VK_QCOM_render_pass_shader_resolve(3)

# VK_QCOM_render_pass_shader_resolve(3) Manual Page

## Name

VK_QCOM_render_pass_shader_resolve - device extension

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## Registered Extension Number

172

## Revision

4

## Extension and Version Dependencies

- Requires Vulkan 1.0

### Other Extension Metadata

Last Modified Date

  2019-11-07

IP Status

  No known IP claims.

Interactions and External Dependencies

  None.

Contributors

  - Srihari Babu Alla, Qualcomm

  - Bill Licea-Kane, Qualcomm

  - Jeff Leger, Qualcomm

### Description

This extension allows a shader resolve to replace fixed-function resolve.

Fixed-function resolve is limited in function to simple filters of multisample buffers to a single sample buffer.

Fixed-function resolve is more performance efficient and/or power efficient than shader resolve for such simple filters.

Shader resolve allows a shader writer to create complex, non-linear filtering of a multisample buffer in the last subpass of a subpass dependency chain.

This extension also provides a bit which can be used to enlarge a sample region dependency to a fragment region dependency, so that a framebuffer-region dependency can replace a framebuffer-global dependency in some cases.

### New Enum Constants

- `VK_QCOM_RENDER_PASS_SHADER_RESOLVE_EXTENSION_NAME`

- `VK_QCOM_RENDER_PASS_SHADER_RESOLVE_SPEC_VERSION`

- Extending VkSubpassDescriptionFlagBits:

  - `VK_SUBPASS_DESCRIPTION_FRAGMENT_REGION_BIT_QCOM`

  - `VK_SUBPASS_DESCRIPTION_SHADER_RESOLVE_BIT_QCOM`

### Issues

1) Should this extension be named render_pass_shader_resolve?

RESOLVED Yes.

This is part of suite of small extensions to render pass.

Following the style guide, instead of following VK_KHR_create_renderpass2.

2) Should the VK_SAMPLE_COUNT_1_BIT be required for each pColorAttachment and the DepthStencilAttachent?

RESOLVED No.

While this may not be a common use case, and while most fixed-function resolve hardware has this limitation, there is little reason to require a shader resolve to resolve to a single sample buffer.

3) Should a shader resolve subpass be the last subpass in a renderpass?

RESOLVED Yes.

To be more specific, it should be the last subpass in a subpass dependency chain.

4) Do we need the `VK_SUBPASS_DESCRIPTION_FRAGMENT_REGION_BIT_QCOM` bit?

RESOLVED Yes.

This applies when an input attachment’s sample count is equal to `rasterizationSamples`. Further, if `sampleShading` is enabled (explicitly or implicitly) then `minSampleShading` must equal 0.0.

However, this bit may be set on any subpass, it is not restricted to a shader resolve subpass.

### Version History

- Revision 1, 2019-06-28 (wwlk)

  - Initial draft

- Revision 2, 2019-11-06 (wwlk)

  - General clean-up/spec updates

  - Added issues

- Revision 3, 2019-11-07 (wwlk)

  - Typos

  - Additional issues

  - Clarified that a shader resolve subpass is the last subpass in a subpass dependency chain

- Revision 4, 2020-01-06 (wwlk)

  - Change resolution of Issue 1 (render_pass, not renderpass)

## See Also

No cross-references are available

## Document Notes

For more information, see the Vulkan Specification

This page is a generated document. Fixes and changes should be made to the generator scripts, not directly.

## Copyright

Copyright (c) 2014-2020 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0