GPU-friendly Stroke Expansion

TL;DR

This paper introduces a GPU-optimized, fully parallel technique for stroke expansion in vector graphics, enabling efficient rendering of stroked paths with minimal segments and high continuity.

Contribution

It presents a novel GPU-friendly algorithm for stroke expansion that handles complex constraints and produces minimal, well-suited segments for rendering.

Findings

Efficient GPU implementation of stroke expansion

Minimal segment output suitable for GPU rendering

Novel encoding and Euler spiral techniques for parallel processing

Abstract

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.