Solution: g
,`F<CF9
The plastic material with the rough diffusing surface can be modeled in u2 Y N[|V
TracePro, but as two separate properties (select Define/EditPropertyData). v: giZxR
JaA&e T|
MATERIAL PROPERTY ]F
!'M
A TracePro Material Property can be created, and the index of refraction of 9U&~(;
the material is entered here, as well as an absorption coefficient if it is E1#H{ )G
known (this would be for absorption losses just from propogating through a l +|1G
given thickness of a clear polished sample of the material, unrelated to the (Z5q&#f
diffusing surface finish. Entering zero for the absorption coefficient is mlD%d!.
propobly a reasonable estimate for a transparent material. GI}4,!^N
+I*k0"gj6
The Material Property is applied to the Object (Define/Apply Properties). G aha Z
F
p@vpd
SURFACE PROPERTY AbL5 !'
A TracePro Surface Property can specify 5 possible outcomes for light incident @ <|6{N<
on a surface - Specular Transmission, Specular Reflection, Scattered :wF b5 "
Transmission (BTDF). Scattered Reflection (BRDF), and Absorption. >ze>Xr'm5=
j[_t6Z
For your property, I expect that Specular Transmission, Specular Reflection, dUI3erO
and Absorption would all be 0, leaving only Scattered Transmission (BTDF). Um/CR!
Scattered Reflection (BRDF). BTDF and BRDF are controlled by 3 coefficients - >9 q]> fJ
A, B, and g. For an initial estimate, I would suggest entering BTDF(g) = bh{E& 1sLh
BRDF(g) = 0, which defines a Lambertian dsitribution. f+{c1fb>s
0Wjd-rzc,
The challenge is to determine the proper ratio of Transmittance vs #c6ui0E%;t
Reflectance. You can enter a value for BRDF(A) and then use the Solve For X";TZk
feature to solve for BTDF, and the editor will display the resulting 7F,07\c
Integrated BTDF and Integrated BRDF values. You want these to sum to 1, and iz Xbp02
to have a ratio that matches the behavior of your surface. If the ratio of T th5
X? so
vs R is dependent on the Incidence Angle, you can use the Add button in the dz{#"No0
property to add Incidence ANgles to the table, and then define the BTDF and Dq{: R
BRDF separately for each incidence angle.
