Simulation of Low Frequency Lighting Environments Using Irradiance Volumes Based on Unstructured Grids

In the field of computer graphics, the problem of generating realistic images of virtual environments has been studied extensively. One important factor determining the realism of such images is how the interaction between light and an environment is simulated. The focus of this thesis is on the real time simulation of diffusely reflecting dynamic objects in static lighting environments. The simulation is performed using irradiance volumes, which are structures containing a set of irradiance distribution samples taken throughout the simulation space, along with functionality to interpolate between these samples. Irradiance volumes based on unstructured grids in the form of Delaunay triangulations are studied and efficient point location and interpolation methods are described. The use of this kind of unstructured grids allows for irradiance samples taken in practically arbitrary positions. In the irradiance volumes studied in this thesis, the irradiance distribution samples are represented as approximations expressed as linear combinations of spherical basis functions. Basis function sets of spherical harmonics and spherical radial basis functions are compared in terms of approximation accuracy and storage efficiency.