A low-complexity discrete radiosity method

Abstract

Rather than using Monte Carlo sampling techniques or patch projections to compute radiosity, it is possible to use a discretization of a scene into voxels and perform some discrete geometry calculus to quickly compute visibility information. In such a framework , the radiosity method may be as precise as a patch-based radiosity using hemicube computation for form-factors, but it lowers the overall theoretical complexity to an O(N log N) + O(N), where the O(N) is largely dominant in practice. Hence, the apparent complexity is linear for time and space, with respect to the number of voxels in the scene. This method does not require the storage of pre-computed form factors, since they are computed on the fly in an efficient way. The algorithm which is described does not use 3D discrete line traversal and is not similar to simple ray-tracing. In the present form, the voxel-based radiosity equation assumes the ideal diffuse case and uses solid angles similarly to the hemicube.

Interactive Volume-Based Indirect Illumination of Dynamic Scenes

“…Radiosity based methods in voxel space have addressed the illumination problem, like Greger et al [6] and Chatelier et al [1] but their results were not computed in real-time and had large storage requirements. Modern advances of the same approach, Kaplanyan [9], yielded much faster results than before, but ignored indirect occlusion and secondary light bounces.…”

Cached Multi-Bounce Solution and Reconstruction for Voxel-Based Global Illumination

“…In (Chatelier and Malgouyres, 2006), a new global illumination approach is considered, with a cost which is linear with respect to the number of visibility rays. This is a promising result, but there are shortcomings.…”

“…In (Malgouyres, 2002) and (Chatelier and Malgouyres, 2006), a new to global illumination and a discretization of the diffuse illumination, based on voxel approximation of surfaces by voxels is proposed. The interest of the method is that visibility is determined in linear time with respect to the number of rays.…”

“…Moreover, it directly provides a voxel-based irradiance lookup octree. However, the method presented in (Chatelier and Malgouyres, 2006) has two weaknesses: first, solid angle sampling is the same for each bounce, and in particular, direction sampling from light sources is insufficient while the cost of direction sampling after one or two bounces is very expensive. Second, no reconstruction process is presented and direct display of the voxel solution requires many voxels, which also increases the runtime.…”

“…In section 2, we have presented previous work and outline the method of (Chatelier and Malgouyres, 2006). In Section 3, we present the iterated cached global illumination method, and in Section 4, we explain our reconstruction process.…”