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{ RCSid $Id: klems_quarter.cal,v 1.5 2015/03/27 18:58:06 greg Exp $ }
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{
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Compute interior bin for quarter Klems BSDF basis (0-40)
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Returns -1 for wrong-side rays
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Modified from klems_full.cal
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7/18/2014 G. Ward
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}
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DEGREE : PI/180;
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Acos(x) : if(x-1, 0, if(-1-x, PI, acos(x))) / DEGREE;
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posangle(a) : if(-a, a + 2*PI, a) / DEGREE;
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Atan2(y,x) : posangle(atan2(y,x));
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kqpola(r) : select(r, 9, 27, 45, 63, 90);
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kqnaz(r) : select(r, 1, 8, 12, 12, 8);
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kqaccum(r) : if(r-.5, kqnaz(r) + kqaccum(r-1), 0);
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kqfindrow(r, pol) : if(r-kqpola(0)+.5, r,
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if(pol-kqpola(r), kqfindrow(r+1, pol), r) );
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kqazn(azi,inc) : if((360-.5*inc)-azi, floor((azi+.5*inc)/inc), 0);
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kqbin2(pol,azi) = if(pol-90, -1,
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select(kqfindrow(1, pol),
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kqazn(azi,360/kqnaz(1)),
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kqaccum(1) + kqazn(azi,360/kqnaz(2)),
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kqaccum(2) + kqazn(azi,360/kqnaz(3)),
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kqaccum(3) + kqazn(azi,360/kqnaz(4)),
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kqaccum(4) + kqazn(azi,360/kqnaz(5))
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) );
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RHS = 1; { set to -1 for left-handed system }
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kqbin(Nx,Ny,Nz,Ux,Uy,Uz) = kqbin2(Acos(-Dx*Nx-Dy*Ny-Dz*Nz),
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Atan2(-Dx*Ux-Dy*Uy-Dz*Uz + (Nx*Dx+Ny*Dy+Nz*Dz)*(Nx*Ux+Ny*Uy+Nz*Uz),
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-RHS*(Dx*(Uy*Nz-Uz*Ny) + Dy*(Uz*Nx-Ux*Nz) + Dz*(Ux*Ny-Uy*Nx))));
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Nkqbins : kqaccum(kqnaz(0)); { Number of bins for one elevation }
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