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{ RCSid $Id: klems_full.cal,v 1.3 2015/03/27 18:58:06 greg Exp $ }
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{
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Compute interior bin for (full) Klems BSDF basis (0-144)
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Returns -1 for wrong-side rays
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Modified from Tregenza.cal, which is similar but different
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6/14/2009 G. Ward
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}
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DEGREE` : PI/180;
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mod`(n,d) : n - floor(n/d)*d;
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Acos(x) : if(x-1, 0, if(-1-x, PI, acos(x))) / DEGREE;
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kpola(r) : select(r, 5, 15, 25, 35, 45, 55, 65, 75, 90);
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KAPS : kpola(3) - kpola(2);
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knaz(r) : select(r, 1, 8, 16, 20, 24, 24, 24, 16, 12);
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kaccum(r) : if(r-.5, knaz(r) + kaccum(r-1), 0);
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kfindrow(r, pol) : if(r-kpola(0)+.5, r,
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if(pol-kpola(r), kfindrow(r+1, pol), r) );
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RHS = 1; { Set to -1 for left-handed system }
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JTR = 0; { Sharp bin boundaries by default }
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{ Uniform perturbation function }
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kjtr(n) = if(JTR, JTR*(.5 - rand(n*(9.54*Dx - 5.11*Dy + 1.37*Dz - 6.71))), 0);
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kazn(azi,inc) = floor( mod(azi + inc*(.5+kjtr(2)), 360) / inc );
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kbin2(pol,azi) =
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select(kfindrow(1, pol),
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kazn(azi,360/knaz(1)),
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kaccum(1) + kazn(azi,360/knaz(2)),
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kaccum(2) + kazn(azi,360/knaz(3)),
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kaccum(3) + kazn(azi,360/knaz(4)),
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kaccum(4) + kazn(azi,360/knaz(5)),
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kaccum(5) + kazn(azi,360/knaz(6)),
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kaccum(6) + kazn(azi,360/knaz(7)),
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kaccum(7) + kazn(azi,360/knaz(8)),
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kaccum(8) + kazn(azi,360/knaz(9))
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);
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kbin1(zv,yv,xv) = if(zv, kbin2(min(max(0, Acos(zv) + KAPS*kjtr(1)), 90),
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atan2(yv,xv)/DEGREE),
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-1);
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kbin(Nx,Ny,Nz,Ux,Uy,Uz) = kbin1(-Dx*Nx-Dy*Ny-Dz*Nz,
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-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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kbinN = kbin(0,-1,0, 0,0,1); { North bins }
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kbinE = kbin(-1,0,0, 0,0,1); { East bins }
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kbinS = kbin(0,1,0, 0,0,1); { South bins }
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kbinW = kbin(1,0,0, 0,0,1); { West bins }
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kbinD = kbin(0,0,-1, 0,1,0); { Skylight bins }
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Nkbins : kaccum(knaz(0)); { Number of bins for one elevation }
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