ef5c036d1c
This is UV barycentric interpolation failing for triangles where vertices are colinear in screen space. To fix this, we detect this early on so we do the interpolation on edges instead of triangles. Such triangles will never be painted on unless we have occlusion and culling off (since, arguably they are self occluded and almost back-facing). The code still does not fill the whole area but this can be checked separately.