Vulkan: Use subpass to unresolve render-to-texture attachments

GL_EXT_multisampled_render_to_texture allows singlesampled textures to
be used with multisampled framebuffers in such a way that the final
resolve operation is automatically done.  In Vulkan terminology, the
render-to-texture GL attachment is used as a Vulkan subpass resolve
attachment with an implicit (ideally-)lazy-memory multisampled image as
the color attachment.

This extension expects that if the texture is drawn to after the
automatic resolve, the implicit multisampled image would take its
fragment colors from the singlesampled image.  In other words, the
opposite of a resolve operation should be automatically performed at the
start of the render pass.  This change refers to this operation as

The goal of this extension is to allow tiling GPUs to always keep
multisampled data on tile memory and only ever load/store singlesampled
data.  The latter is achieved by using a subpass resolve attachment and
setting storeOp of the multisampled color attachment to DONT_CARE.  This
change achieves the former by using an initial subpass that uses the
resolve attachment as input attachment, draws into the multisampled
color attachment and sets loadOp of said attachment to DONT_CARE.

Bug: angleproject:4881
Change-Id: I99f410530365963567c77a7d62fc9db1500e5e3e
Commit-Queue: Shahbaz Youssefi <>
Reviewed-by: Tim Van Patten <>
Reviewed-by: Jamie Madill <>
17 files changed
tree: 7ef6b39b9601bd0c0cd2b3fb6f22ce3849b502c6
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  5. .style.yapf
  6. .vpython
  7. .vpython3
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  12. DEPS
  14. OWNERS
  16. README.chromium
  19. additional_readme_paths.json
  20. android/
  21. build_overrides/
  22. codereview.settings
  23. doc/
  24. dotfile_settings.gni
  25. extensions/
  26. gni/
  27. include/
  28. infra/
  29. samples/
  30. scripts/
  31. src/
  32. third_party/
  33. tools/
  34. 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, 3.0 and 3.1 to Vulkan, desktop OpenGL, OpenGL ES, Direct3D 9, and Direct3D 11. Future plans include ES 3.2, translation to Metal and MacOS, Chrome OS, and Fuchsia support.

Level of OpenGL ES support via backing renderers

Direct3D 9Direct3D 11Desktop GLGL ESVulkanMetal
OpenGL ES 2.0completecompletecompletecompletecompletein progress
OpenGL ES 3.0completecompletecompletecomplete
OpenGL ES 3.1in progresscompletecompletecomplete
OpenGL ES 3.2in progressin progressin progress

Platform support via backing renderers

Direct3D 9Direct3D 11Desktop GLGL ESVulkanMetal
Mac OS Xcompletein progress
Chrome OScompleteplanned
GGP (Stadia)complete
Fuchsiain progress

ANGLE v1.0.772 was certified compliant by passing the OpenGL ES 2.0.3 conformance tests in October 2011.

ANGLE has received the following certifications with the Vulkan backend:

  • OpenGL ES 2.0: ANGLE 2.1.0.d46e2fb1e341 (Nov, 2019)
  • OpenGL ES 3.0: ANGLE 2.1.0.f18ff947360d (Feb, 2020)
  • OpenGL ES 3.1: ANGLE 2.1.0.f5dace0f1e57 (Jul, 2020)

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, Vulkan 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.