clamp the fragment shading rate to (1,1).

- `fragmentShadingRateStrictMultiplyCombiner` specifies whether `VK_FRAGMENT_SHADING_RATE_COMBINER_OP_MUL_KHR` accurately performs a multiplication or not. Implementations where this value is `VK_FALSE` will instead combine rates with an addition. If `fragmentShadingRateNonTrivialCombinerOps` is `VK_FALSE`, implementations must report this as `VK_FALSE`. If `fragmentShadingRateNonTrivialCombinerOps` is `VK_TRUE`, implementations should report this as `VK_TRUE`.

## Description

| Note Multiplication of the combiner rates using the fragment width/height in linear space is equivalent to an addition of those values in log2 space. Some implementations inadvertently implemented an addition in linear space due to unclear requirements originating outside of this specification. This resulted in `fragmentShadingRateStrictMultiplyCombiner` being added. Fortunately, this only affects situations where a rate of 1 in either dimension is combined with another rate of 1. All other combinations result in the exact same result as if multiplication was performed in linear space due to the clamping logic, and the fact that both the sum and product of 2 and 2 are equal. In many cases, this limit will not affect the correct operation of applications.

If the `VkPhysicalDeviceFragmentShadingRatePropertiesKHR` structure is included in the `pNext` chain of the VkPhysicalDeviceProperties2 structure passed to vkGetPhysicalDeviceProperties2, it is filled in with each corresponding implementation-dependent property.

These properties are related to fragment shading rates.

Valid Usage (Implicit)

- VUID-VkPhysicalDeviceFragmentShadingRatePropertiesKHR-sType-sType
  `sType` must be `VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_FRAGMENT_SHADING_RATE_PROPERTIES_KHR`

## See Also

VK_KHR_fragment_shading_rate, VkBool32, VkExtent2D, VkSampleCountFlagBits, VkStructureType

## Document Notes

For more information, see the Vulkan Specification

This page is extracted from the Vulkan Specification. Fixes and changes should be made to the Specification, not directly.

## Copyright

Copyright 2014-2023 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0