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88 Chapter 17: Rendering
Shadows with the mental ray
Renderer
The mental ray renderer can generate shadows
by ray tracing. Ray tracing traces the path of
rays sampled from the lig ht source. Shadows
appear where rays have b een blocked by objects.
Ray-traced shadows have sharp edges.
Ray-traced shadows
Turning off caustics makes the outlines of shadows in this
scene easier to see.
You can tell the mental ray renderer to use
shadow maps (page 3–1105) instead of ray-traced
shadows. This can improve performance at a cost
of accuracy.
Shadow controls are on the Render Scene Dialog >
Renderer panel >
Shadows & Displacement rollout
(page 3–111)
.
Shadow Generators and the mental ray
Renderer
Lightobjectsin3dsMaxletyouchooseashadow
generator: Ray Traced, Advanced Ray Traced,
Shadow Map, and so on. B ecause the mental
rayrenderersupportsonlytwokindsofshadow
generation, ray tracing and shadow maps, some
of the 3ds Max shadow generators aren’t fully
supported.
In 3ds Max, a special shadow generator type,
mental ray Shadow Map, is provided to support
the mental ray renderer. If shadows are enabled
(on the
Shadows & Displacement rollout (pa ge
3–111)
of the Render Scene dialog) but shadow
maps are not enabled, then shadows for all lights
are generated using the ment a l ray ray-tracing
algorithm. If shadow maps are enabled, then
shadow generation is based on each light’s choice
of shadow generator:
•
mental ray Shadow M ap—Shadows are
generated using the mental ray shadow-map
algorithm.
•
Shadow Map—Settings on the Shadow
Parameters rollout are translated into a mental
ray equivalent before shadows are generated.
The qualit y of shadows generated this way
might not always meet expectations.
•
Area Shadows, Advanced R ay Traced S hadows, or
Ray Traced Shadows—
Shadows are generated
using the mental ray r ay-tracing algorithm.
Motion B lur with the mental ray
R enderer
Motion blur is a way to enhance the realism of
a rendered animation by simulating the way a
real-world camera works. A camera has a shutter
speed, and if significant movement occurs during
thetimetheshutterisopen,theimageonfilmis
blurred.