US 7,064,752 B1 · Multi-function unit of a graphics system for updating a hierarchical Z buffer

Abstract

A multi-function unit for occlusion testing primitives being processed in a graphics system and for updating a Z pyramid data structure used for occlusion testing. The Z pyramid data structure is updated on the fly, i.e., as primitives are being occlusion tested. The apparatus comprises multi-function unit is configured to create the Z pyramid data structure and to perform occlusion testing. The Z pyramid data structure comprises a plurality of levels, each of which comprises a plurality of regions. Each region comprises a plurality of subregions, each of which corresponds to a single Z value. Each region corresponds to a plurality of Z values and has a maximum region Z value, which corresponds to the largest Z value of the region. The multi-function unit compares the minimum Z value of each primitive with the maximum Z value of a region associated with the tested primitive to determine whether or not the tested primitive is fully occluded. Coverage masks are maintained by the multi-function unit for the different levels of the Z pyramid data structure to enable the Z pyramid data structure to be updated on the fly. When certain bits in the coverage masks are set, the multi-function unit causes the Z pyramid data structure to be updated.

Claims18

Dependent claims

A multi-function unit of a graphics system, comprising:

a hierarchical tiler configured to occlusion test primitives, the primitives comprising a maximum Z value and a minimum Z value, the maximum and minimum Z values associated with respective X-Y coordinate values, the hierarchical tiler further configured to create a Z pyramid data structure as polygons defined by a plurality of primitives are processed by the multi-function unit;
a parameter interpolator coupled to the hierarchical tiler configured to receive the X-Y coordinate values from the hierarchical tiler and generate a Z value at the pixel level for each received X-Y coordinate value;
a pixel-level comparator coupled to the parameter interpolator configured to determine at a pixel level which values need to be written by a frame buffer controller;
and
a memory unit coupled to the hierarchical tiler and the pixel-level comparator, the memory unit configured to store a change in the Z pyramid data structure responsive to an occlusion test result for a visible primitive before the pixel-level comparator determines whether pixel level values for the visible primitive need to be written by the frame buffer controller.

2 more elements

Dependencies are inferred from the claim text.

Multi-function unit of a graphics system for updating a hierarchical Z buffer

Life of this patent

Multi-function unit of a graphics system for updating a hierarchical Z buffer

Life of this patent

Abstract

Claims18