[Radiance-general] Unsure how to specify a trans modifier

[P George Lovell]

Hi Everyone,

I'm trying to create a material with properties of a leaf - for a 
project examining countershading camouflage in animals, I've created 
model trees and I want them to be green in colour but with leaf-like 
transmission of light to the forest floor.

For example, I might want the colour to be [.3 .7 .1] and the 
transmission to be [.05 .25 .02].

Here's a mock-up of what I'm working on: 
https://www.dropbox.com/s/cidluvy1h8u7jqd/Horse_Trees_Panels.png.


To make it really obvious that light is passing through the material 
I've added the two floating panels, the left is opaque and the right one 
allows red light to pass through (at least it should, but I'm not 
getting any difference in the colour of the shadows).

Do I specify a colour plastic material and then a trans modifier and 
then the polygon? I've tried various script formats, so far when it 
doesn't crash I get no noticeable difference in the images with and 
without transmission specified as above.

Here's a script that just specifies a grey ground and the two green panels:


=======================================================


void plastic backgroundPolygon
0
0
5    0.2000    0.2000    0.2000    0.0000    0.2000

backgroundPolygon polygon rectangle_1v
0
0
12
     5000000.0000    -5000000.0000    000.0000
     5000000.0000    5000000.0000    000.0000
     -5000000.0000    5000000.0000    -00.0000
     -5000000.0000    -5000000.0000    -00.0000

void plastic backgroundPolygon
0
0
5    0.2000    0.7000    0.1000    0.0000    0.2000

backgroundPolygon polygon rectangle_1v
0
0
12
     500.0000    1000.0000    500.0000
     500.0000    2000.0000    500.0000
     -500.0000    2000.0000    500.0000
     -500.0000    1000.0000    500.0000

void trans rectangle_1i_trans
0
0
3
1.00 0.00 0.00

rectangle_1i_trans plastic backgroundPolygon
0
0
5    0.2000    0.7000    0.1000    0.0000    0.2000

backgroundPolygon polygon rectangle_1i
0
0
12
     500.0000    -2000.0000    500.0000
     500.0000    -1000.0000    500.0000
     -500.0000    -1000.0000    500.0000
     -500.0000    -2000.0000    500.0000

=======================================================

I'm clearly doing something wrong, but I've no idea exactly what.

Best wishes once again,

George





-- 
Dr P. George Lovell,

Lecturer in Psychology
University of Abertay Dundee
Dundee
DD1 1HG

Tel 01382-308581
Fax 01382-308749

Researcher/Co-investigator,
School of Psychology, University of St Andrews

RM 2.27 (The Yellow Room).
Phone      (01334) 463056