Solution: T?4G'84nN
The plastic material with the rough diffusing surface can be modeled in 7Pa@1']
TracePro, but as two separate properties (select Define/EditPropertyData). O]qU[y+
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MATERIAL PROPERTY 28
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A TracePro Material Property can be created, and the index of refraction of *5xJv
the material is entered here, as well as an absorption coefficient if it is p ;|jI1
known (this would be for absorption losses just from propogating through a k__$ Q9qj(
given thickness of a clear polished sample of the material, unrelated to the F{ELSKcp.
diffusing surface finish. Entering zero for the absorption coefficient is *cye O*
propobly a reasonable estimate for a transparent material. NKQOUw:qn
_V\Bp=9W
The Material Property is applied to the Object (Define/Apply Properties). : }`-B 0
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SURFACE PROPERTY Un6/e/6,
A TracePro Surface Property can specify 5 possible outcomes for light incident =|=.>?t6Z0
on a surface - Specular Transmission, Specular Reflection, Scattered n`4K4y%Dy}
Transmission (BTDF). Scattered Reflection (BRDF), and Absorption. j)
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For your property, I expect that Specular Transmission, Specular Reflection, _D|^.)=U|
and Absorption would all be 0, leaving only Scattered Transmission (BTDF). \Y{k7^G}A
Scattered Reflection (BRDF). BTDF and BRDF are controlled by 3 coefficients - >CkjUZu]&
A, B, and g. For an initial estimate, I would suggest entering BTDF(g) = l&}y/t4%
BRDF(g) = 0, which defines a Lambertian dsitribution. R6=$u{D
}W
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The challenge is to determine the proper ratio of Transmittance vs Wq^qpN)5Y
Reflectance. You can enter a value for BRDF(A) and then use the Solve For pC_O:f>vJ
feature to solve for BTDF, and the editor will display the resulting 'TA UE{{
Integrated BTDF and Integrated BRDF values. You want these to sum to 1, and ?-Vjha@BO
to have a ratio that matches the behavior of your surface. If the ratio of T "]-Xmdk09
vs R is dependent on the Incidence Angle, you can use the Add button in the ~@kU3ZGJZ
property to add Incidence ANgles to the table, and then define the BTDF and gkHNRAL
BRDF separately for each incidence angle.
