9

Shadows and Displacement Rollo ut (mental ray Renderer) 115
shadow map file, the mental ray renderer uses the
shadow map instead of ray-traced shadows.
To stop using a shadow map and use ray-traced
shadows, delete the map’s name from the file name
field.
Enable—When on, the mental r ay renderer renders
shadow-mapped shadows. When off, all shadows
are ray-traced. Default=on.
When Enabled is off, the other controls in this
group are unavailable.
If shadows are enabled but shadow maps are not
enabled, then shadows for all lights are generated
using the mental 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 Map—Shadows are
generated using the mental ray shadow-map
algor ithm.
•
Shadow Map—Settings on the Shadow
Parameters rollout are translated into a mental
ray equivalent before shadows are generated.
The quality of shadows generated this way
might not always meet expectations.
•
Ar ea S ha dows, A dva nced R a y Traced Sha dows, or
Ray Traced Shadows—
Shadows are generated
using the mental ray ray-tracing algorithm.
Motion B lur—When on, the mental ray renderer
applies motion blur (page 3–89) to shadow maps.
Default=on.
Wa rning: Turning on Motion Blur for both cameras an d
shadows can cause shadows to shift position. To avoid
this effect, turn on motion blur for cameras only.
Rebuild (Do Not Re-Use Cache)—
When on, the
renderer saves the recalculated shadow map (.zt)
file (page 3–1037) tothefilespecifiedbythe
Browse button. Default=on.
•
Use File—When on, the mental ray renderer
either saves the shadow map to a ZT file, or
loadsanexistingfile. ThestateofRebuild
determines whether the ZT file is saved or
loaded.
This option is unavailable until you click the
ellipsis button (see following) to provide a
name for the ZT file.
•
... [browse]—Click to display a file selector
dialog, which lets you specify a name for the
shadow map ZT file and the folder where it is
saved.
•
File name—After you specify a shadow map file
(see preceding), this field displays its name and
path.
•
Delete File—Click to delete the current ZT
file.
Displacement group
View—Defines the space for displacement. When
View is on, the Edge Length specifies the length in
pixels. When off, the Edge Length is specified in
world space units. Default=on.
Smoothing—Turn off to have the mental ray
renderer correctly render height maps. Height
maps can be generated by normal mapping; see
Creating and Using Normal Bump Maps (page
3–150).
When using only heig ht maps in the scene, m ake
sure this opt ion is off. If some objects in the
scene use height maps while others use standard
displacement, apply smoothing on a per-object
basis (see mental ray Panel (Object Properties
Dialog) (page 1–126)).
When on, mental ray simply smoothes the
geometry using the interpolated normals, making
the geometry look better. This result, however,
cannot be used for height map displacement
because smoothing affects geometr y in a way that
is incompatible with height mapping.