Solution: W;Y^ (f
The plastic material with the rough diffusing surface can be modeled in J,
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TracePro, but as two separate properties (select Define/EditPropertyData). Hw o _;fV
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MATERIAL PROPERTY -Cs( 3[
A TracePro Material Property can be created, and the index of refraction of ,* J@ic7"
the material is entered here, as well as an absorption coefficient if it is F:!6B b C
known (this would be for absorption losses just from propogating through a Z*m^K %qJ
given thickness of a clear polished sample of the material, unrelated to the hOwb
diffusing surface finish. Entering zero for the absorption coefficient is 509T ? \r
propobly a reasonable estimate for a transparent material. gx.\H3y
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The Material Property is applied to the Object (Define/Apply Properties). ?4bYb]8Z
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SURFACE PROPERTY cXPpxRXBD
A TracePro Surface Property can specify 5 possible outcomes for light incident , c&u\W=p
on a surface - Specular Transmission, Specular Reflection, Scattered ,`}y J*7
Transmission (BTDF). Scattered Reflection (BRDF), and Absorption. a9-Mc5^'n
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For your property, I expect that Specular Transmission, Specular Reflection, ^%$ Id Dx
and Absorption would all be 0, leaving only Scattered Transmission (BTDF). k|/VNV( =0
Scattered Reflection (BRDF). BTDF and BRDF are controlled by 3 coefficients - Rn~'S2`u
A, B, and g. For an initial estimate, I would suggest entering BTDF(g) = mD'nF1o
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BRDF(g) = 0, which defines a Lambertian dsitribution. ,)1C"'
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The challenge is to determine the proper ratio of Transmittance vs KnkmGy
Reflectance. You can enter a value for BRDF(A) and then use the Solve For .dU91> ~Ov
feature to solve for BTDF, and the editor will display the resulting ~JT`q: l-q
Integrated BTDF and Integrated BRDF values. You want these to sum to 1, and gw)4P tb!
to have a ratio that matches the behavior of your surface. If the ratio of T Cw,a )XB
vs R is dependent on the Incidence Angle, you can use the Add button in the 4
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property to add Incidence ANgles to the table, and then define the BTDF and ^3dc#5]Xf
BRDF separately for each incidence angle.
