vkGetPhysicalDeviceFragmentShadingRatesKHR(3)

# vkGetPhysicalDeviceFragmentShadingRatesKHR(3) Manual Page

## Name

vkGetPhysicalDeviceFragmentShadingRatesKHR - Get available shading rates for a physical device

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## C Specification

To query available shading rates, call:

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

## Parameters

- `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.

## Description

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

On success, this command returns

  - `VK_SUCCESS`

  - `VK_INCOMPLETE`

On failure, this command returns

  - `VK_ERROR_OUT_OF_HOST_MEMORY`

## See Also

VkPhysicalDevice, VkPhysicalDeviceFragmentShadingRateKHR

## 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 2014-2021 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0