VK_QCOM_multiview_per_view_viewports(3)

# VK_QCOM_multiview_per_view_viewports(3) Manual Page

## Name

VK_QCOM_multiview_per_view_viewports - device extension

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## Registered Extension Number

489

## Revision

1

## Ratification Status

Not ratified

## Extension and Version Dependencies

VK_KHR_get_physical_device_properties2

## Contact

- Matthew Netsch mnetsch

## Other Extension Metadata

Last Modified Date

  2022-11-22

IP Status

  No known IP claims.

Interactions and External Dependencies

  - This extension interacts with `VK_KHR_dynamic_rendering`

  - This extension interacts with `VK_EXT_extended_dynamic_state`

Contributors

  - Jeff Leger, Qualcomm

  - Jonathan Tinkham, Qualcomm

  - Jonathan Wicks, Qualcomm

## Description

Certain use cases for multiview have a need for specifying a separate viewport and scissor for each view, without using shader-based viewport indexing as introduced with `VK_EXT_shader_viewport_index_layer`.

This extension adds a new way to control ViewportIndex with multiview. When the `multiviewPerViewViewports` feature is enabled and if the last pre-rasterization shader entry point’s interface does not use the `ViewportIndex` built-in decoration, then each view of a multiview render pass instance will use a viewport and scissor index equal to the `ViewIndex`.

## New Structures

- Extending VkPhysicalDeviceFeatures2, VkDeviceCreateInfo:

  - VkPhysicalDeviceMultiviewPerViewViewportsFeaturesQCOM

## New Enum Constants

- `VK_QCOM_MULTIVIEW_PER_VIEW_VIEWPORTS_EXTENSION_NAME`

- `VK_QCOM_MULTIVIEW_PER_VIEW_VIEWPORTS_SPEC_VERSION`

- Extending VkStructureType:

  - `VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_MULTIVIEW_PER_VIEW_VIEWPORTS_FEATURES_QCOM`

## Issues

1) Is is possible to enable/disable the `multiviewPerViewViewports` feature for individual render pass instances?

RESOLVED: No, when the multiviewPerViewViewports feature is enabled during vkCreateDevice, then all created render pass instances (including dynamic render passes from `VK_KHR_dynamic_rendering`) and all created VkPipelines will have the feature enabled. This approach was chosen because it simplifies application code and there is no known use case enable/disable the feature for individual render passes or pipelines.

2) When this extension is used, is the value of `ViewportIndex` implicitly written by the last pre-rasterization shader stage and can the value of `ViewportIndex` be read in the fragment shader?

RESOLVED: No, use of the extension extension does not add an implicit write to `ViewportIndex` in any shader stage, and additionally, the value of `ViewportIndex` in the fragment shader is undefined.

## Version History

- Revision 1, 2022-11-22 (Jeff Leger)

## See Also

VkPhysicalDeviceMultiviewPerViewViewportsFeaturesQCOM

## 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 2014-2024 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0