[blauditore]

If you can't stitch polygons together seamlessly, how can you be sure the background doesn't bleed through with sampling? Isn't computing the exact coverage the same as having infinitely many point samples? The bleed-through of the background would then also be proportional to the gap between polygons, so if that one's small, the bleeding would be minor as well.

[codeflo]

No, in animated models, there is no gap between polygons. And if you only compute single-polygon coverage, you can’t determine whether for two polygons that each cover 50% of a pixel, they both cover the same 50%, or complementary 50%, or anything in between. In practice, systems like that tend to show something like 25% background, 25% polygon A and 50% polygon B for the seam pixels, depending on draw order. That is, you get 25% background bleed.