This is based on Timur Kristof's code, but there are a lot of differences.
The idea is that it doesn't just compute an intersection between a point
and a triangle. It computes the *distance* between a point and a triangle
and it does so in screen space. It accurately takes the subpixel precision
of the rasterizer into account, so that it works optimally at all
resolutions, all MSAA modes, and all quant modes.
The distance computation is only approximated because it only considers
the infinite lines going through triangle edges. However, it seems to be
more than sufficient in practice because the existing rounding-based small
prim culling compensates for it.
The performance improvement is up to 10% in some geometry-bound tests,
though targeted microbenchmarks can show a lot more than that.
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33361>
Marek Olšák
ce716d009f