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Apparent Ridges for Line Drawing Tilke Judd1 Fredo Durand1 Edward Adelson1,2

Summary: Apparent Ridges for Line Drawing
Tilke Judd1 FrŽedo Durand1 Edward Adelson1,2
1MIT Computer Science and Artificial Intelligence Laboratory 2 MIT Dept. of Brain and Cognitive Sciences
Shaded View Contours Suggestive Contours Ridges & Valleys Apparent Ridges
Figure 1: The Bust model rendered with several different feature lines. We introduce apparent ridges on the right. They correspond to the
maxima of the normal variation with respect to the viewing plane. Note in particular the left side of the face (to the right) in the suggestive
contour drawing and the nose drawn with ridges and valleys.
Three-dimensional shape can be drawn using a variety of feature
lines, but none of the current definitions alone seem to capture all
visually-relevant lines. We introduce a new definition of feature
lines based on two perceptual observations. First, human percep-
tion is sensitive to the variation of shading, and since shape percep-
tion is little affected by lighting and reflectance modification, we
should focus on normal variation. Second, view-dependent lines
better convey smooth surfaces. From this we define view-dependent
curvature as the variation of the surface normal with respect to a
viewing screen plane, and apparent ridges as the loci of points that
maximize a view-dependent curvature. We present a formal defi-
nition of apparent ridges and an algorithm to render line drawings


Source: Adelson, Edward - Computer Science and Artificial Intelligence Laboratory, Department of Brain and Cognitive Science, Massachusetts Institute of Technology (MIT)


Collections: Biology and Medicine