kc3-lang/angle

2024-08-09T01:03:26

Metal: Properly clear render pass' attachment with an emulated alpha. When a texture is created with emulated format such as RGB, its alpha channel is initialized to 1 and the write mask is configured such that the alpha value won't be overwritten or set to other values. However, if we use this texture as an attachment in a render pass, and DontCare loadAction is used, the alpha value would be initialized with garbage values. No draw calls within the render pass would change these garbage values because the configured write mask already prevents that. Thus the garbage alpha values would be stored in the memory after the render pass ends. This bug also affects MSRTT's unresolve step, because it uses a draw call to blit the resolve texture to the MSAA texture. However, the alpha write is disabled thus the MSAA texture will remain having garbage alpha values. The fix for this bug is that: if we detect that the texture has emulated format and its loadAction is DontCare, we change it to Clear action to clear the alpha channel to 1. Bug: angleproject:42261786 Change-Id: I994849bd4b3c3ab51698833d1cc520376ae6de44 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5773347 Reviewed-by: Kenneth Russell <kbr@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Auto-Submit: Quyen Le <lehoangquyen@chromium.org> Commit-Queue: Quyen Le <lehoangquyen@chromium.org>