Bug 238328

Summary:	WebGL2 occlusion query works only with early depth test
Product:	WebKit	Reporter:	Juraj Bleho <bleho>
Component:	WebGL	Assignee:	Nobody <webkit-unassigned>
Status:	NEW ---
Severity:	Normal	CC:	dino, kbr, kkinnunen, webkit-bug-importer
Priority:	P2	Keywords:	InRadar
Version:	Safari 15
Hardware:	iPhone / iPad
OS:	iOS 15

Description Juraj Bleho 2022-03-24 08:58:05 PDT

When fragment shader uses discard or gl_FragDepth the result of gl.ANY_SAMPLES_PASSED query is dependent on original depth of fragment instead of modified value from shader.

Comment 1 Radar WebKit Bug Importer 2022-03-24 16:08:38 PDT

<rdar://problem/90799725>

Comment 2 Kenneth Russell 2022-03-24 16:12:43 PDT

Can you offer a minimal test case showing the problem? https://github.com/KhronosGroup/WebGL/tree/main/sdk/tests/conformance2/query has a couple of tests that could be extended.

Would you consider filing this on http://crbug.com/angleproject ? Ideally this will be fixed upstream in ANGLE first and then rolled into WebKit. The same problem likely happens on macOS, at least on M1 hardware.

Comment 3 Juraj Bleho 2022-03-25 02:28:10 PDT

In test you mentioned https://github.com/KhronosGroup/WebGL/tree/main/sdk/tests/conformance2/query just add discard into fragment shader. All pixel should be discarded and result should be 0 but it is 1