/usr/share/radiance/lcp0.cal is in radiance-materials 4R0+20110410-1build1.
This file is owned by root:root, with mode 0o644.
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The laser cut panel (LCP) with cuts normal to the surface
A1 = D/W ratio (cut spacing divided by cut depth)
A2 = n, refractive index of panel material (1.5 for acrylic)
The panel is oriented in the yz plane with normal to the
front face in the x direction. Cuts are parallel to the y direction.
Deflection is restricted to the z direction.
The effects of multiple internal reflections and
reflection losses are considered.
The two strongest components (of undeflected, deflected and reflected
components) are displayed.
Example material definition (LCP turned with outward normal in y direction,
D/W=0.5, n=1.5):
void prism2 lcpmat
11 f1 dx1 dy1 dz1 f2 dx2 dy2 dz2 lcp0.cal -rz 90
0
2 0.5 1.5
The same material, transmitted components only:
void prism2 lcpmat_t
11 fu Dx Dy Dz fd Dx Dy -Dz lcp0.cal -rz 90
0
2 0.5 1.5
Phillip Greenup 3/9/98
}
{ Fresnel calculations of transmission and reflection }
cos_i=abs(Rdot);
cos_t=sqrt(A2*A2-1+cos_i*cos_i);
rte=(cos_i-cos_t)/(cos_i+cos_t);
rtm=(A2*A2*cos_i-cos_t)/(A2*A2*cos_i+cos_t);
R=(rte*rte+rtm*rtm)/2;
T=1-R;
{ Fractions deflected and undeflected }
tan_rp=abs(Dz)/(sqrt(A2*A2-1+Dx*Dx));
m=floor(tan_rp/A1);
fd0=(tan_rp/A1)*(-1)^m+2*floor((m+1)/2)*(-1)^(m+1);
fu0=1-fd0;
fd=fd0*T*T;
fu=fu0*T*T;
{ Selection of two strongest components }
N1=if(fu-fd,if(fu-R,1,3),if(fd-R,2,3));
N2=if(fu-fd,if(fu-R,if(fd-R,2,3),1),if(fd-R,if(fu-R,1,3),2));
f1=select(N1,fu,fd,R);
dx1=select(N1,Dx,Dx,-Dx);
dy1=Dy;
dz1=select(N1,Dz,-Dz,Dz);
f2=select(N2,fu,fd,R);
dx2=select(N2,Dx,Dx,-Dx);
dy2=Dy;
dz2=select(N2,Dz,-Dz,Dz);
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