Caustics and specular reflection models for spherical objects and lenses

Abstract

Ray tracing is a most powerful and elegant rendering technique and is able to render shadows, reflections, and refractions very nicely. However, reflections and refractions in ray tracing simulate the reflected and refracted “eye” ray and not the “light” ray. Standard ray tracing techniques therefore suffer from a lack of specular interreflection and caustics. This paper proposes an algorithm to render reflected and refracted “light” rays for spherical objects and lenses. Indirect illumination is a result of the reflection of light rays. Reflected light may be considered an additional light source; if it is included in the intensity calculation, indirect illumination can be rendered. The refracted light is noticeable as a focal point for a convex lens, and as dispersed light in a concave lens. The dispersed light has low intensity which may be insignificant for the illumination calculations. In the case of a convex lens, light rays become extremely directional and light energy increases. The result appears as caustics. The proposed algorithm is limited to a collimated light ray and does not account for the case of dispersed light.