BTF Rendering for Virtual Environments

Virtual Environments mostly try to convey as realistic as possible impressions. Among other senses, the eye provides the users with the most important inputs. Achieving visual realism typically relies on highly accurate geometric models. Unfortunately unhandleable amounts of triangles need to be rendered to adequately represent mesostructure. Furthermore, sophisticated lighting calculations need to be computed to incorporate local self-shadowing and interreflection effects. In current VR systems material representations like textures and bump-maps are utilized to compensate the abovementioned problems. While these approximations yield sufficient results for very simple materials, they are insufficient for more ambitious applications like cloth visualization or interior design, which require highly realistic material representations like the bi-directional texture function (BTF). In this work, we compare several real-time BTF rendering methods concerning accuracy, runtime and memory requirements, and identify application areas for the different techniques. In addition, we show how BTF rendering can be integrated into scene-graph systems.