Solution: + .[ <%
The plastic material with the rough diffusing surface can be modeled in ^A/k)x6
TracePro, but as two separate properties (select Define/EditPropertyData). n0 {i&[I~+
3z?> j]
MATERIAL PROPERTY
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A TracePro Material Property can be created, and the index of refraction of I; |B.j
the material is entered here, as well as an absorption coefficient if it is }@+0/W?\.
known (this would be for absorption losses just from propogating through a :U%W%
given thickness of a clear polished sample of the material, unrelated to the x~~|.C ,
diffusing surface finish. Entering zero for the absorption coefficient is }!r|1$,kL
propobly a reasonable estimate for a transparent material. ^"2J]&x`G
E6ElNgL
The Material Property is applied to the Object (Define/Apply Properties). Qd$nH8ED Y
mxC;?s;~
SURFACE PROPERTY WX?IYQ +
A TracePro Surface Property can specify 5 possible outcomes for light incident f }f9@>.
on a surface - Specular Transmission, Specular Reflection, Scattered #OD/$f_
Transmission (BTDF). Scattered Reflection (BRDF), and Absorption.
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7,o7Cf2 z
For your property, I expect that Specular Transmission, Specular Reflection, i%]EEVmN
and Absorption would all be 0, leaving only Scattered Transmission (BTDF). 6SkaH<-&K
Scattered Reflection (BRDF). BTDF and BRDF are controlled by 3 coefficients -
xF'EiX ~
A, B, and g. For an initial estimate, I would suggest entering BTDF(g) = 06Sc eq
BRDF(g) = 0, which defines a Lambertian dsitribution. ?M9=yA
0@iY :aF
The challenge is to determine the proper ratio of Transmittance vs [D4SW#
Reflectance. You can enter a value for BRDF(A) and then use the Solve For <uw9DU7G
feature to solve for BTDF, and the editor will display the resulting x*U)Y
Integrated BTDF and Integrated BRDF values. You want these to sum to 1, and *fS"ym@
to have a ratio that matches the behavior of your surface. If the ratio of T K`zdc`/
vs R is dependent on the Incidence Angle, you can use the Add button in the 9IfmW^0
property to add Incidence ANgles to the table, and then define the BTDF and N
+_t-5
BRDF separately for each incidence angle.
