Spherical Harmonic Lighting of Wavelength-Dependent Phenomena

Abstract

Rendering of objects that exhibit iridescence has previously been limited to simple lighting conditions generated from a few point or directional lights. We extend this idea by modeling light interference as a Bidirectional Re- flectance Distribution Function (BRDF) and precomputing the physically based surface response to hemisphere lighting in terms of a low order spherical harmonic basis. Parameterizing by view direction, we can store the light interference effect in a 2D texture map, where each entry contains a vector of spherical harmonic basis function coefficients. Our technique achieves a full spectral representation of interference color by maintaining the spherical harmonic basis in terms of Spectral Power Distribution (SPD) instead of a color-based format such as RGB. In addition, we demonstrate that our approach is amenable to current graphics hardware and can render at real-time frame rates.