3D rendering using a hemishperical basis

Abstract

Illuminating 3-Dimension objects under a distant environment is a very time-consuming process. Using spherical harmonic (SH) to represent the reflectance property is a technique for reducing the huge number of shading calculations. A study on using the SH basis to represent the reflectance, including the visibility, of surface elements and the lighting environment was carried out. Based on the visual C++ 6.0 platform (OpenGL language) and Cg platform, a hardware shading engine for diffuse surfaces with visibility has been built. In my study, the number of SH coefficients for rendering is varied. The visual result shows that using 25-49 SH coefficients can only simulate a very rough shadow effect. Using 81 SH coefficients can obtain an acceptable shadow effect. Finally, several factors that affect the rendering quality were discussed.