Depth write disable for zone rendering

Abstract

A depth write disable apparatus and method for controlling evictions, such as depth values, from a depth cache to a corresponding depth buffer in a zone rendering system. When the depth write disable circuitry is enabled, evictions from the depth cache (as which typically occur during the rendering of the next zone) to the depth buffer are prevented. In particular, once the depth buffer is initialized (i.e. cleared) to a constant value at the beginning of a scene, the depth buffer does not need to be read. The depth cache handles intermediate depth reads and writes within each zone. Since the memory resident depth buffer is not required after a scene is rendered, it never needs to be written. The final depth values for a zone can thus be discarded (i.e., rather than written to the depth buffer) after each zone is rendering.

Description

technical field [0001] The present invention relates generally to graphics systems, and more particularly to methods and apparatus for controlling the transfer of data from a depth cache to a depth buffer. Background technique [0002] Computer graphics systems are widely used to display graphical representations of objects on two-dimensional video display screens. Current computer graphics systems provide highly detailed representations and are used in a variety of applications. In a typical computer graphics system, objects to be represented on a display screen are broken down into graphics primitives. Primitives are the basic building blocks of graphics displays and can include points, lines, vectors, and polygons such as triangles and quadrilaterals. Typically, hardware / software solutions are implemented to render or draw graphics primitives that represent views of one or more objects being represented on a display screen. [0003] Primitives of a three-dimensional ob...

AI Technical Summary

Problems solved by technology

Writing values ​​to the depth buffer unnecessarily places a considerable load on the memory bus as well as other parts of the system, potentially slowing down the operation of the system

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