Pierre Benard, Aaron Hertzmann, Michael Kass
Abstract:
This paper introduces a method for accurately computing the visible
contours of a smooth 3D surface for stylization. This is a
surprisingly difficult problem, and previous methods are prone to
topological errors, such as gaps in the outline. Our approach is to
generate, for each viewpoint, a new triangle mesh with contours that
are topologically-equivalent and geometrically close to those of the
original smooth surface. The contours of the mesh can then be rendered
with exact visibility. The core of the approach is Contour-Consistency,
a way to prove topological equivalence between the
contours of two surfaces. Producing a surface tessellation that
satisfies this property is itself challenging; to this end, we
introduce a type of triangle that ensures consistency at the
contour. We then introduce an iterative mesh generation procedure,
based on these ideas. This procedure does not fully guarantee
consistency, but errors are not noticeable in our experiments. Our
algorithm can operate on any smooth input surface representation; we
use Catmull-Clark subdivision surfaces in our implementation. We
demonstrate results computing contours of complex 3D objects, on which
our method eliminates the contour artifacts of other methods.
Paper (PDF)
To appear in ACM Transactions on Graphics