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[Impeller] Add ColorBurn, fix SourceOver alpha, make default pipeline initialization robust #33289
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zanderso
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May 12, 2022
impeller/entity/BUILD.gn
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| "shaders/texture_blend.vert", | ||
| "shaders/texture_blend_screen.frag", | ||
| "shaders/texture_blend_screen.vert", | ||
| "shaders/blend.frag", |
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nit: please alphabetize this list.
|
Ended up changing the |
chinmaygarde
approved these changes
May 16, 2022
engine-flutter-autoroll
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May 16, 2022
…pipeline initialization robust (flutter/engine#33289)
houhuayong
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Jun 21, 2022
… initialization robust (flutter#33289)
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In addition to adding ColorBurn and activating advanced blends in the display list dispatcher, this change fixes pipeline alpha blend/default initialization problems that were resulting in double-premultiplied alpha for the SourceOver (default) Entities blend mode. This issue is difficult to notice in isolation, but rapidly compounds with overlapping transparent objects.
SourceOver. The advanced blend shaders just manipulate color channels and pass the source alpha onward for blending. This makes the alpha channel affect the resulting color in the correct way.ScreenandColorBurnin the display list dispatcher.ContentContextOptionsoptions. The default pipeline blend options no longer matchedkSourceOver(the default entities blend mode). Rather than continuing to sync the default pipeline descriptor in the render layer, it's more robust to just apply the same Entities-specificContentContextOptionstransform to the pipeline descriptor in all cases where a new pipeline is created.Screen.Recording.2022-05-11.at.10.33.52.PM.mov
All blend modes now closely match this example: https://fiddle.skia.org/c/@BlendModes
Compare with the previous video I recorded of this test, where a dark outer ring can be seen around the color wheel due to the alpha compositing issues.