| 摘要 |
<p>PURPOSE: To improve the throughput of a graphic pipeline by shifting a pixel mask by a prescribed number N of bits and selecting N values from new Z values are comparing them with N corresponding Z valves retrieved from a Z buffer and storing smaller values. CONSTITUTION: A Z buffer check instruction simultaneously executes unsigned integer (order number) comparison between a newly calculated distance (Z) value and contents of the Z buffer plural times. The distance of a point to be extracted is compared with a corresponding value in the Z buffer, and then, a proper bit of the pixel mask is set for the purpose of designating a pixel where the point to be extracted is closer (smaller) than the Z buffer value. Preceding calculated bits of the pixel mask are so shifted that continuous Z buffer check instructions accumulate the results in a pixel mask register. In the case of the 16-bit Z value, comparison and pixel mask update are simultaneously executed four times in one instruction cycle. Thus, the throughput of the graphic pipeline is improved.</p> |
