8
112 Chapter 17: Rendering
• Shadow Ma p—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 Sha dows, Adva nced R ay Tra ced Sha dows, or
Ray Traced Shadows—
Shadows are generated
using the mental ray r ay-tracing algorithm.
Motion B lur—When on, the mental ray renderer
applies
motion blur (page 3–88)
to shadow maps.
Default=on.
Wa rn in g: 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 R e-Use Cache)—
When on, the
renderer saves the recalculated
shadow map (.zt)
file (page 3–1131)
tothefilespecifiedbythe
Browse button. Default=on.
•
Use File—When on, the mental ray renderer
either saves the shadow map to a .
zt
file, or loads
an existing file. The state of Rebuild determines
whether the .
zt
file is saved or loaded.
This option is unavailable unless you click
Browse (“...”) 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—When you have used the Save
button to specify a shadow map file, this field
displays its name and path.
•
Delete File—Click to delete the current .
zt
file.
Displacement group
View—Defines the space for d isplacement. 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—Tur n off to h ave the ment al r ay
renderer correctly render height maps. Height
maps c an be gener ated by norm al mapping; see
Creating and Using Normal Bump Maps (page
3–146)
.
When using only height maps in the scene, make
sure this option 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 (O bject Properties
Dialog) (page 1–121)
).
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.
Edge Length—Defines the smallest edge length.
The mental ray renderer will stop subdividing an
edge once it reaches this size. Default=2.0 pixels.
Max. Displace—Controls the maximum offset, i n
world units, that can be given to a vertex when
displacing it. This value can affect the bounding
box of an object. Default=20.0.
Tip: If displaced geometry appears to be “clipped,”
try increasing the value of Maximum Displace.
Note: When using placeholders (see the
Translator
Options rollout (page 3–115)
), if this value is larger
than it needs to be, it can reduce performance. If
you experience slow times while displaced objects
when Use Placeholder Objects is on, try lowering
the Max. Displace value.
Max. Level—Controls how many t imes a t riangle
can be subdivided. Default=6.