2008

Photon Map
A photon map
™
is a technique to generate the indirect illumination effects
of
caustics on page 6066 and global illumination on page 6072 when you render
with the
mental ray renderer on page 6039 . When it calculates indirect
illumination, the mental ray renderer traces photons emitted from a light.
The photon is traced through the scene, being reflected or transmitted by
objects, until it strikes a diffuse surface. When it strikes a surface, the photon
is stored in the photon map.
Generating photon maps is time-consuming. To improve performance, you
must explicitly specify:
■ Which lights emit photons for indirect illumination.
■ Which objects can generate caustics or global illumination.
■ Which objects can receive caustics or global illumination.
The settings for generating and receiving caustics are on the Object Properties
dialog >
mental ray Panel on page 262 .
The photon map stores photons only for objects that can receive caustics,
global illumination, or both.
To further reduce the time required to generate a photon map, photons are
limited by the Trace Depth controls. These limit the number of times a photon
can be reflected, refracted, or both.
In animations, another way to save time is to reuse the photon-map file. If
lighting doesn't change over the course of an animation, use the
Photon Map
controls
on page 6102 .
The mental ray renderer saves photon maps as
PMAP files on page 7897 . Photon
map controls are on the Render Scene Dialog > Indirect Illumination panel >
Caustics And Global Illumination rollout on page 6096 .
PHY Files
You can save
Physique on page 4522 data to a Physique (PHY) file. This saves
data common to all objects that share a given Physique modifier.
Later, you can reload the PHY file, either to restore the data that belongs to a
particular skin or portion of skin, or to transfer the Physique of one skin (or
portion of it) to a different one.
7894 | Glossary