| lightgirl |
2008-09-16 16:27 |
Solution: C# r_qn
The plastic material with the rough diffusing surface can be modeled in TJY$<:
TracePro, but as two separate properties (select Define/EditPropertyData). ?Di, '
, IUMH]D
MATERIAL PROPERTY 3w )S=4lB
A TracePro Material Property can be created, and the index of refraction of *9^CgLF
the material is entered here, as well as an absorption coefficient if it is SX}GKu
known (this would be for absorption losses just from propogating through a |xz qYu?o
given thickness of a clear polished sample of the material, unrelated to the v >3ctP {
diffusing surface finish. Entering zero for the absorption coefficient is 9\)NFZ3Mz
propobly a reasonable estimate for a transparent material. ,Ucb)8a
wrG*1+r
The Material Property is applied to the Object (Define/Apply Properties). `n-e.{O((
i/x PO
SURFACE PROPERTY X_
>B7(k
A TracePro Surface Property can specify 5 possible outcomes for light incident z>j%-3_1
on a surface - Specular Transmission, Specular Reflection, Scattered 5*buRYck0
Transmission (BTDF). Scattered Reflection (BRDF), and Absorption. Ao96[2U6
wri[#D {
For your property, I expect that Specular Transmission, Specular Reflection, :&)RK~1m_
and Absorption would all be 0, leaving only Scattered Transmission (BTDF). ;_j\E(^%
Scattered Reflection (BRDF). BTDF and BRDF are controlled by 3 coefficients - ;$i9gP[|m
A, B, and g. For an initial estimate, I would suggest entering BTDF(g) = mC~W/KReA
BRDF(g) = 0, which defines a Lambertian dsitribution. 9+QLc b
Cu;X{F'H
The challenge is to determine the proper ratio of Transmittance vs Op3 IL/
Reflectance. You can enter a value for BRDF(A) and then use the Solve For z,rWj][P
feature to solve for BTDF, and the editor will display the resulting aic6,>\!'
Integrated BTDF and Integrated BRDF values. You want these to sum to 1, and B_c n[?M
to have a ratio that matches the behavior of your surface. If the ratio of T ^e>v{AE%
vs R is dependent on the Incidence Angle, you can use the Add button in the W r)% C
property to add Incidence ANgles to the table, and then define the BTDF and lRt8{GFy
BRDF separately for each incidence angle.
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