US Patent 7466322 Clipping graphics primitives to the w=0 plane

Vertices defining a graphics primitive are converted into homogeneous space and clipped against a single clipping plane, the w=0 plane, to produce a clipped graphics primitive having vertices including w coordinates that are greater than or equal to zero. Rasterizing a graphics primitive having a vertex with a w coordinates that is greater than or equal to zero is less complex than rasterizing a graphics primitive having a vertex with a w coordinate that is less than zero. Clipping against the w=0 plane is less complex than conventional clipping since conventional clipping may require that the graphics primitive be clipped against each of the six faces of the viewing frustum to produce a clipped graphics primitive.