Shading models for linear and area light sources

Abstract

Two shading models that account for, respectively, both diffuse reflection and specular reflection caused by ideal diffuse linear light sources and ideal diffuse polygonal light sources are proposed. In both models, the diffuse reflection component is accurately represented in an analytic form, while the specular reflection component is represented by an integration taking Phong's specular model as the kernel. For linear light sources, a precise recursive formula is derived to calculate the specular reflection component analytically. For polygonal light sources, we adopt Taylor's series to approximate the integration. All the analytic representations of both diffuse and specular terms involve no complex coordinate transformation and the images generated by the shading models are very realistic. Finally, a shadow detection algorithm is presented for the polygonal environment, the precise umbra and penumbra can be produced. Results show great potential of our method.