Editing Photon mapping (section)

==Effects==

===Caustics===
[[File:Glas-1000-enery.jpg|thumb|A model of a wine glass [[ray tracing (graphics)|ray-traced]] with photon mapping to show [[Caustic (optics)|caustics]]]]
Light [[Refraction|refracted]] or [[specular reflection|reflected]] causes patterns called [[Caustic (optics)|caustics]], usually visible as concentrated patches of light on nearby surfaces. For example, as light rays pass through a wine glass sitting on a table, they are refracted and patterns of light are visible on the table. Photon mapping can trace the paths of individual photons to model where these concentrated patches of light will appear.

===Diffuse interreflection===

[[Diffuse interreflection]] is apparent when light from one diffuse object is reflected onto another.  Photon mapping is particularly adept at handling this effect because the algorithm reflects photons from one surface to another based on that surface's [[bidirectional reflectance distribution function]] (BRDF), and thus light from one object striking another is a natural result of the method.  Diffuse interreflection was first modeled using [[Radiosity (computer graphics)|radiosity]] solutions.  Photon mapping differs though in that it separates the light transport from the nature of the geometry in the scene.  [[Color bleeding (computer graphics)|Color bleed]] is an example of diffuse interreflection.

===Subsurface scattering===

[[Subsurface scattering]] is the effect evident when light enters a material and is scattered before being absorbed or reflected in a different direction.  Subsurface scattering can accurately be modeled using photon mapping.  This was the original way Jensen implemented it; however, the method becomes slow for highly scattering materials, and [[bidirectional surface scattering reflectance distribution function]]s (BSSRDFs) are more efficient in these situations.