TAPESTRY: The Art of Representation and Abstraction
Photon Mapping
DEFINITION
Photon Mapping refers to the use of photon maps in rendering. A photon map is a data structure that stores the location, direction and intensity of an incident ray or photon of light. They are created by randomly casting a number of rays from a light source, distributed according to the characteristics of the source. As each ray encounters a reflective or refractive surface, a record is kept of the condition of impact (an entry in the photon map) and the ray is then bounced further into the scene.
EXPLANATION
The surfaces we see in a scene are illuminated by a complex combination of direct illumination (straight from a lamp to the surface) and light reflected from one surface to another (indirect illumination). This is the "Global Illumination" problem and photonmaps are one part of the solution.
FURTHER READING
There is a good general discussion of Global Illumination, including photon maps at http://web.cs.wpi.edu/. Take a look if you're interested.
Last updated: April, 2014
