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Abstract

A graphics system including a custom graphics and audio processor produces exciting 2D and 3D graphics and surround sound. The system includes a graphics and audio processor including a 3D graphics pipeline and an audio digital signal processor. The graphics pipeline performs Z-buffering and optionally provides memory efficient full scene anti-aliasing (FSAA). When the anti-aliasing rendering mode is selected, Z value bit compression is performed to more efficiently make use of the available Z buffer memory. A Z-clamping arrangement is used to improve the precision of visually important Z components by clamping Z values to zero of pixels that fall within a predetermined Z-axis range near the Z=0 eye/camera (viewport) plane. This allows a Z-clipping plane to be used very close to the eye/camera plane--to avoid undesirable visual artifacts produced when objects rendered near to the eye/camera plane are clipped--while preserving Z value precision for the remaining depth of the scene. In an example implementation, a Z value compression circuit provided in the graphics pipeline is enhanced to effectuate Z-clamping within the predetermined range of Z values. The enhanced circuitry includes an adder for left-shifting an input Z value one or more bits prior to compression and gates for masking out the most significant non-zero shifted bits to zero.

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First Claim