The Render Manager > mental ray (Global Renderer)
The Render Manager > (expand a pass) > mental ray
Set the current pass and choose Render > Render > Renderer Options from the Render toolbar.
Tab: Importons [Properties Reference]
The Photon Map is essentially a table that stores the positions of the photons in the scenes along with their RGB energy levels for each of the thousands of photons.
When mental ray wants to determine how the Photon Map affects a given point in space, the raytracer consults the Photon Map to determine which photons are nearby (within a given radius) and then calculates the photon contribution to the total lighting in the scene, based on the energy level of every photon within the radius. Only one map is created regardless of the number of lights.
The path of photons that occurs when using caustic illumination.
Both scenes below have the same number of lights and types of shaders.
This scene does not use caustic effects.
This scene uses caustic effects. Notice the reflections on the table caused by the glass pencil holder. Both the reflectivity and refraction of the glass play a part in how the caustic effects are rendered.
Specifying the Photon Map File
You can also specify a Photon Map in the Photon Map text box. Click the browse (...) button to open a browser and select a map file.
To modify the display of caustics in the region, you can generate a map of the caustic effect by selecting the Rebuild option (wait while the Photon Map is calculated and displayed). You can then zoom, pan, or play back your animation in the render region using the precomputed map of the caustics instead of computing the caustic effect each time the region is refreshed, which takes much longer.
