Apparatus and method for performing depth buffering in a three

Abstract

Disclosed is a three-dimensional display system that utilizes a host processor for performing geometric transformations and a local display processor for processing the user-supplied information which defines the object to be displayed. The display processor creates image data defining the location, color and intensity of each point of the overall image. This display processor processes and stores depth data which defines the corresponding depth relationships of the image points at each location of the overall image with the depth data being stored in a depth buffer, which is part of the display processor. The depth buffer is a two port memory device with one port being a random access port and the other being a serial access port. The display processor pieplines depth buffering operations by loading a row of data from the depth buffer into a shift register and then reading (a Read operation) the relevant pixel data through the serial access port which is connected to the shift register. The display processor then performs the Compare operation between the depth of the new pixel data and the depth of the old pixel data and if appropriate, will perform a Conditional Write operation o=f the new pixel data. The Write operation is performed through the random access port. As a result, the serial access port can continually be used for Read operations during each and every clock cycle, and the random access port can be used for Conditional Write operations during each consecutive clock cycle as well.