Abstract

Water is a surface that is visually distinctive. What properties of the image allow us to make this unique inference? To answer this question, we have rendered water using computer graphics. There are three parts to the model: the reflectance function, the surface waveform, and the dynamics of the moving waves. The reflectance function is unique because Fresnel reflection dominates with essentially no reflection at normal incidence. The surface waveform is unusual in that it is sinusoidal at low amplitude, with an ~30° spectrum of orientation. The dynamics are currently under study. To make the inference water solely from the reflectance function requires proof from the image data that only the Fresnel term is relevant for the patch of surface under view. Some minimal conditions which permit such an inference are presented. One condition is hemispheric illumination such as the sky.

© 1985 Optical Society of America