Apparatus and method for fragment operations in a 3d-graphics pipeline

Abstract

Apparatus and methods for rendering 3D graphics images. The apparatus include a port for receiving commands from a graphics application, an output for sending a rendered image to a display and a fragment-operations pipeline, coupled to the port and to the output, the pipeline including a stage for performing a fragment operation on a fragment on a per-pixel basis, as well as a stage for performing a fragment operation on the fragment on a per-sample basis. The stage for performing on a per-pixel basis is one of the following: a scissor-test stage, a stipple-test stage, an alpha-test stage or a colorest stage, and the stage for performing on a per-sample basis is one of the following: a Z-test stage, a blending stage or a dithering stage. The apparatus programmatically selects whether to perform a stencil test on a per-pixel or a per-sample basis and performs the stencil test on the selected basis. The apparatus also programmatically selects pixel samples for per-sample operations, where the sample selections differ with different instances of the same per-sample operation. The apparatus also programmatically selects a set of subdivisions of a pixel as samples for use in the per-sample fragment operation, programmatically assigns different weights to at least two samples in the set and performs the per-sample fragments operation on the fragment using the programmatically selected and differently weighted samples.