  Vector graphics includes both filled and stroked paths as the main
primitives. While there are many techniques for rendering filled paths on GPU,
stroked paths have proved more elusive. This paper presents a technique for
performing stroke expansion, namely the generation of the outline representing
the stroke of the given input path. Stroke expansion is a global problem, with
challenging constraints on continuity and correctness. Nonetheless, we
implement it using a fully parallel algorithm suitable for execution in a GPU
compute shader, with minimal preprocessing. The output of our method can be
either line or circular arc segments, both of which are well suited to GPU
rendering, and the number of segments is minimal. We introduce several novel
techniques, including an encoding of vector graphics primitives suitable for
parallel processing, and an Euler spiral based method for computing
approximations to parallel curves and evolutes.
