Light mesh: soft shadows as interpolation of visibility

摘要

The light meshes (LM) method is a modification of the recursive ray tracing algorithm (RRTA). In this paper we consider an original procedure of shadow calculations, which allows soft shadows to be obtained. The light meshes method can be integrated easily into existing implementations of RRTA as a supplementary technique or plug-ins. In comparison with conventional RRTA the suggested technique allows us to: (a) build soft shadows, (b) speed up a process of shadow calculations, (c) simulate main effects of diffuse interreflections, (d) omit the ambient term. Obviously, visual results of the LM method differ slightly from those calculated with the help of the basic RRTA.A light mesh is a point set in the 3D space of a scene. In practice, it is approximated by a finite set of points, as a rule, by evenly spaced grids. At each mesh point we compute illuminance, which characterizes some kind of "light field intensity" in the scene space. Then an important part of resulting illumination of a scene object point is obtained by the interpolation of the stored values of nearby mesh points.Experiments show that the approach proposed reduces computational time with respect to the ray tracing algorithm if a scene contains a lot of light sources and/or an image has a large resolution. (C) 2004 Elsevier B.V. All rights reserved.