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116 Chapter 17: Rendering
Edge Length—
Defines the smal lest potential edge
length due to subdivision. The mental ray renderer
stops subdividing an edge once it reaches this size.
Default=2.0 pixels.
Max. Displace—Controls the maximum offset, in
world units, that can be given to a vertex when
displacing it. T his value can affect the bounding
box of an object. Default=20.0.
Tip: If displaced geometr y appears to be “clipped,”
try increasing the va lue of Maximum Displace.
Note: When using placeholders (see the Translator
Options rollout (page 3–119)), if this value is larger
than it needs to be, it can reduce performance. If
youexperienceslowtimeswhiledisplacedobjects
when Use Placeholder Objects is on, try lowering
theMax.Displacevalue.
Max. Subdiv.—Controls the extent to which mental
ray can recursively subdivide each original mesh
triangle for displacement. Each subdivision
recursion potentially divides a single face into
four smal ler faces. Choose the value from the
drop-down list. Range=4 to 64K (65,536).
Default=16K (16,384).
For example, using the default value means that
mental ray can subdivide each d isplaced mesh
triangle into as many as 16,384 smaller triang les.
Render ing Algor ithms R ollout
(menta l r ay R end er er )
Rendering menu > Render > Render Scene dial og >
Renderer panel > Rendering Algorithms rollout
Main toolbar > Render Scene > Render Scene dialog >
Renderer panel > Rendering Algorithms rollout
Note: The Renderer panel appears o nly when the mental
ray renderer is the cur rently active renderer.
Thecontrolsinthisrolloutletyouchoosewhether
to render using ray-tracing, scanline rendering,
or both. You can also choose the method used to
accelerate ray-tracing.
The controls labeled Trace Depth limit the number
of times each ray can be reflected, refracted, or
both.
Procedure
To set tra ce d epth for r efl ections a nd r efr actions:
1.
Coun t the number of times you want an object
to be reflected or refracted in the scene.
2. On the mental ray: Rendering Algorithms
rollout, set Max Reflections to the number of
reflections you want, and Max Refractions to
the number of refractions you want.
3. Set Max Depth to equal the value you chose for
Max Reflections plus the value you chose for
Max Refractions.
Thegreaterthenumberofreflectionsand
refractions, the more slowly your scene will
render. On the other hand, too low a value
for Max Reflections or Max Refrac tions (or
Max Depth, controlling both) can make your
rendering look unrealistic.