| lightgirl |
2008-09-16 16:27 |
Solution: QSOG( }w
The plastic material with the rough diffusing surface can be modeled in P+DIo7VTX
TracePro, but as two separate properties (select Define/EditPropertyData). 6 !wk5#
-!
^D8^ s
MATERIAL PROPERTY kq@~QI?9
A TracePro Material Property can be created, and the index of refraction of R$;TX^r'o&
the material is entered here, as well as an absorption coefficient if it is * NC@o*
known (this would be for absorption losses just from propogating through a TQ =HFs
~
given thickness of a clear polished sample of the material, unrelated to the \} _, g
diffusing surface finish. Entering zero for the absorption coefficient is w@LLxL>Y
propobly a reasonable estimate for a transparent material. ygQe'S{!S\
L2OR<3*|Av
The Material Property is applied to the Object (Define/Apply Properties). e0hY
6w[EJ;=p_
SURFACE PROPERTY my#\(E+
A TracePro Surface Property can specify 5 possible outcomes for light incident G=| ~SYz
on a surface - Specular Transmission, Specular Reflection, Scattered fg4mP_
Transmission (BTDF). Scattered Reflection (BRDF), and Absorption. d0;?GQYn:
^!gq_x
For your property, I expect that Specular Transmission, Specular Reflection, <>)N$$Rx&
and Absorption would all be 0, leaving only Scattered Transmission (BTDF). `\f 3Ij,
Scattered Reflection (BRDF). BTDF and BRDF are controlled by 3 coefficients - ?hViOh$.
A, B, and g. For an initial estimate, I would suggest entering BTDF(g) = |#'n VN.;
BRDF(g) = 0, which defines a Lambertian dsitribution. mv^X{T
tHK>w%|\R
The challenge is to determine the proper ratio of Transmittance vs JfmYr47Pv
Reflectance. You can enter a value for BRDF(A) and then use the Solve For cQm4q19
feature to solve for BTDF, and the editor will display the resulting 73Hm:"Eqd
Integrated BTDF and Integrated BRDF values. You want these to sum to 1, and w^U{e
xo
to have a ratio that matches the behavior of your surface. If the ratio of T ;; ;=)'o
vs R is dependent on the Incidence Angle, you can use the Add button in the lc3Gu78 A/
property to add Incidence ANgles to the table, and then define the BTDF and (>NZYPw^3
BRDF separately for each incidence angle.
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