I found that the Mozilla Monument name finder shows visual artifacts with webrender enabled. URL: http://thewebrocks.com/demos/mozilla-monument-name-finder/ You can see the artifacts in the bottom descriptions mostly. For a clearer test case, visit http://thewebrocks.com/demos/3D-css-tester/

http://thewebrocks.com/demos/3D-css-tester/ mozregression --good 2017-09-15 --bad 2017-11-26 --pref "layers.acceleration.force-enabled:true" "gfx.webrender.enabled:true" "gfx.webrendest.enabled:true" "gfx.webrender.layers-free:true" "gfx.webrender.blob-images:true" > 13:29.58 INFO: Last good revision: f7b7bdd7b05c992b4fb435a26a6278829063748b > 13:29.58 INFO: First bad revision: b7bc562d77f1f987b623c11cd6e6713f7be2c846 > 13:29.58 INFO: Pushlog: > https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=f7b7bdd7b05c992b4fb435a26a6278829063748b&tochange=b7bc562d77f1f987b623c11cd6e6713f7be2c846 > b7bc562d77f1 Kartikaya Gupta — Bug 1419440 - Update for API change in WR PR 2082. r=mstange > 85a4275ed544 Dzmitry Malyshau — Bug 1419440 - Update for API changes in WR PR 2050. r=kats > 4bd54453fd2e Kartikaya Gupta — Bug 1419440 - Update webrender to commit b7b07562fda338fcb2faff66ce01aafb6235fbcf. r=mstange

Nightly 59 x64 20171126100425 de_DE 3e14872b31a7b1b207605d09b78fbaaf21f1bba7 @ Debian Testing (KDE, Radeon RX480) fresh profile: layers.acceleration.force-enabled, gfx.webrender.enabled, gfx.webrender.blob-images (vs. https://packages.debian.org/de/buster/firefox-esr on the right side)

I used the try pushes in bug 1419440 to narrow this down further, it was introduced in the range 5019eb12c3e36053e02c0fdc4121604b4a0fdd3d..02d9b6d939b92ab8f1cc5bdf6d69bc4b4fccf554 which is these changes: * 02d9b6d9 Auto merge of #2078 - kvark:rtree, r=glennw |\ | * 08a32a9e RenderTaskTree refactor * | 0cc47eb8 Auto merge of #2072 - nical:dbg-flags, r=glennw |\ \ | * | b32c990d Make servo-tidy happy. | * | 72161329 Add toggle_debug_flags. | * | 1365e063 Properly handle debug flags when creating the renderer. | * | 0d934778 Use DebugFlags for time and sample queries. | / * | e83612df Auto merge of #2069 - glennw:xf, r=kvark |\ \ | * | 0aebe2b7 Address review comments | * | 8253bbb3 Remove manual interpolation of local space in transform shaders. | / * | 00e70b3c Auto merge of #2077 - kvark:pass-kind, r=glennw |/ * 40349b38 Strong typing for the main framebuffer pass

Glenn, you wrote or reviewed all of the above PRs, do you know which of the changes might be responsible for this bug? (Or what the underlying problem might be?)

Bug 1420754 has the same regression range.

@ e83612df - https://treeherder.mozilla.org/#/jobs?repo=try&revision=9c24dd30bb30c2e35207df67f19526759e4d4953 is bad, which narrows the regression range to: * | e83612df Auto merge of #2069 - glennw:xf, r=kvark |\ \ | * | 0aebe2b7 Address review comments | * | 8253bbb3 Remove manual interpolation of local space in transform shaders. | / * | 00e70b3c Auto merge of #2077 - kvark:pass-kind, r=glennw |/ * 40349b38 Strong typing for the main framebuffer pass

@ 00e70b3c - https://treeherder.mozilla.org/#/jobs?repo=try&revision=ae08109c68f80e49aa203cda6bb7a6e0217c6b90 is good, so that narrows it to: * | e83612df Auto merge of #2069 - glennw:xf, r=kvark |\ \ | * | 0aebe2b7 Address review comments | * | 8253bbb3 Remove manual interpolation of local space in transform shaders. So definitely from servo/webrender#2069.

It's not immediately clear to me why that would have caused artifacts. I've self-assigned the related GH bug to investigate further.

The "related GH bug" is https://github.com/servo/webrender/issues/2133

WR isn't shipping in 59, right? Assuming that's correct, marking 59:fix-optional.

This should be fixed by the next WR update.

Fixed in today's nightly.