9

56 Chapter 17: Rendering
from fast, interactive lighting studies to images of
exceptional quality and realism.
See also
How Radiosity Works in 3ds Max (page 3–56)
Radiosity Workflows (page 3–57)
Animation with Radiosity (page 3–60)
Radiosit y Controls (page 3–61)
Lighting Analysis (page 3–76)
Advanced Lighting Override Material (page
2–1601)
How R a diosity Wor k s in 3ds M ax
This is an overview of how radiosity works in
3ds Max:
1. Object by object, 3 ds Max lo ads a copy of the
scene i nto the radiosity engine.
2. 3ds Max subdivides each object according to
the Global Subdiv ision Sett ings in the Radiosity
Meshing Parameters rollout, or according to the
object’s individual object prop erties, if those
differ from the global sett ings.
3. 3ds Max emits a certain amount of rays, based
on the average scene reflectance and number of
polygons. The brightest light source will have
more r ays to emit than the weakest light source.
4. Theseraysbouncearoundrandomlyinthe
scene and deposit energy on the faces.
5. 3dsMaxupdatestheviewportsbytakingallthe
energy from the faces and spreading it to the
closest vertex.
See the section that follows, “ Refinement Steps for
Radiosity,” for a more detailed description of the
solution process.
R efi nement Steps for Ra dios it y
Theradiosityprocessinvolvesthreestagesof
increasing refinement. The first two stages occur
during the primary radiosity processing, and the
thirdstagecanbeusedduringthefinalrendering.
Within each of t he first two stages, you c an stop
and start the processing at any time. This can be
useful for evaluating interim results or increasing
the level of accuracy you desire. For example,
you can interrupt the Initial Quality stage at
50%andjumpaheadtotheRefinestageifyou
wish. However, once you enter the Refine stage,
you cannot continue further iterations of Initial
Qualit y unless you restart the solution.
The stages of a radiosity solution are Initial Quality, Refine, and
then Regathering.
1. Initial Quality
In the Initial Qualit y stage, the distribution
of diffuse lighting in the scene is ca lculated
by essentially mimicking the behavior of
real photons. Rather than tracing the path
of an essentially infinite number of photons,
statistical methods are used to choose a much
smaller set of “photon rays” whose distribution
in space is represent ative of the actual