Line Direction Matters: An Argument For The Use Of Principal Directions In 3D Line Drawings
Author(s): Ahna Girshick, Victoria Interrante, Steven Haker, Todd Lemoine.
Proceedings: 1st International Symposium on Non-Photorealistic Animation and Rendering (NPAR'00), pp. 43--52, Annecy, France, June 05 - 07,
2000.
[BibTeX] 
Abstract:
While many factors contribute to shape perception, psychological
research indicates that the direction of lines on the surface may
have an important influence. This is especially the case when
other techniques (shading, silhouetting) do not present sufficient
shape information. The psychology literature suggests that lines
in the principal directions of curvature may communicate surface
shape better than lines in other directions. Moreover, principal
directions have the quality of geometric invariance so line
directions are based on the surface geometry and are viewpoint
and light source independent, and the lines do not move above
over the surface during animation unless desired. In this work
we describe principal direction line drawings which show the
flow of curvature over the surface. The technique is presented for
arbitrary surfaces represented by either 3D volume data or a
polygonal surface mesh. The latter format is common in the field
of computer graphics yet thus far has not been widely used for
principal direction estimation. The methods offered in this paper
can be used alone or in conjunction with other NPR techniques to
improve artistic 3D renderings of arbitrary surfaces.