A Comparison of Global Illumination Methods Using Perceptual Quality Metrics

This work aims to build a comparison basis for analyzing global illumination methods. We have compared six state-of-the-art global illumination methods, ranging from Monte Carlo Path Tracing techniques to Density Estimation methods such as Progressive Photon Mapping, and the mixture approach Vertex Connection and Merging, using nine test scenes with very different characteristics, including many different light types, illumination conditions and BRDFs, exploring many different light scattering events. In order to compare results, the perceptual quality metrics SSIM and HDR-VDP-2 were used. We provide a complete set of convergence rate curves and results for all test scenes and all analyzed methods. We also discuss strategies to generate reference images for each case. We concluded that in general cases the overhead introduced by BPT and VCM is well compensated by the quality of the produced images, however VCM can handle more interesting effects. We also showed there are usual cases such as interiors with strong indirect illumination in which Light Tracing method excels.