Structure, apparatus, and method for performing conservative hidden surface
removal in a graphics processor. Culling is divided into two steps, a
magnitude comparison content addressable memory cull operation (MCCAM
Cull), and a subpixel cull operation. The MCCAM Cull discards primitives
that are hidden completely by previously processed geometry. The Subpixel
Cull takes the remaining primitives (which are partly or entirely
visible), and determines the visible fragments. In one embodiment the
method of performing hidden surface removal includes: selecting a current
primitive comprising a plurality of stamps; comparing stamps to stamps
from previously evaluated primitives; selecting a first stamp as a
currently potentially visible stamp (CPVS) based on a relationship of
depth states of samples in the first stamp with depth states of samples of
previously evaluated stamps; comparing the CPVS to a second stamp;
discarding the second stamp when no part of the second stamp would affect
a final graphics display image based on the stamps that have been
evaluated; discarding the CPVS and making the second stamp the CPVS, when
the second stamp hides the CPVS; dispatching the CPVS and making the
second stamp the CPVS when both the second stamp and the CPVS are at least
partially visible in the final graphics display image; and dispatching the
second stamp and the CPVS when the visibility of the second stamp and the
CPVS depends on parameters evaluated later in the computer graphics
pipeline.