light source and make multiple diffuse bounces before reaching the eye. Although there are several approaches to integrating other illumination effects such as specular and glossy reflections, radiosity-based methods are generally not used to solve the complete rendering equation. Basic radiosity also has trouble resolving sudden changes in visibility (e.g. hard-edged shadows) because coarse, regular discretization into piecewise constant elements corresponds to a low-pass box filter of the spatial domain. Discontinuity meshing uses knowledge of visibility events to generate a more intelligent discretization. Confusion about terminology Radiosity was perhaps the first rendering algorithm in widespread use which accounted for diffuse indirect lighting. Earlier rendering algorithms, such as Whitted-style ray tracing were capable of computing effects such as reflections, refractions, and shadows, but despite being highly global phenomena, these effects were not commonly referred to as "global illumination." As a consequence, the terms "diffuse interreflection" and "radiosity" both became confused with "global illumination" in popular parlance. However, the three are distinct concepts. The radiosity method, in the context of computer graphics, derives from (and is fundamentally the same as) the radiosity method in heat transfer. In this context, radiosity is the total radiative flux (both reflected and re-radiated) leaving a surface; this is also sometimes known as radiant exitance. Calculation of radiosity, rather than surface temperatures, is a key aspect of the radiosity method that permits linear matrix methods to be applied to the problem. See also Photon Mapping Ray tracing Path tracing References Further reading Radiosity Overview, from HyperGraph of SIGGRAPH (provides full matrix radiosity algorithm and progressive radiosity algorithm) Radiosity, by Hugo Elias (also provides a general overview of lighting algorithms, along with programming examples) Radiosity, by Allen Martin (a slightly more mathematical explanation of radiosity) ROVER, by Dr. Tralvex Yeap (Radiosity Abstracts & Bibliography Library) Radiosity: Basic Implementations (Basic radiosity survey) External links RADical, by Parag Chaudhuri (an implementation of shooting & sorting variant of progressive radiosity algorithm with OpenGL acceleration, extending from GLUTRAD by Colbeck) Radiosity Renderer and Visualizer (simple implementation of radiosity renderer based on OpenGL) Enlighten (Licensed software code that provides realtime radiosity for computer game applications. Developed by the UK company Geomerics) Global illumination algorithms Heat transfer 3D computer graphics Finite element method