Abstract
In order to draw a photorealistic surface, Bidirectional Texture Functions(BTFs), a 6D texture function which extends Bidirectional Reflectance Distribution Function(BRDF) to include the self-shadowing, self-occlusion and inter-reflection effects, has been mentioned frequently in recent years. Its main drawback is its massive data size. To solve this, Spatial Bidirectional Reflectance Function (SBRDF) techniques compress BTFs into reflectance model parameters. However, SBRDF cannot produce the self-shadowing and self-occlusion effects in real-world surface geometry. This work is aimed to this drawback. I find how self-shadowing and self-occlusion affect the surface by additional physical-based analysis. And I rely on two physical phenomena to divide self-shadowing and self-occlusion into two independent effects. First, self-shadowing is view independent. Second, self-occlusion is independent of lighting direction changes. After these analyses, I use SBRDF and additional self-shadowing and self-occlusion I found to render a photorealistic surface as non-compressed BTFs doing.