  This paper proposes a method for computing the visible occluding contours of
subdivision surfaces. The paper first introduces new theory for contour
visibility of smooth surfaces. Necessary and sufficient conditions are
introduced for when a sampled occluding contour is valid, that is, when it may
be assigned consistent visibility. Previous methods do not guarantee these
conditions, which helps explain why smooth contour visibility has been such a
challenging problem in the past. The paper then proposes an algorithm that,
given a subdivision surface, finds sampled contours satisfying these
conditions, and then generates a new triangle mesh matching the given occluding
contours. The contours of the output triangle mesh may then be rendered with
standard non-photorealistic rendering algorithms, using the mesh for visibility
computation. The method can be applied to any triangle mesh, by treating it as
the base mesh of a subdivision surface.
