Reconstructing illumination functions with selected discontinuities.

Third Eurographics Workshop on Rendering, pages 99--112, May 1992.

Typical illumination functions contain boundaries that are discontinuous in intensity or derivative. These discontinuities arise from contact between surfaces, and from the penumbra and umbra boundaries of shadows cast by area light sources. In this paper, we present an algorithm that allows for smooth (C1) reconstruction of intensity everywhere across a surface except along selected edges of intensity or derivative discontinuity. The reconstruction algorithm is based on a piecewise-cubic scattered data interpolation method originally proposed by Clough and Tocher. Our results show marked improvement over piecewise linear or C1 quadratic reconstructions of some simple illumination functions.

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