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nical / lyon

2D graphics rendering on the GPU in rust using path tessellation.
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Line intersection loses lot of accuracy #910

Open SkiFire13 opened 3 weeks ago

SkiFire13 commented 3 weeks ago

Reproduction: run cargo run show "M40000 40000 a 12 12 0 0 0 0 -24" on the main branch (8d6bb2de37765078c66be84f34fc05da483a2e5a)

Result: Screenshot at 24-06-12 ! 09-07-49

The problem seems to be that the conversion step from arc to quadratic bezier involves computing the control point as the intersection of two lines. However due to the (relatively) high coordinates this results in a non-negligible error that really messes up the curve when you zoom in.

In my usecase I have some svgs where the bottom right corner in this numeric range and the errors are pretty evident in that area.

nical commented 3 weeks ago

Thanks for filing this and providing a simple test case. I don't have a lot of time to spend on this these days so I don't promise a fix soon, but your analysis sounds right and it would be worth avoiding the intersection here.