System and method for clearing depth and color buffers in a real-time graphics rendering system

Abstract

A method and system for clearing depth and color buffers in a real time graphics rendering system. The method and system are able to improve both depth and color buffer clearing. The method and system may utilize a frame flag, a depth clearing module, and a fast color and frame flag clearing module. The system assigns a frame flag to each pixel, which is used to determine whether the current Z value for the pixel is valid. The frame flag may be attached to Z value in the depth buffer. Instead of filling entire depth and color buffers with background values, the system only fills the holes that were not drawn in the previous frame. The fast color and frame flag clearing module traverses a rectangular area, tile by tile, where a tile is a block of pixels, to determine whether each pixel is background by checking the frame flags that are read from the depth buffer. If at least one pixel of a tile is background, the module updates those pixels' color with background color by sending requests to memory interface.