Stencil-then-cover path rendering with shared edges

Abstract

One embodiment of the present invention includes techniques for rasterizing primitives that include edges shared between paths. For each edge, a rasterizer unit selects and applies a sample rule from multiple sample rules. If the edge is shared, then the selected sample rule causes each group of coverage samples associated with a single color sample to be considered as either fully inside or fully outside the edge. Consequently, conflation artifacts caused when the number of coverage samples per pixel exceeds the number of color samples per pixel may be reduced. In prior-art techniques, reducing such conflation artifacts typically involves increasing the number of color samples per pixel to equal the number of coverage samples per pixel. Advantageously, the disclosed techniques enable rendering using algorithms that reduce the ratio of color to coverage samples, thereby decreasing memory consumption and memory bandwidth use, without causing conflation artifacts associated with shared edges.