Issue No. 02 - March/April (2008 vol. 14)
The apparent reflectance of a surface depends upon the resolution at which it is imaged. Conventional reflectance models represent reflection at a single predetermined resolution; however, a low-resolution pixel that views a greater surface area often exhibits a reflectance more complicated than a high-resolution pixel with a smaller area. To address resolution dependency in reflectance, we utilize a generalized reflectance model based on a mixture of multiple conventional models, and present a framework for efficiently determining the reflectance mixture model of each pixel with respect to resolution. Mixture model parameters are precomputed at multiple resolutions and stored in mipmaps. Unlike color textures, these reflectance parameters cannot be accurately filtered by trilinear interpolation, so we present a technique for nonlinear mipmap filtering that minimizes aliasing in rendered results. This framework can be applied with various parametric reflectance models in graphics hardware for real-time processing. With this technique for filtering and rendering with mipmaps of reflectance mixture models, our system can rapidly render the resolution-dependent reflectance effects that are customarily disregarded in conventional rendering methods. At the end of this paper, we also describe how shadowing and masking effects can be incorporated into this framework to increase the realism of rendering.
Antialiasing, Color, Shading, shadowing, and texture, Reflectance
Ping Tan, Stephen Lin, Long Quan, Baining Guo, Harry Shum, "Filtering and Rendering of Resolution-Dependent Reflectance Models", IEEE Transactions on Visualization & Computer Graphics, vol. 14, no. , pp. 412-425, March/April 2008, doi:10.1109/TVCG.2007.70439