2008

■ The mental ray renderer disregards the bias parameters in the Shadow Map
Params rollout and the Ray Traced Shadow Params rollout.
■ The mental ray renderer assumes that all directional lights come from
infinity, so objects that are behind the direct light object in the 3ds Max
scene will also be illuminated.
Ray Tracing
The mental ray ray tracer is fast and provides excellent quality images, but
you have to use it correctly within 3ds Max.
The mental ray renderer does not fully support cubic maps for
Reflect/Refract
maps
on page 5791 . It uses them if they have already been generated by the
default scanline renderer, but it does not generate them. If Source > From File
is active and the mental ray renderer can find the six cubic maps, it uses them.
If Source > Automatic is active, or if the cubic maps cannot be found, the
mental ray renderer generates ray-traced reflections or refractions instead.
Ray Tracing Setup
On the rendering menu, Ray Tracer Settings and Raytrace Global
Include/Exclude are disabled while the mental ray renderer is active. These
controls adjust ray-trace settings for the scanline renderer only. The settings
of these controls have no impact on the mental ray renderer. The ray-tracing
controls for mental ray appear on the Renderer panel >
Rendering Algorithms
rollout
on page 6118 .
TIP While the mental ray renderer ignores the global inclusion or exclusion settings
for the ray tracer, you can enable or disable ray-tracing at the local level of a
Raytrace material or map.
Ray Tracing Rules of Thumb
Let’s say you’re rendering a (lathed) wineglass, with an inner and outer surface
and a piece of geometry representing the wine. The wine geometry is just
slightly smaller than the inner surfaces of the wineglass, and capped with a
flat top. Now, you go to render the glass. After rendering the scene, however,
there’s something wrong: the inner surfaces of the glass don’t seem reflective
enough, and the wine isn’t refracting properly. What’s wrong?
What’s wrong is that you probably have the number of reflections and
refractions set too low for the number of surfaces you have. To check this, go
to the Renderer panel >
Rendering Algorithms rollout on page 6118 and look
mental ray Renderer | 6045