1  include::meta/VK_AMD_shader_fragment_mask.txt[]
 2  
 3  *Last Modified Date*::
 4      2017-08-16
 5  *IP Status*::
 6      No known IP claims.
 7  *Dependencies*::
 8    - Requires the
 9      https://www.khronos.org/registry/spir-v/extensions/AMD/SPV_AMD_shader_fragment_mask.html[`SPV_AMD_shader_fragment_mask`]
10      SPIR-V extension.
11  *Contributors*::
12    - Aaron Hagan, AMD
13    - Daniel Rakos, AMD
14    - Timothy Lottes, AMD
15  
16  This extension provides efficient read access to the fragment mask in
17  compressed multisampled color surfaces.
18  The fragment mask is a lookup table that associates color samples with color
19  fragment values.
20  
21  From a shader, the fragment mask can be fetched with a call to
22  code:fragmentMaskFetchAMD, which returns a single code:uint where each
23  subsequent four bits specify the color fragment index corresponding to the
24  color sample, starting from the least significant bit.
25  For example, when eight color samples are used, the color fragment index for
26  color sample 0 will be in bits 0-3 of the fragment mask, for color sample 7
27  the index will be in bits 28-31.
28  
29  The color fragment for a particular color sample may then be fetched with
30  the corresponding fragment mask value using the code:fragmentFetchAMD shader
31  function.
32  
33  === New Object Types
34  
35  None.
36  
37  === New Enum Constants
38  
39  None.
40  
41  === New Enums
42  
43  None.
44  
45  === New SPIR-V Capabilities
46  
47    * <<spirvenv-capabilities-table-fragmentmaskamd, code:FragmentMaskAMD>>
48  
49  === New Structures
50  
51  None.
52  
53  === New Functions
54  
55  None.
56  
57  === Examples
58  
59  This example shows a shader that queries the fragment mask from a
60  multisampled compressed surface and uses it to query fragment values.
61  
62  [source,c++]
63  ----------------------------------------
64  #version 450 core
65  
66  #extension GL_AMD_shader_fragment_mask: enable
67  
68  layout(binding = 0) uniform sampler2DMS       s2DMS;
69  layout(binding = 1) uniform isampler2DMSArray is2DMSArray;
70  
71  layout(binding = 2, input_attachment_index = 0) uniform usubpassInputMS usubpassMS;
72  
73  layout(location = 0) out vec4 fragColor;
74  
75  void main()
76  {
77      vec4 fragOne = vec4(0.0);
78  
79      uint fragMask = fragmentMaskFetchAMD(s2DMS, ivec2(2, 3));
80      uint fragIndex = (fragMask & 0xF0) >> 4;
81      fragOne += fragmentFetchAMD(s2DMS, ivec2(2, 3), 1);
82  
83      fragMask = fragmentMaskFetchAMD(is2DMSArray, ivec3(2, 3, 1));
84      fragIndex = (fragMask & 0xF0) >> 4;
85      fragOne += fragmentFetchAMD(is2DMSArray, ivec3(2, 3, 1), fragIndex);
86  
87      fragMask = fragmentMaskFetchAMD(usubpassMS);
88      fragIndex = (fragMask & 0xF0) >> 4;
89      fragOne += fragmentFetchAMD(usubpassMS, fragIndex);
90  
91      fragColor = fragOne;
92  }
93  ----------------------------------------
94  
95  === Version History
96  
97    * Revision 1, 2017-08-16 (Aaron Hagan)
98      - Initial draft