Vulkan: Emulate subgroup ops in seamful cubemap emulation

Where subgroup ops are not available, they are emulated as such:

Code with subgroup ops:

    float lH = subgroupQuadSwapHorizontal(layer);
    float lV = subgroupQuadSwapVertical(layer);
    float lD = subgroupQuadSwapDiagonal(layer);

    bool isHelperH = subgroupQuadSwapHorizontal(gl_HelperInvocation);
    bool isHelperV = subgroupQuadSwapVertical(gl_HelperInvocation);

    if (gl_HelperInvocation)
        layer = !isHelperH ? lH : !isHelperV ? lV : lD;

Emulated code:

    float nonHelperLayer = gl_HelperInvocation ? 0.0 : layer;
    float lH = abs(dFdxFine(nonHelperLayer));
    float lV = abs(dFdyFine(nonHelperLayer));
    float lD = abs(dFdxFine(lV));

    float isHelperDiffH = abs(dFdxFine(float(gl_HelperInvocation)));
    bool isNonHelperH = isHelperDiffH > 0.5;

    float isHelperDiffV = abs(dFdyFine(float(gl_HelperInvocation)));
    bool isNonHelperV = isHelperDiffV > 0.5;

    if (gl_HelperInvocation)
        layer = isNonHelperH ? lH : isNonHelperV ? lV : lD;

Both paths are supported as on nvidia devices the emulated code
misbehaves.  This change therefore effectively only enables seamful cube
map emulation on Android where subgroup operations are not supported.

Bug: angleproject:3243
Bug: angleproject:3732
Change-Id: I9664d9760756758748183eb121c626f176789f3a
Reviewed-by: Shahbaz Youssefi <>
Commit-Queue: Shahbaz Youssefi <>
12 files changed
tree: df65513b64cde80c81072648544e1ba9f641f5d0
  1. .clang-format
  2. .gitattributes
  3. .gitignore
  4. .gn
  5. .style.yapf
  9. DEPS
  11. OWNERS
  13. README.chromium
  16. additional_readme_paths.json
  17. android/
  18. build_overrides/
  19. codereview.settings
  20. doc/
  21. dotfile_settings.gni
  22. extensions/
  23. gni/
  24. include/
  25. infra/
  26. samples/
  27. scripts/
  28. src/
  29. third_party/
  30. tools/
  31. util/

ANGLE - Almost Native Graphics Layer Engine

The goal of ANGLE is to allow users of multiple operating systems to seamlessly run WebGL and other OpenGL ES content by translating OpenGL ES API calls to one of the hardware-supported APIs available for that platform. ANGLE currently provides translation from OpenGL ES 2.0 and 3.0 to desktop OpenGL, OpenGL ES, Direct3D 9, and Direct3D 11. Support for translation from OpenGL ES to Vulkan is underway, and future plans include compute shader support (ES 3.1) and MacOS support.

Level of OpenGL ES support via backing renderers

Direct3D 9Direct3D 11Desktop GLGL ESVulkan
OpenGL ES 2.0completecompletecompletecompletecomplete
OpenGL ES 3.0completecompletecompletein progress
OpenGL ES 3.1in progresscompletecompletenot started
OpenGL ES 3.2plannedplannedplanned

Platform support via backing renderers

Direct3D 9Direct3D 11Desktop GLGL ESVulkan
Mac OS Xcomplete
Chrome OScompleteplanned
Fuchsiain progress

ANGLE v1.0.772 was certified compliant by passing the ES 2.0.3 conformance tests in October 2011. ANGLE also provides an implementation of the EGL 1.4 specification.

ANGLE is used as the default WebGL backend for both Google Chrome and Mozilla Firefox on Windows platforms. Chrome uses ANGLE for all graphics rendering on Windows, including the accelerated Canvas2D implementation and the Native Client sandbox environment.

Portions of the ANGLE shader compiler are used as a shader validator and translator by WebGL implementations across multiple platforms. It is used on Mac OS X, Linux, and in mobile variants of the browsers. Having one shader validator helps to ensure that a consistent set of GLSL ES shaders are accepted across browsers and platforms. The shader translator can be used to translate shaders to other shading languages, and to optionally apply shader modifications to work around bugs or quirks in the native graphics drivers. The translator targets Desktop GLSL, Direct3D HLSL, and even ESSL for native GLES2 platforms.


ANGLE repository is hosted by Chromium project and can be browsed online or cloned with

git clone


View the Dev setup instructions.