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{ RCSid $Id: reinhartb.cal,v 2.6 2015/03/27 18:58:06 greg Exp $ }
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{
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Compute Reinhart high-density sky patch bin (rbin)
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RHS - right-handed system?
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JTR - bin jitter/mixing amount
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MF - Subdivision value (usually a power of two)
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Dx,Dy,Dz - Incident direction (normalized, towards surface face)
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rNx,rNy,rNz - Surface normal (normalized, away from surface)
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Ux,Uy,Uz - Up direction vector (does not need to be normalized)
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Modified from reinhart.cal
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July 2014 G. Ward
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}
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{ Useful factors and functions }
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DEGREE` : PI/180;
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mod`(n,d) : n - floor(n/d)*d;
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Asin(x) : if(x-1, PI/2, if(-1-x, -PI/2, asin(x))) / DEGREE;
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Atan2(y,x) : mod( atan2(y,x)/DEGREE, 360);
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{ Default to Tregenza sky }
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MF = 1;
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{ Set to -1 for left-handed coordinate system }
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RHS = 1;
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{ Sharp bin boundaries by default }
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JTR = 0;
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{ Default axis orientation (+Y == north) }
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rNx = 0; rNy = 0; rNz = -1;
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Ux = 0; Uy = 1; Uz = 0;
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{ Compute oriented axis angles }
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inc_dz = -Dx*rNx-Dy*rNy-Dz*rNz;
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inc_rx = -RHS*(Dx*(Uy*rNz-Uz*rNy) + Dy*(Uz*rNx-Ux*rNz) + Dz*(Ux*rNy-Uy*rNx));
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inc_ry = Dx*Ux+Dy*Uy+Dz*Uz + inc_dz*(rNx*Ux+rNy*Uy+rNz*Uz);
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r_alt = Asin(inc_dz);
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r_azi = Atan2(inc_rx,inc_ry);
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{ Number of patches per row }
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tnaz(r) : select(r, 30, 30, 24, 24, 18, 12, 6);
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TNR : tnaz(0);
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rnaz(r) = if(r-(MF*TNR-.5), 1, MF*tnaz(floor((r+.5)/MF) + 1));
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alpha = 90/(MF*TNR + .5); { Separation between rows in degrees }
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raccum(r) = if(r-.5, rnaz(r-1) + raccum(r-1), 0);
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{ Random perturbation for final bin # }
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jtr1 = JTR*(.5 - rand(1.958*Dx - 5.386*Dy - 3.772*Dz));
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jtr2 = JTR*(.5 - rand(-6.334*Dx - 2.165*Dy + 7.953*Dz));
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r_row0 = floor(r_alt/alpha);
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r_row = if(JTR, min(max(0,floor(r_alt/alpha + jtr1)),MF*TNR), r_row0);
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r_inc0 = 360/rnaz(r_row0);
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r_inc = 360/rnaz(r_row);
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r_adj = .5*r_inc + if(JTR, jtr2*min(r_inc,r_inc0), 0);
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r_azn = floor( mod(r_azi+r_adj, 360) / r_inc );
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{ Final bin value, -1 for "ground" }
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rbin = if(r_alt, raccum(r_row) + r_azn, -1);
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Nrbins = raccum(MF*TNR+1); { total number of bins }
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