Graphical rendering system using simultaneous parallel query Z-buffer and method therefor

Abstract

Apparatus and method for a Parallel Query Z-coordinate Buffer <DEL-S DATE="20030415" ID="DEL-S-00001" / >are described. The apparatus and method<DEL-E ID="DEL-S-00001" / > perform a keep / discard decision on screen coordinate geometry before the geometry is converted or rendered into individual display screen pixels by implementing a parallel searching technique within a novel z-coordinate buffer based on a novel magnitude comparison content addressable memory (MCCAM) structure. The MCCAM provides <DEL-S DATE="20030415" ID="DEL-S-00002" / >means<DEL-E ID="DEL-S-00002" / > <INS-S DATE="20030415" ID="INS-S-00001" / >structure and method <INS-E ID="INS-S-00001" / >for performing simultaneous arithmetic magnitude comparisons on numerical quantities. These arithmetic magnitude comparisons include arithmetic less-than, greater-than, less-than-or-equal to, and greater-than-or-equal-to operations between coordinate values of a selected graphical object and the coordinate values of other objects in the image scene which may or may not occult the selected graphical object. <DEL-S DATE="20030415" ID="DEL-S-00003" / >Embodiments of the method and apparatus utilizing variations<DEL-E ID="DEL-S-00003" / > <INS-S DATE="20030415" ID="INS-S-00002" / >The structure and method support variations and combinations <INS-E ID="INS-S-00002" / >of bounding box occulting tests, vertex bounding box occulting tests, span occulting tests, and raster-write occulting tests<DEL-S DATE="20030415" ID="DEL-S-00004" / >, as well as combinations of these tests are described<DEL-E ID="DEL-S-00004" / > .

Description

FIELD OF THE INVENTIONThe field of this invention is twofold: 1) three-dimensional computer graphics, and more specifically, hidden surface removal in three-dimensional rendering; and 2) computer memories, and more specifically, Content Addressable Memories (CAM).BACKGROUND OF THE INVENTIONThree-dimensional Computer GraphicsComputer graphics is the art and science of generating pictures with a computer. Generation of pictures is commonly called rendering. Generally, in three-dimensional computer graphics, geometry that represents surfaces (or volumes) of objects in a scene is translated into pixels stored in a frame buffer, and then displayed on a display device, such as a CRT.Pixels may have a direct one-to-one correspondence with physical display device hardware, but this is not always the case. Some three-dimensional graphics systems reduce aliasing with a frame buffer that has multiple pixels per physical display picture element. Other 3D graphics systems, in order to reduce the...

AI Technical Summary

Benefits of technology

The MCCAM Z-buffer 11000, 23000, or 39000 performs a keep / discard decision on all pixels (or, as described later, on groups of pixels called Cells) at once. The MCCAM Z-buffer 11000, 23000 or 39000 achieves this parallelism by including a set of arithmetic comparators in every memory word that stores a pixel's z-value. The operation of performing a keep / discard decision on all pixels at once is called a "parallel query" of the MCCAM Z-buffer 11000, 23000 or 39000. Parallel query operations enhance performance of Pixel Drawing Pipelines 8000, 20000, 29000, or 32000 by providing Occulting Tests 9000, 22000, 27000, or 30000 that can quickly determine if an entire object or graphics primitive is occulted before it undergoes rasterization.

Novel VLSI circuits 48000, 49000, 49000, 51000, 52000, 53000, 54000, 55000, 58000, and 59000 for efficiently implementing the MCCAM Z-buffer 11000, 23000 or 39000 are included in the invention.

Problems solved by technology

Pixels may have a direct one-to-one correspondence with physical display device hardware, but this is not always the case.

As scene models become more and more complicated, renderers will be required to process scenes of ever increasing depth complexity.

One drawback to the Z-buffer hidden surface removal method is the requirement for geometry to be converted to pixel values before hidden surface removal can be done.

One major drawback to the prior art Z-buffer is its inherently pixel-sequential nature.

For scenes with high depth complexity, access to the Z-buffer is a bottleneck which limits performance in renderers.

Prior art rendering systems do not gain much from taking advantage of temporal correlation because they will only save computations at the very end of the graphics pipeline 1000.

On top of this, taking advantage of temporal correlation is difficult in prior art rendering systems because, the "backward link" from the final values in the Z-buffer and frame buffer back to the geometry database is difficult to construct.

It is inefficient to perform magnitude comparisons in a equality-testing CAM because a large number of clock cycles is required to do the task.

CAMs are not used in any practical prior art renders.

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