/usr/share/radiance/grating.cal is in radiance-materials 4R1+20120125-1.1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 | {
Specular transmission through a metal grating aligned with x-y plane.
Greg Ward for Visarc 8/25/2004
Use in a BRTDfunc material as follows:
void BRTDfunc grating
10
0 0 0
spectrans spectrans spectrans
0 0 0
grating.cal
0
13
rrefl grefl brefl
rrefl grefl brefl
rtrns gtrns btrns
A10 A11 A12 A13
The additional BRTDfunc parameters are defined as follows:
A10 - Grating bar vertical depth
A11 - Grating bar thickness
A12 - Grating spacing in x-direction (center-to-center)
A13 - Grating spacing in y-direction (center-to-center)
The diffuse reflectance and transmittance can be approximated from
the diffuse reflectance Rd of the underlying material as follows:
refl = Rd*min(1, A11/A12 + A11/A13 + .5*PI*A10/(A12+A13))
trns = Rd*(1-A11/A12-A11/A13)*min(1, .5*PI*A10/(A12+A13))
}
aDx = abs(Dx); aDy = abs(Dy); aDz = abs(Dz);
spectrans = if(1e-6 - aDz, 0,
max(0, (arg(12) - arg(11) - arg(10)*aDx/aDz)/arg(12)) *
max(0, (arg(13) - arg(11) - arg(10)*aDy/aDz)/arg(13)) );
|