8

How Radiosity Works in 3ds Max 55
from fast, interactive lighting studies to images of
exceptional quality and realism .
See also
How Radiosity Works in 3ds Max (page 3–55)
Radiosity Workflows (page 3–56)
Animation with Radiosity (page 3–59)
Radiosity Cont rols (page 3–60)
Lighting Analysis (page 3–75)
Lighting Analysis Dialog (page 3–75)
Advanced Lighting Override Material (page
2–1410)
How R a diosity Work s in 3ds M ax
This is an overview of how radiosity works in
3ds Max:
1. Object by object, 3ds Max loads a copy of the
scene into the radiosity engine.
2. 3ds Max subdivides each object according to
the Global Subdivision Settings in the Radiosity
Meshing Parameters rollout, or according to the
object’s individual object properties, if those
differ from the global settings.
3. 3ds Max emits a cert ain 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,” f or a more detailed description of the
solution process.
R efi nement S teps for R a dios it y
Theradiosityprocessinvolvesthreestagesof
increasing refinement. The first t wo stages occur
during the primary radiosity processing, and the
thirdstagecanbeusedduringthefinalrendering.
Within each of the first two stages, you can stop
and star t 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 solutio n are Initial Q uality, Refine,
and then Regathering.
1. Initial Quality
In the Initial Quality stage, the distribution
of diffuse lighting in the scene is calculate d
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