# VK_EXT_shader_viewport_index_layer(3) Manual Page

## Name

VK_EXT_shader_viewport_index_layer - device extension

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## Registered Extension Number

163

## Revision

1

## Ratification Status

Not ratified

## Extension and Version Dependencies

None

## SPIR-V Dependencies

- SPV_EXT_shader_viewport_index_layer

## Deprecation State

- Promoted to Vulkan 1.2

## Contact

- Daniel Koch [GitHub]dgkoch

## Other Extension Metadata

Last Modified Date

  2017-08-08

Interactions and External Dependencies

  - This extension provides API support for `GL_ARB_shader_viewport_layer_array`, `GL_AMD_vertex_shader_layer`, `GL_AMD_vertex_shader_viewport_index`, and `GL_NV_viewport_array2`

  - This extension requires the `multiViewport` feature.

  - This extension interacts with the `tessellationShader` feature.

Contributors

  - Piers Daniell, NVIDIA

  - Jeff Bolz, NVIDIA

  - Jan-Harald Fredriksen, ARM

  - Daniel Rakos, AMD

  - Slawomir Grajeswki, Intel

## Description

This extension adds support for the `ShaderViewportIndexLayerEXT` capability from the `SPV_EXT_shader_viewport_index_layer` extension in Vulkan.

This extension allows variables decorated with the `Layer` and `ViewportIndex` built-ins to be exported from vertex or tessellation shaders, using the `ShaderViewportIndexLayerEXT` capability.

When using GLSL source-based shading languages, the `gl_ViewportIndex` and `gl_Layer` built-in variables map to the SPIR-V `ViewportIndex` and `Layer` built-in decorations, respectively. Behavior of these variables is extended as described in the `GL_ARB_shader_viewport_layer_array` (or the precursor `GL_AMD_vertex_shader_layer`, `GL_AMD_vertex_shader_viewport_index`, and `GL_NV_viewport_array2` extensions).

Note | The `ShaderViewportIndexLayerEXT` capability is equivalent to the `ShaderViewportIndexLayerNV` capability added by `VK_NV_viewport_array2`.

## Promotion to Vulkan 1.2

All functionality in this extension is included in core Vulkan 1.2.

The single `ShaderViewportIndexLayerEXT` capability from the `SPV_EXT_shader_viewport_index_layer` extension is replaced by the `ShaderViewportIndex` and `ShaderLayer` capabilities from SPIR-V 1.5 which are enabled by the `shaderOutputViewportIndex` and `shaderOutputLayer` features, respectively. Additionally, if Vulkan 1.2 is supported but this extension is not, these capabilities are optional.

Enabling both features is equivalent to enabling the `VK_EXT_shader_viewport_index_layer` extension.

## New Enum Constants

- `VK_EXT_SHADER_VIEWPORT_INDEX_LAYER_EXTENSION_NAME`

- `VK_EXT_SHADER_VIEWPORT_INDEX_LAYER_SPEC_VERSION`

## New or Modified Built-In Variables

- (modified) `Layer`

- (modified) `ViewportIndex`

## New SPIR-V Capabilities

- `ShaderViewportIndexLayerEXT`

## Version History

- Revision 1, 2017-08-08 (Daniel Koch)

  - Internal drafts

## 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 2014-2024 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0