Rendering Inhomogeneous Surfaces with Radiosity

Abstract

Natural surfaces are often complex: they nearly always exhibit small scale imperfections such as dirt, dust, cracks, etc., as well as large scale structural elements, as for wickerwork, brick walls, textiles, pebbles, etc., that are generally too complex to be modeled explicitly. In this paper, we propose a new multi-scale periodic texture model adapted to the efficient simulation of the previously mentioned features. This new model combines notions of virtual ray tracing (that we have recently introduced) with bi-directional texture function, while it also considers self-shadowing and inter-reflections at texture scale. In a second step, the texture model is integrated into hierarchical radiosity with clustering. Therefore, an extension of radiosity techniques, currently limited to texture maps, bump maps and general (homogeneous) reflectance functions, is proposed. The final rendering consists of applying a second ray tracing pass, based on a gathering methodology adapted to the model. The method provides images at a significant lower computation and memory consumption cost than with explicit models in the case of periodic features (wickerwork, grids, pavements, etc.) for a similar visual quality.