For thirty years, resolution-independent 2D standards (e.g. PostScript, SVG) have depended on CPU-based algorithms for the filling and stroking of paths. Advances in graphics hardware have largely ignored accelerating resolution-independent 2D graphics rendered from paths. We introduce a two-step “Stencil, then Cover” (StC) programming interface. Our GPU-based approach builds upon existing techniques for curve rendering using the stencil buffer, but we explicitly decouple in our programming interface the stencil step to determine a path’s filled or stroked coverage from the subsequent cover step to rasterize conservative geometry intended to test and reset the coverage determinations of the first step while shading color samples within the path. Our goals are completeness, correctness, quality, and performance—yet we go further to unify path rendering with OpenGL’s established 3D and shading pipeline. We have built and productized our approach to accelerate path rendering as an OpenGL extension.
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