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root/radiance/ray/src/cal/cal/tregenza.cal
Revision: 1.4
Committed: Tue Sep 15 00:17:36 2009 UTC (14 years, 6 months ago) by greg
Branch: MAIN
CVS Tags: rad5R4, rad5R2, rad4R2P2, rad5R0, rad5R1, rad4R2, rad4R1, rad4R0, rad4R2P1, rad5R3, HEAD
Changes since 1.3: +2 -2 lines
Log Message:
Better fix to over-range condition

File Contents

# Content
1 { RCSid $Id: tregenza.cal,v 1.3 2009/07/02 21:44:33 greg Exp $ }
2 {
3 Compute bin numbers corresponding to Tregenza sky discretization
4
5 The Tregenza sky uses 145 patches, with patch 1 pointing due
6 North at the horizon, and continuing around to the East to
7 patch 30, which comprises the first altitude row (alt = 6 degrees).
8 Each successive row increases altitude by 12 degrees, with the
9 final altitude at the zenith (90 degrees). Azimuth is evenly
10 divided among 30, 30, 24, 24, 18, 12, 6, and 1 divisions per row.
11
12 In addition to the bin numbers 1-145 corresponding to this
13 standard, bin 0 is used for the ground plane (altitude < 0).
14
15 Input is normalized ray direction (Dx,Dy,Dz). The Y-axis is
16 assumed to point North, and the X-axis East, matching the
17 convention set by gensky(1).
18
19 Greg Ward May 2005
20 }
21 DEGREE : PI/180;
22 Asin(x) : if(x-1, PI/2, if(-1-x, -PI/2, asin(x)));
23 posangle(a) : if(-a, a + 2*PI, a);
24 Atan2(y,x) : posangle(atan2(y,x));
25
26 alt = Asin(Dz)/DEGREE;
27 azi = Atan2(Dx,Dy)/DEGREE;
28
29 tazi(inc) = if(359.9999-.5*inc - azi, floor((azi+.5*inc)/inc), 0);
30
31 tbin = if(-alt, 0,
32 select(floor(alt/12) + 1,
33 1 + tazi(12),
34 31 + tazi(12),
35 61 + tazi(15),
36 85 + tazi(15),
37 109 + tazi(20),
38 127 + tazi(30),
39 139 + tazi(60),
40 145
41 ) );
42
43 Ntbins : 146; { total number of bins }