Preserving Realism in real-time Rendering of Bidirectional Texture Functions

The Bidirectional Texture Function (BTF) is a suitable representation for the appearance of highly detailed surface structures under varying illumination and viewing conditions. Since real-time rendering of the full BTF data is currently not feasible, approximations of the six-dimensional BTF are used such that the amount of data is reduced and current graphics hardware can be exploited. While existing methods work well for materials with low depth variation, realism is lost if the depth variation grows. In this paper we analyze this problem and devise a new real-time rendering method, which provides significant improvements with respect to realism for such highly structured materials without sacrificing the general applicability and speed of previous algorithms. We combine our approach with texture synthesis methods to drastically reduce the texture memory requirements and demonstrate the capabilities of our new rendering method with several examples.