Apparent Ridges for Line Drawings

Abstract

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 perception is sensitive to the variation of shading, and since shape perception 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 definition of apparent ridges and an algorithm to render line drawings of 3D meshes. We show that our apparent ridges encompass or enhance aspects of several other feature lines.

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Acknowledgments

This work was supported by a NSF CAREER award 0447561 and Grant No. 0429739. Frédo Durand acknowledges a Microsoft Research New Faculty Fellowship and a Sloan Fellowship. Tilke Judd was supported by an NSF graduate fellowship. We thank Rusinkiewicz and DeCarlo for their rtsc software. We thank Yann LeTallec, MIT pre-reviewers and especially the SIGGRAPH reviewers for their extensive and insightful feedback on this work.