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Glass Material (mental ray) 1391
Glass Mater ial (mental ray)
Material Editor > Type button > Material/Map Browser >
Glass (physics_phen)
Note: The Glass material does not appear in the Browser
unless you have enabled the mental ray extensions by
using the m ental ray Preferences panel. In addition, you
can’t assign shaders to the options in this rollout unless
the mental ray renderer is the currently active renderer.
The Glass mater ia l simulates both the surface
properties and the light-transmitting (photon)
properties of glass. It is a mental r ay phenomenon
(a scripted shader tree) that is e quivalent to
a
mental ray material (page 2–1385) with a
Dielectric Material shader (page 2–1529) assigned
to both its Surface and Photon components,
w ith the parameter settings identical for both.
A dielectr ic material, such as g lass, is a material
whose sur face transmits most light that strikes it
at angles close to perpendicular (90 degrees), but
reflects most light that strikes at glancing angles
(close to zero degrees).
Note: This material does not use a shadow shader,
soshadowswillalwaysbeopaqueunlessyou
generate caustics.
Adjacent R efractive Materials
Two controls, Outside Light Persistence and Index
Of Refrac tion (O ut), are for situations where you
are modeling two adjacent refractive materials.
Consider a drink in a martini glass. The glass
has an index of refraction (IOR) of 1.5, while the
alcohol in the glass has an IOR of about 1.3. To
create a physically accurate mo del of t his situation,
use
three glass materials: one for the glass itself,
one for the alcohol, and a third material for the
surfaces where they touch each other. For this
third material, set the “inside” IOR to 1.3, and the
outside IOR to 1.5.
Interfa ce
Light Persistence—In conjunction with the
Persistence Distance, controls the percentage of
lightthatthevolumetransmits. Forexample,if
the color is set to R=G=B=0.5 and the Persistence
Distance is set to 2.0, then objects with a thickness
of 2.0 units wi l l appear 50 per cent transparent.
Default=white (R=G=B=1.0).
Be cause transparency depends on the thickness of
the object, objects with var ying thickness show
different transparency depending on the angle
from which they are viewed.
Index Of Refraction—Specifies the Index Of
Refrac tion (IOR). In the physical world, the IOR
results from the relative speeds of light through
thetransparentmaterialandthemediumtheeye
orthecameraisin.Typicallythisisrelatedtothe
object’s density. The higher the IOR, the denser
the object. Default=1.5.
See
Extended Parameters Rollout (Standard
Material) (page 2–1312)
for a list of IOR values for
commonly encountered materials.
Outside Light Persistence—In conjunction with the
Persistence Distance, controls the percentage of
light transmitted on the other side of a surface.
When set to the default of black, this control has
no effect. See the section “Adjacent Ref r ac t ive
Materials,” above. D efault=black (R=G=B=0.0).