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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