Verification of Physically Based Rendering Algorithms

Within computer graphics, the field of predictive rendering is concerned with those methods of image synthesis that yield results that do not only look real, but are also radiometrically correct renditions of nature, i.e. which are accurate predictions of what a real scene would look like under given lighting conditions. In order to guarantee the correctness of the results obtained by such techniques, three stages of such a rendering system have to be verified with particular care: the light reflection models, the light transport simulation and the perceptually based calculations used at display time. In this report, we will concentrate on the state of the art with respect to the second step in this chain. Various approaches for experimental verification of the implementation of a physically based rendering system have been proposed so far. However, the problem of proving that the results are correct is not fully solved yet, and no standardized methodology is available.We give an overview of existing literature, discuss the strengths and weaknesses of the described methods and illustrate the unsolved problems. We also briefly discuss the related issue of image quality metrics.