[Impeller] Fix perspective clips with a large perspective bias#181434
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This pull request fixes incorrect clipping for geometries under a perspective transform with a large bias. The main change is in the clip.vert shader, which now correctly lets the GPU handle perspective division and clipping by not dividing gl_Position by w in the vertex shader. Instead, it sets gl_Position.z relative to w. Complementing this, FillRectGeometry::GetCoverage is updated to use TransformAndClipBounds for accurate coverage calculation with perspective transforms. A new playground test is also added for visual verification. The changes are correct and address the issue effectively.
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LGTM. The math should be equivalent. Previously the weight was set to 1 by applying the division, then undoing that for the z component to maintain the clip depth. This works similarly but keeps the weight value intact by just multiplying it by the weight instead. My intuition here is that we are getting different results by delaying the weight division instead of doing it here.
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flutter/flutter@bfc9041...def9ca9 2026-01-25 [email protected] Roll Skia from f1433eb44a50 to 2830fbe8bafe (1 revision) (flutter/flutter#181464) 2026-01-25 [email protected] Roll Fuchsia Linux SDK from 6xoKGIry6Y8T8x5Sa... to T4qTEa3T5CCSCIoJY... (flutter/flutter#181458) 2026-01-24 [email protected] Roll Skia from b6d396a151bc to f1433eb44a50 (1 revision) (flutter/flutter#181449) 2026-01-24 [email protected] Roll Dart SDK from 29918a54dd5c to 60553fc4c04f (1 revision) (flutter/flutter#181437) 2026-01-24 [email protected] Roll Fuchsia Linux SDK from n7NohL9DPpEuPjNt9... to 6xoKGIry6Y8T8x5Sa... (flutter/flutter#181438) 2026-01-24 [email protected] [Impeller] Fix perspective clips with a large perspective bias (flutter/flutter#181434) 2026-01-24 [email protected] Roll Dart SDK from e82d7ad1855e to 29918a54dd5c (4 revisions) (flutter/flutter#181435) 2026-01-24 [email protected] Roll Skia from 32b52343e757 to b6d396a151bc (4 revisions) (flutter/flutter#181431) 2026-01-24 [email protected] [Impeller] Fix interpolation error in Rect::TransformAndClipBounds (flutter/flutter#181420) 2026-01-23 [email protected] Roll Skia from 6d438894c2a8 to 32b52343e757 (2 revisions) (flutter/flutter#181419) 2026-01-23 [email protected] [Material] modernize Typography._withPlatform with Dart 3 switch expression (flutter/flutter#181398) 2026-01-23 [email protected] CupertinoSheetRoute with scrolling and dragging (flutter/flutter#177337) 2026-01-23 [email protected] Adds contents of keys file when a skia gold error occurs. (flutter/flutter#181401) 2026-01-23 [email protected] Roll Skia from e4bd0a355e68 to 6d438894c2a8 (3 revisions) (flutter/flutter#181405) 2026-01-23 [email protected] bump KGP and AGP max known versions (flutter/flutter#181325) 2026-01-23 [email protected] Roll Skia from db10db8bd55f to e4bd0a355e68 (3 revisions) (flutter/flutter#181391) 2026-01-23 [email protected] Roll Packages from 9010299 to 5af5f50 (4 revisions) (flutter/flutter#181388) 2026-01-23 [email protected] Look for project root for FeatureFlags manifest (flutter/flutter#180689) If this roll has caused a breakage, revert this CL and stop the roller using the controls here: https://autoroll.skia.org/r/flutter-packages Please CC [email protected],[email protected] on the revert to ensure that a human is aware of the problem. To file a bug in Packages: https://github.com/flutter/flutter/issues/new/choose To report a problem with the AutoRoller itself, please file a bug: https://issues.skia.org/issues/new?component=1389291&template=1850622 Documentation for the AutoRoller is here: https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md
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…er#181434) Fixes: flutter#173104 We were precomputing the perspective adjustment inside the clipping vertex shader, which prevented the GPU from performing correct clipping against the camera plane.
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Fixes: #173104
We were precomputing the perspective adjustment inside the clipping vertex shader, which prevented the GPU from performing correct clipping against the camera plane.