 Rasterization

Rasterization converts geometric primitives into candidate contributions at discrete pixel sample positions. For a projected triangle, an implementation tests which samples lie inside its three oriented edges and interpolates attributes from the vertices. With barycentric coordinates ${\lambda }_i$, a screen-space linear attribute is ${\sum }_i{\lambda }_i{a}_i$. Attributes defined before perspective projection generally need perspective-correct interpolation:Here $w_i$ are the clip-coordinate denominators. Ordinary interpolation would distort a texture seen at an angle.

A generated fragment is not necessarily a final visible pixel: a fragment shader determines its values, a depth buffer can reject hidden contributions, and blending combines surviving contributions. Multiple samples per pixel improve coverage estimates near boundaries but do not recreate arbitrarily fine detail. OpenGL specifies these stages separately, so geometric coverage and final image storage must not be conflated.^[ref]