Solution: jJFWPD ] u
The plastic material with the rough diffusing surface can be modeled in L[l ?}\
TracePro, but as two separate properties (select Define/EditPropertyData). T'\B17
:*
$$ %4,\{l
MATERIAL PROPERTY MV
+R $
A TracePro Material Property can be created, and the index of refraction of vvA=:J4/i)
the material is entered here, as well as an absorption coefficient if it is f!6oW( r-L
known (this would be for absorption losses just from propogating through a +Go(y S
given thickness of a clear polished sample of the material, unrelated to the _G s*4:
diffusing surface finish. Entering zero for the absorption coefficient is 3sG7G:4
propobly a reasonable estimate for a transparent material. 5\93-e
@P=St\; VP
The Material Property is applied to the Object (Define/Apply Properties). Yhdt"@;..
' =MaO@ @
SURFACE PROPERTY <@i. ~EL
A TracePro Surface Property can specify 5 possible outcomes for light incident
Y g >W.wA
on a surface - Specular Transmission, Specular Reflection, Scattered z'@j9vT
Transmission (BTDF). Scattered Reflection (BRDF), and Absorption. ^0"^Xk*
n\d`Fk
For your property, I expect that Specular Transmission, Specular Reflection, i9Fg
and Absorption would all be 0, leaving only Scattered Transmission (BTDF). .5Y%I; ~v
Scattered Reflection (BRDF). BTDF and BRDF are controlled by 3 coefficients - $r`K4g
A, B, and g. For an initial estimate, I would suggest entering BTDF(g) = O7 @CAr
BRDF(g) = 0, which defines a Lambertian dsitribution. I9O9V [
` nBCCz'Y!
The challenge is to determine the proper ratio of Transmittance vs 5G .Fi21
b
Reflectance. You can enter a value for BRDF(A) and then use the Solve For %Q]u_0P*
feature to solve for BTDF, and the editor will display the resulting ").MU[ q%Y
Integrated BTDF and Integrated BRDF values. You want these to sum to 1, and *r!f! eA:
to have a ratio that matches the behavior of your surface. If the ratio of T bqug o
vs R is dependent on the Incidence Angle, you can use the Add button in the aE}1~`
property to add Incidence ANgles to the table, and then define the BTDF and .K?',x
BRDF separately for each incidence angle.
