What is "radiosity"

n. (cx computer graphics English) A three-dimensional rendering system that simulates all reflections from objects in the scene.

In 3D computer graphics, radiosity is an application of the finite element method to solving the rendering equation for scenes with surfaces that reflect light diffusely. Unlike rendering methods that use Monte Carlo algorithms (such as path tracing), which handle all types of light paths, typical radiosity only account for paths (represented by the code "LD*E") which leave a light source and are reflected diffusely some number of times (possibly zero) before hitting the eye. Radiosity is a global illumination algorithm in the sense that the illumination arriving on a surface comes not just directly from the light sources, but also from other surfaces reflecting light. Radiosity is viewpoint independent, which increases the calculations involved, but makes them useful for all viewpoints.

Radiosity methods were first developed in about 1950 in the engineering field of heat transfer. They were later refined specifically for the problem of rendering computer graphics in 1984 by researchers at Cornell University and Hiroshima University.

Notable commercial radiosity engines are Enlighten by Geomerics (used for games including Battlefield 3 and Need for Speed: The Run); 3ds Max; form•Z; LightWave 3D and the Electric Image Animation System.

In radiometry, radiosity is the radiant flux leaving (emitted, reflected and transmitted by) a surface per unit area, and spectral radiosity is the radiosity of a surface per unit frequency or wavelength, depending on whether the spectrum is taken as a function of frequency or of wavelength. The SI unit of radiosity is the watt per square metre , while that of spectral radiosity in frequency is the watt per square metre per hertz (W·m·Hz) and that of spectral radiosity in wavelength is the watt per square metre per metre (W·m)—commonly the watt per square metre per nanometre . The CGS unit erg per square centimeter per second is often used in astronomy. Radiosity is often called "intensity" in branches of physics other than radiometry, but in radiometry this usage leads to confusion with radiant intensity.

Radiosity may refer to:

• Radiosity (radiometry), the total radiation (emitted plus reflected) leaving a surface
• Radiosity (computer graphics), a rendering algorithm which gives a realistic rendering of shadows and diffuse light