Contents Introduction Overview of Deterministic algorithm Overview of Monte Carlo algorithm Scenes used for comparison Accuracy analysis Results obtained Conclusion Acknowledgments |
The task of global illumination algorithm is to solve the well known so called "Rendering equation" [Kaj86]. The equation describes light energy transfer in a very general situation.
TBT does not solve it in full generality. Our model of light-surface interaction accounts for:
It should be mentioned, however, that specular refraction is taken into account at the final stage (when a view-dependent image is generated by means of backward ray tracing). Thus, the global illumination algorithm (deterministic) does not account for light refraction (it assumes that light rays pass through transparent materials without change of direction); this is clearly seen in Figure 1a.
Our method of solving the rendering equation belongs to a group of progressive radiosity methods [CCWG88]. It is characterized by the following features:
A more detailed discussion of the TBT deterministic global illumination algorithm and some of its extensions can be found in [MK94].
The result of global illumination analysis describes illuminance distribution in the scene. These data are kept in the form of the so called illumination maps (i-maps). During solution we assume uniform luminance / illuminance of each triangular patch. However, in i-maps (for better looking images) illuminance of each triangle is considered as linearly changing and continuous between adjacent triangles. Necessary recalculation (it is a sort of filtering) is done at the final stage of the global illumination algorithm.
Illumination maps can be later used to generate an accurate image by means of backward ray tracing. During this process DIRECT illumination of each visible point (that is illumination by light going directly from light sources, without intermediate diffuse scattering) is computed explicitly without use of i-maps while only indirect component of illumination is extracted from i-maps (i-maps in TBT keep thedirect and indirect components of illuminance separately). In this way we provide an accurate account for the direct illuminance (in many cases it is absolutely precise).
The direct component of illumination maps is also used in TBT in cases when we need fast display of images with no use of backward ray tracing (for real-time animation, say).
Contents Introduction Overview of Deterministic algorithm Overview of Monte Carlo algorithm Scenes used for comparison Accuracy analysis Results obtained Conclusion Acknowledgments |
Copyright 1996 Andrei Khodulev. | [Home] |