Abstract: Lines drawn over or in place of shaded 3D models can often provide greater comprehensibility and stylistic freedom that shading alone. A substantial challenge for making stylized line drawings from 3D models is the visibility computation. Current algorithms for computing line visibility in models of moderate complexity are either too slow for interactive rendering, or too brittle for coherent animation. We present a method that exploits graphics hardware to provide fast and robust line visibility. Rendering speed for our system is usually within a factor of two of an optimized rendering pipeline using conventional lines, and our system provides much higher visual quality and flexibility for stylization.