three.js canvas materials example renders incorrectly

[jdm]

https://threejs.org/examples/canvas_materials.html

[nox]

This one is interesting, AFAICT the 5 aligned balls are properly rendered, and then for the 3 others there are issues with the fact that the drawing buffer is always preserved, and at least 2 of them seem to suffer from coordinate issues.

[nox]

Commenting those two last balls make the demo render correctly with decent perfs.

https://github.com/mrdoob/three.js/blob/2410ad1a8f5844df00191600eafda59def537830/examples/canvas_materials.html#L69-L70

[nox]

This actually has no WebGL involved and the demo was deleted from upstream 15 days ago when they removed CanvasRenderer.