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1364 Chapter 15: Lights and Cameras
shadow-generation technique for a light. You
select this in the General Par ameters rollout (page
2–1331).
Inter face
Bias—Map Bias (page 3–966) moves the shadow
toward or away from the shadow-casting object
(or objects).
Left: Default shadows
Right: Increasing the Bias value separates the shadow from
the object.
If the Bias value is too low, shadows can "leak"
through places they shouldn’t, produce moire
patterns or making out-of-place dark areas on
meshes.IfBiasistoohigh,shadowscan"detach"
from an object. If t he Bias value is too extreme in
either direction, shadows might not be rendered
at all.
This value depends on whether Absolute Map Bias
is on or off:
• When Absolute is off (the default), Bias is
calculated based on t he scene extents, and
then normalized to one. This provides similar
default shadow results, regardless of scene size.
User adjustments to Bias are typically low
decimal values near 1.0 (for example, 1.2).
• WhenAbsoluteison,Biasisavaluein3dsMax
units. Us er adjustments to Bias depend on the
size of the scene, and can range from values
closetozerotovaluesinthehundreds(seethe
Tip at the end of this topic).
Left: Too small a Bias value causes shadow “leaks.”
Right: Increasing the Bias value fixes the problem.
Size—Sets the size (in pixels squared) of the
shadow map that’s computed for the light.
The shadow map size specifies the amount of subdivisions for
the map. The greater the value, the more detailed the map
will be.
Left: Size set to 32.
Right: Size set to 256.