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Arch & Design Material (mental ray) 1551
Glossy S amples—
Defines the maximum number
of samples (rays) that mental ray shoots to crea te
glossy reflections. Higher values cause slow
rendering but create a smoother result. L ower
values render faster but create a gr ainier result.
Generally 32 is enough for most cases.
Av ai lable only when Glossiness does not equal 1.0.
Because a Glossiness value of 1.0 creates a “perfect
mirror,” it is meaningless to shoot multiple rays for
this case, hence only one reflection ray is shot.
Note: If you set Glossy Samples to 0, the reflections
take the form of a “perfect mirror” and only
onerayisshot,regardlessoftheactualvalueof
Glossiness . You can use this to boost performance
for surfaces with very weak reflections. The
highlight still respects the Glossiness value.
Glossy reflections need to trace multiple r ays
to yield a smooth result, which can affect
perf ormance. For this reason, the ma terial
includes the following two special features
designed to enhance performance:
Fast (interpolate)—When on, a smoothing
algorithmallowsraystobereusedandsmoothed.
The result is f aster and smoother glossy reflections
at the expense of accuracy. Interpolation is
explained in greater detail in the section on the
Fa st Glossy Interpolation rollout (page 2–1559).
Note: This method works best on flat surfaces.
Highlights+FG only—When on, mental ray traces
no actual reflection rays. Instead, only the
highlights are shown , as well as soft reflections
emulated with the help of using Final Gathering.
The Highlights+FG Only mode takes no
additional rendering time compared to a
non-glossy (diffuse) surface, yet can yield
surprisingly conv incing results. While it might not
be completely convincing for “hero” objects in a
scene, it can work very well for less-essential scene
elements. It tends to work best on materials with
weak reflect ions or extremely glossy (blurred)
reflections,asshowninthefollowingillustration:
Thetwocupsontheleftuserealreflections,whilethoseonthe
right use Highlights+FG Only.
Metal material—Metallic objects actually influence
the color of their reflection, whereas other
materials do not. For example, a gold bar w i ll have
gold colored reflections, but a red glass orb does
not have red reflections. This is supported through
the Metal Material option:
• When off, the Reflection Color parameter
defines the color, and the Reflectivity parameter
together with the BRDF settings defines the
intensity and colors of reflections.
• When on, the Diffuse Color parameter defines
the color of reflections, and Reflectivity
parameter sets the “weight” between diffuse
reflect ions and glossy (metal lic) reflections.
Left: Non-metallic reflections (Metal Material is off). Reflections
clearly contain the color of the objects they reflect and are not
influenced by the color of the materials.
Center: Metallic reflections (Metal Material is on). Now the
color of reflections are influenced by the color of the object.
Right: A variant of this with Reflectivity=0.5, creating a 50:50
mix between colored reflections and diffuse reflections