/usr/share/radiance/rskysrc.cal is in radiance-materials 4R1+20120125-1.
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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 40 41 42 43 44 45 46 47 48 49 50 | { RCSid $Id: rskysrc.cal,v 1.2 2009/07/14 16:16:20 greg Exp $ }
{
Reinhart sky patch positions & solid angles
Greg Ward June 2009
Based on tregsrc.cal
MF controls patch density
Input is Rbin from 1-(144*MF+1) and optional x1 x2 random variables
Output is Dx Dy Dz theta (degree full angle of source)
}
DEGREE : PI/180;
x1 = .5; x2 = .5; { default rand. var. settings for midpoint }
MF : 2^2; { Multiplication factor }
alpha : 90/(MF*7 + .5); { Separation between rows in degrees }
{ Number of patches per row }
tnaz(r) : select(r, 30, 30, 24, 24, 18, 12, 6);
rnaz(r) : if(r-(7*MF-.5), 1, MF*tnaz(floor((r+.5)/MF) + 1));
raccum(r) : if(r-.5, rnaz(r-1) + raccum(r-1), 0);
RowMax : 7*MF + 1;
Rmax : raccum(RowMax);
Rfindrow(r, rem) : if(rem-rnaz(r)-.5, Rfindrow(r+1, rem-rnaz(r)), r);
Rrow = if(Rbin-(Rmax-.5), RowMax, Rfindrow(0, Rbin));
Rcol = Rbin - raccum(Rrow) - 1;
Razi_width = 2*PI / rnaz(Rrow);
RAH : alpha*DEGREE;
Razi = (Rcol + x2 - .5)*Razi_width;
Ralt = (Rrow + x1)*RAH;
Romega = if(Rmax-.5-Rbin,
Razi_width*(sin(RAH*(Rrow+1)) - sin(RAH*Rrow)),
2*PI*(1 - cos(RAH/2)) );
cos_ralt = cos(Ralt);
Dx = sin(Razi)*cos_ralt;
Dy = cos(Razi)*cos_ralt;
Dz = sin(Ralt);
theta = 2/DEGREE * acos(1 - Romega/(2*PI));
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