Solution: z%LIX^q9
The plastic material with the rough diffusing surface can be modeled in P} G+4Sk
TracePro, but as two separate properties (select Define/EditPropertyData). t>B;w14
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MATERIAL PROPERTY 7
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A TracePro Material Property can be created, and the index of refraction of P_p<`sC9
the material is entered here, as well as an absorption coefficient if it is ?8Cq{
known (this would be for absorption losses just from propogating through a *C=>X193U
given thickness of a clear polished sample of the material, unrelated to the ApXy=?fc
diffusing surface finish. Entering zero for the absorption coefficient is a+T.^koY
propobly a reasonable estimate for a transparent material. }XM(:|8J,
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The Material Property is applied to the Object (Define/Apply Properties). qc~iQSI
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SURFACE PROPERTY r_;N t
A TracePro Surface Property can specify 5 possible outcomes for light incident we?76t:-
on a surface - Specular Transmission, Specular Reflection, Scattered =k:,qft2
Transmission (BTDF). Scattered Reflection (BRDF), and Absorption. \A6B,|@
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For your property, I expect that Specular Transmission, Specular Reflection, ^Uh BH@ti
and Absorption would all be 0, leaving only Scattered Transmission (BTDF). k/gZ ,
Scattered Reflection (BRDF). BTDF and BRDF are controlled by 3 coefficients - Bv%GJ*>>
A, B, and g. For an initial estimate, I would suggest entering BTDF(g) = \<6C Z
BRDF(g) = 0, which defines a Lambertian dsitribution. 3nn J8zQ
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The challenge is to determine the proper ratio of Transmittance vs 'W,jMju
Reflectance. You can enter a value for BRDF(A) and then use the Solve For FzXJ]H
feature to solve for BTDF, and the editor will display the resulting A4<Uu~
Integrated BTDF and Integrated BRDF values. You want these to sum to 1, and f_Av3
to have a ratio that matches the behavior of your surface. If the ratio of T n`&U~s8w
vs R is dependent on the Incidence Angle, you can use the Add button in the TSWM
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property to add Incidence ANgles to the table, and then define the BTDF and GU8sO@S5#
BRDF separately for each incidence angle.
