Synthesis and rendering of seamless and non-repetitive 4D texture variations for measured optical material properties
We have lifted the one weakness of an existing fully automatic acquisition system for spatially varying optical material behavior of real object surfaces. While its expression of spatially varying material behavior with spherical dependence on incoming light as 4D texture (ABTF material model) allows flexible mapping on arbitrary 3D geometries, photo-realistic rendering and interaction in real-time, this very method of texture-like representation exposed it to common problems of texturing, striking in two levels. First, non-seamless textures create visible border artifacts. Second, even a perfectly seamless texture causes repetition artifacts due to side-by-side distribution in large numbers over the 3D surface. We solved both problems through our novel texture synthesis that generates a set of seamless texture variations randomly distributed on the surface at shading time. When compared to regular 2D textures, the inter-dimensional coherence of the 4D ABTF material model poses entirely new challenges to texture synthesis, which includes maintaining the consistency of material behavior throughout the space spanned by the spatial image domain and the angular illumination hemisphere. In addition, we tackle the increased memory consumption caused by the numerous variations through a fitting scheme specifically designed to reconstruct the most prominent effects captured in the material model.
Fellner, Dieter W.