Scalable Spherical Harmonics Hierarchies

Scalable Spherical Harmonics Hierarchies (SSPHH) is a real-time rendering solution to the global illumination problem. Our novel method is a system of components that enables the computation of light probes and the conversion to spherical harmonics coefficients, which are used as anisotropic time-varying light sources we call Spherical Harmonics Lights (SPHLs). The SPHLs encode irradiance information that can be used for imagebased lighting. Our approach focuses on reconstructing scene lighting using diffuse illumination but is flexible to allow specular details. Furthermore, we consider the light transport from neighboring SPHLs by computing a transfer coefficient that estimates how much light from one probe is visible at another. SPHLs can be used for physically-based lighting using rendering methods similar to point lights and shadow maps. We created a reproducible testing methodology to compare our images with those of a commercial path tracer by automatically generating the appropriate scene information which gets used with absolute error metrics to determine remaining image defects. Our SSPHH method utilizes a scalable architecture to distribute the rendering of light probes between client and worker nodes using the ZeroMQ Majordomo protocol