1643236 - Incorrect rendering of perspective transformed pictures that intersect the viewport bounds

Status: NEW

(Core :: Graphics: WebRender, defect, P3)

Description

[Connor Brewster [:cbrewster]]

Attachment: test-case.html

(Moving from bug 1642549)

We sometimes incorrectly render pictures with perspective transforms that intersect the viewport bounds. When looking at the render targets, it looks like we clip too much of the transformed picture's content. This leads to the texture stretching at its UV bounds seen in the test case.

Comment 1

[Connor Brewster [:cbrewster]]

Attachment: screenshot.png

Comment 2

[Jessie [:jbonisteel] pls NI]

Hey Jeff - I see you have marked this as blocking wr-79 - what are the next steps? Who should look at this?

Comment 3

[Jeff Muizelaar [:jrmuizel]]

Perhaps Dzmitry or Connor? I'm not actually certain of the severity of this so put in wr-79 so we wouldn't forget about it. If it's not severe than we can drop it from the list.

Comment 4

[Jessie [:jbonisteel] pls NI]

Hey Kvark, Connor - can either of you comment on the severity of this issue? Is this something we should fix right away?

Comment 5

[Dzmitry Malyshau [:kvark]]

I don't think this is urgent/blocking, unless there is a popular resource that happens to be affected.
If Connor is right, and shifting the near plane is enough, this is fairly easy to test.

Comment 6

[Connor Brewster [:cbrewster]]

I did some testing with mozregression and it looks like this bug has been around for a while, it is present in builds going back to early 2019 (builds before this did not handle perspective rendering properly at all). Since we haven't had any reports of this being a problem, I think this is low severity.

That being said, it is noticeable when moving really close to the walls and looking around in the CSS FPS demo: https://keithclark.co.uk/labs/css-fps/desktop/