[split] Teemu's Part Checker

[Philippe Hurbain]

It partly depends on the size of the polygons but it can really cause seams due to rounding errors.

This because the rasterizer doesn't guarantee the calculated final position of the projected vertex is (still) exactly on the companion polygon's side. This can cause a single pixel offset resulting in a seam.

See also:
https://computergraphics.stackexchange.c...-in-cracks

It can also upset normal calculations, because weird jumps in smoothness could occur if the two t-juncted polygons aren't on the same plane.

I know the rationale behind that, I just say that if you SEE no problem, then there IS no problem having T-junctions. And actually it's fairly rare you see artifacts (at least in planar surfaces)