ABSTRACT
In the rendering equation, light sources produce their effect when we factor in the emissive component of a surface. In real-time graphics, doing this “properly” with emissive surfaces is usually a luxury we cannot afford. Even in offline situations where it can be afforded, we might have reasons to just emit light out of nowhere, to make it easier to get control of the look of the scene for dramatic lighting, or to simulate the light that would be reflecting from a surface for which we are not wasting time to model geometry since it is off camera. Thus, we usually have light sources that are abstract entities within the rendering framework with no surface geometry to call their own. This entry discusses some of the most common types of light sources.
