| 摘要 |
A method and system are provided for performing rasterisation of input primitives to generate graphics fragments to be subsequently processed to generate output data for display in a render output area. The method comprises, for each input primitive, determining from the vertex data of the primitive a bounding box for the primitive, and performing a multi-level patch analysis in order to determine patches covered at least partially by the primitive, at a first level the render output area being divided into one or more patches, and at each subsequent level the render output area being divided into a plurality of patches smaller than the patches of the preceding level. Each patch has an array of grid points defining boundaries of a set of sub-patches within that patch, and at each level the patch analysis, for each selected patch at that level, performs as a default operation testing of the grid points of the selected patch against each edge equation of the primitive to determine whether the primitive at least partially covers any of the sub-patches. If the primitive at least partially covers any of the sub-patches of the selected patch, and assuming the final level of the patch analysis has not been reached, that selected patch is sub-divided into the set of sub-patches, and for each sub-patch that the primitive at least partially covers, that sub-patch is treated as a selected patch to be analysed at the next level of the patch analysis. One or more graphics fragments are then generated for at least each sub-patch of the final level of the patch analysis determined to be covered at least partially by the primitive. When performing patch analysis of a selected patch, a bounding box evaluation step determines if a special condition exists where the bounding box does not cover any of the grid points in the array of grid points, or if a special grid point coverage condition exists, and, in the presence of such a special condition, an alternative operation for that selected patch is adopted instead of the default operation, the alternative operation determining whether the primitive at least partially covers any of the sub-patches of the selected patch without testing the grid points of the selected patch against the at least one edge equation of the primitive. By avoiding the need to test the grid points against each edge equation in such a situation, significant performance improvements can be realised. |
