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Arch & Design Material (mental ray) 1555
material’s index of refraction. This is known
as Fresnel reflections and follows the behavior
of most dielectric materials such as water and
glass.
•
Custom R eflectivity Function—When chosen,
the follow ing settings determine reflectivity
based on angle of view.
•
0deg. refl.—Defines the reflectiv ity for
surfaces directly facing the viewer (or
incident ray).
•
90 deg. refl.—Defines the reflectivity of
surfaces perp endicular to the viewer.
•
Curve shape—Defines the fa lloff of the BRDF
cur ve.
This mode is used for most hybrid m aterials
or for metals. Most materials exhibit strong
reflections at g razing angles; hence the 90 degree
reflectivity parameter can generally be kept at
1.0, using the Reflectiv ity parameter to guide the
overall reflectivity instead. Metals tend to be fairly
uniformly reflective and the 0 deg ree reflectivity
value is high (0.8–1.0), but many other layered
materials, such as linoleum and lacquered wood
have lower 0 degree reflectivity va lues, in the range
0.1–0.3). For further information, see Quick Guide
to Some Common Mater ials (page 2–1569).
Ref lectivi ty vs. A ngle gr aph—Depicts the combined
Custom Reflectivity Function settings.
Special Effec ts rollout
Provides settings for ambient occlusion (page
2–1567) (AO) and round corners/edges.
Ambient Occ lu sion grou p
Ambient Occlusion—When on, enables AO and
makes the remaining group controls available.
Samples—The number of samples (rays) shot for
creating AO. Higher values yield smo other results
but render more slowly, while lower values render
faster but look gr ainier. Values in the range 16–64
cover most situations.
Max Distance—Defines the radius within w hich
mental ray looks for occluding objects. Smaller
values restrict the AO effect to smal l crev ices only
but are much faster to render. Larger values cover
larger areas but render more slowly.
The following illustrations show the raw AO
cont ribution with two different distances: