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root/radiance/ray/src/cv/source.cal
Revision: 2.5
Committed: Wed Feb 24 10:24:58 1993 UTC (31 years, 1 month ago) by greg
Branch: MAIN
Changes since 2.4: +4 -1 lines
Log Message:
added additional comments about the box correction functions

File Contents

# Content
1 { SCCSid "$SunId$ LBL" }
2
3 {
4 Source distribution coordinates (degrees).
5
6 Theta is measured from the negative z-axis,
7 phi is measured from the positive x-axis
8 according to the right-hand rule.
9
10 srcB_vert and srcB_horiz are angles
11 used in type B photometry.
12
13 boxcorr function corrects for distribution modeled
14 with a rectangular box. lboxcorr provides a more
15 accurate calculation for nearby surfaces, but requires
16 that the source box be centered at the origin.
17 The dimensions of the box, which must be aligned with
18 the x,y,z axes, are given in meters regardless of the
19 units being used in the scene file.
20
21 A1 - optional multipier
22 A2,A3,A4 - X,Y,Z dimensions of axis-aligned box (in meters!)
23 }
24 { local definitions }
25 boxprojection = abs(Dx)*A3*A4 + abs(Dy)*A2*A4 + abs(Dz)*A2*A3;
26 lboxprojection = ( noneg(abs(Px-Dx*Ts)-A2/2)*A3*A4 +
27 noneg(abs(Py-Dy*Ts)-A3/2)*A2*A4 +
28 noneg(abs(Pz-Dz*Ts)-A4/2)*A2*A3 ) / Ts;
29
30 flatcorr(v) = corr(v) / Rdot; { correction for flat sources }
31 corr(v) = if(AC-.5, A1*v, v); { multiplier correction }
32 boxcorr(v) = A1 * v / boxprojection; { correction for emitting box }
33 lboxcorr(v) = A1 * v / lboxprojection; { local box correction }
34
35 src_theta = Acos(Dz) / DEGREE; { 0-180 }
36 src_phi = mod( atan2(Dy, Dx) / DEGREE, 360 ); { 0-360 }
37 { bilateral symmetry }
38 src_phi2 = tri( src_phi, 180 ); { 0-180 }
39 { quadrilateral symmetry }
40 src_phi4 = tri( src_phi, 90 ); { 0-90 }
41
42 { Type B photometry coordinates }
43 srcB_vert = atan( -Dx/Dz ) / DEGREE;
44 srcB_horiz = Asin(Dy) / DEGREE;
45 { w/ symmetry }
46 srcB_vert2 = abs( srcB_vert );
47 srcB_horiz2 = abs( srcB_horiz );