Registered Extension Number




Ratification Status

Not ratified

Extension and Version Dependencies


SPIR-V Dependencies


Other Extension Metadata

Last Modified Date


IP Status

No known IP claims.

Interactions and External Dependencies
  • Aaron Hagan, AMD

  • Daniel Rakos, AMD

  • Timothy Lottes, AMD


This extension provides efficient read access to the fragment mask in compressed multisampled color surfaces. The fragment mask is a lookup table that associates color samples with color fragment values.

From a shader, the fragment mask can be fetched with a call to fragmentMaskFetchAMD, which returns a single uint where each subsequent four bits specify the color fragment index corresponding to the color sample, starting from the least significant bit. For example, when eight color samples are used, the color fragment index for color sample 0 will be in bits 0-3 of the fragment mask, for color sample 7 the index will be in bits 28-31.

The color fragment for a particular color sample may then be fetched with the corresponding fragment mask value using the fragmentFetchAMD shader function.

New Enum Constants



New SPIR-V Capabilities


This example shows a shader that queries the fragment mask from a multisampled compressed surface and uses it to query fragment values.

#version 450 core

#extension GL_AMD_shader_fragment_mask: enable

layout(binding = 0) uniform sampler2DMS       s2DMS;
layout(binding = 1) uniform isampler2DMSArray is2DMSArray;

layout(binding = 2, input_attachment_index = 0) uniform usubpassInputMS usubpassMS;

layout(location = 0) out vec4 fragColor;

void main()
    vec4 fragOne = vec4(0.0);

    uint fragMask = fragmentMaskFetchAMD(s2DMS, ivec2(2, 3));
    uint fragIndex = (fragMask & 0xF0) >> 4;
    fragOne += fragmentFetchAMD(s2DMS, ivec2(2, 3), 1);

    fragMask = fragmentMaskFetchAMD(is2DMSArray, ivec3(2, 3, 1));
    fragIndex = (fragMask & 0xF0) >> 4;
    fragOne += fragmentFetchAMD(is2DMSArray, ivec3(2, 3, 1), fragIndex);

    fragMask = fragmentMaskFetchAMD(usubpassMS);
    fragIndex = (fragMask & 0xF0) >> 4;
    fragOne += fragmentFetchAMD(usubpassMS, fragIndex);

    fragColor = fragOne;

Version History

  • Revision 1, 2017-08-16 (Aaron Hagan)

    • Initial draft

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.

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