| lightgirl |
2008-09-16 16:27 |
Solution: Wsp c ;]&
The plastic material with the rough diffusing surface can be modeled in Y
DW^N ] G
TracePro, but as two separate properties (select Define/EditPropertyData). 8GRB6 -.h
L7n G5i
MATERIAL PROPERTY GIT"J}b}
A TracePro Material Property can be created, and the index of refraction of cW_l |
the material is entered here, as well as an absorption coefficient if it is (74y2U 6
known (this would be for absorption losses just from propogating through a GY %$7
given thickness of a clear polished sample of the material, unrelated to the c<lEFk!g
diffusing surface finish. Entering zero for the absorption coefficient is jt(GXgm
propobly a reasonable estimate for a transparent material. ay| |yn:
K<r5jb
The Material Property is applied to the Object (Define/Apply Properties). 2 #00<t\
z,hBtq :-$
SURFACE PROPERTY !G6h~`[
A TracePro Surface Property can specify 5 possible outcomes for light incident s| :1z"q
on a surface - Specular Transmission, Specular Reflection, Scattered x%O6/rl
Transmission (BTDF). Scattered Reflection (BRDF), and Absorption. `8tstWYa]Y
OHW|?hI=[
For your property, I expect that Specular Transmission, Specular Reflection, )Z|G6H`c3
and Absorption would all be 0, leaving only Scattered Transmission (BTDF). SjY|aW+wAL
Scattered Reflection (BRDF). BTDF and BRDF are controlled by 3 coefficients - FC~%G&K/q^
A, B, and g. For an initial estimate, I would suggest entering BTDF(g) = e2K9CE.O
BRDF(g) = 0, which defines a Lambertian dsitribution. L Ee{fc?{
>]%$lSCW\D
The challenge is to determine the proper ratio of Transmittance vs A0RS NA M
Reflectance. You can enter a value for BRDF(A) and then use the Solve For R/Z7}Q W
feature to solve for BTDF, and the editor will display the resulting ADVS}d!;]
Integrated BTDF and Integrated BRDF values. You want these to sum to 1, and eX lJ=S}
to have a ratio that matches the behavior of your surface. If the ratio of T q9PjQ%
vs R is dependent on the Incidence Angle, you can use the Add button in the lzz;L
z
property to add Incidence ANgles to the table, and then define the BTDF and &r*F+gL
BRDF separately for each incidence angle.
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