Transparency can be a useful device for simultaneously depicting multiple superimposed layers of information in a single image. However, in computer-generated pictures -as in photographs and in directly viewed actual objects -- it can often be difficult to adequately perceive the threedimensional shape of a layered transparent surface or its relative depth distance from underlying structures. Inspired by artists' use of line to show shape, we have explored methods for automatically defining a distributed set of opaque surface markings that intend to portray the three-dimensional shape and relative depth of a smoothly curving layered transparent surface in an intuitively meaningful (and minimally occluding) way. This paper describes the perceptual motivation, artistic inspiration and practical implementation of an algorithm for "texturing" a transparent surface with uniformly distributed opaque short strokes, locally oriented in the direction of greatest normal curvature...
Victoria Interrante, Henry Fuchs, Stephen M. Pizer