A Technique to Evaluate Irradiance Environment Maps
基于图形硬件的辐照度环境纹理图的计算方法

Irradiance environmental maps are an effective technique to render diffuse objects in arbitrary lighting environments. Based on current computer graphics hardware a technique is proposed for calculating irradiance environmental maps using vertex shader. The approach starts from an analysis of spherical harmonics and finds out a quadratic polynomial form of environment mapping. Using vertex shader instructions the polynomial coefficients and spherical harmonics functions can be fast calculated, and then the corresponding irradiance environment maps are also generated. When the lighting environment changes, the lighting coefficients are fast computed by generating a mipmap of the source environment map, so that real-time recalculating irradiance environment is obtained. The experimental result shows it not only renders realistic lighting but also satisfies the interactive requirements in dynamic lighting environments.