8

64 Chapter 17: Rendering
Once the f ull Initial Qualit y percentage has b een
reached, clicking Continue has no effect.
Stop—Stops the radiosity processing. The Start
menu changes to Continue. You can later click
Continue to resume radiosity processing, as
described for the Start menu.
Keyboard shortcut: ESC
Process group
The options in this group set the behavior of the
first two stages of the radiosity solution, Initial
Quality and Refine.
Initial Quality—Sets the quality percentage at
which to stop the Initial Quality stage, up to
100%. For example, if you specify 80%, you will
get a radiosity solution that is 80% accurate in
energy distribution. A goal of 80 to 85% is usually
sufficient for good results.
During the Initial Quality stage, the radiosity
enginebouncesraysaroundthesceneand
distributes energy on surfaces. B e tween each
iteration,theenginemeasurestheamountof
variance (noise between surfaces) that was
computed.
Most of the bri ghtness of the scene is d istributed in
the early iterations. The contribution to the scene’s
average brightness decreases logarithmically
between iterations. After the first few iterations,
the brightness of t he scene does not increase much,
but subsequent iterations reduce the variance in
the scene.
Note: The “quality” refers to the accuracy of
energy distribution, not to the visual quality of the
solution. Even at a high Initial Quality percentage,
the scene can still show considerable variance.
This variance is resolved by the subsequent stages
of the solution.
Increasing the percentage value of Initial Q uality.
Increasing quality does not greatly increase the average
brightness of the scene, but it decreases the variance
between different surfaces in the scene, such as the faces
of the sphere.
Ref ine I ter ations (All Objects)—Sets the number
of Refine iterations to perform for the scene as a
whole. The Refine Iterations stage increases the
quality of the radiosity processing on all objects
in the scene. Gathers energy from each face in
order to reduce the variance between faces using
a different process from the Initial Quality stage.
This stage does not increase the brightness of
the scene, but it improves the visual quality of
the solution and significantly reduces variance
between surfaces. If you don’t reach an acceptable
result after processing a certain number of Refine
iterations, you can increase the number and
continue processing.
Tip: If you plan to use Regathering at render time,
you generally don’t need to perform the Refine
stage to get good-quality final renderings.
Note: After 3ds Max processes Refine Iterations,
Initial Quality is disabled and you can’t change it
until you click Reset or Reset A ll.