Calculation of plane equations after determination of Z-buffer visibility

摘要

One embodiment of the present invention sets forth a technique for computing plane equations for primitive shading after non-visible pixels are removed by z culling operations and pixel coverage has been determined. The z plane equations are computed before the plane equations for non-z primitive attributes are computed. The z plane equations are then used to perform screen-space z culling of primitives during and following rasterization. Culling of primitives is also performed based on pixel sample coverage. Consequently, primitives that have visible pixels after z culling operations reach the primitive shading unit. The non-z plane equations are only computed for geometry that is visible after the z culling operations. The primitive shading unit does not need to fetch vertex attributes from memory and does not need to compute non-z plane equations for the culled primitives.