Revision: | 1.1 |
Committed: | Sat Feb 22 02:07:21 2003 UTC (21 years, 3 months ago) by greg |
Branch: | MAIN |
CVS Tags: | rad5R2, rad4R2P2, rad5R0, rad5R1, rad3R7P2, rad3R7P1, rad4R2, rad4R1, rad4R0, rad3R5, rad3R6, rad3R6P1, rad3R8, rad3R9, rad4R2P1 |
Log Message: | Changes and check-in for 3.5 release Includes new source files and modifications not recorded for many years See ray/doc/notes/ReleaseNotes for notes between 3.1 and 3.5 release |
# | Content |
---|---|
1 | { |
2 | Calculate VL (visibility level) |
3 | |
4 | 5/26/94 |
5 | |
6 | Taken from Bailey, Clear, Berman paper, JIES Summer 1993 |
7 | } |
8 | |
9 | { User must set: |
10 | |
11 | L Adaptation luminance in cd/m^2 |
12 | dL Difference in luminance between background and foreground |
13 | S Target size in minutes of arc |
14 | |
15 | Function computes: |
16 | |
17 | dLt Visible luminance threshold |
18 | Sr Size below which Ricco's law applies |
19 | VL Visibility level |
20 | } |
21 | |
22 | sq(x) : x*x; |
23 | |
24 | fit(a1,a2,n) = a1 * (L^(1/n) + a2)^(n/2); |
25 | |
26 | A = fit(.40743,1.6074,2.8723); |
27 | B = fit(.0840155,.43369,1.7188); |
28 | |
29 | Sr = (4 + 2*L)/(1 + L); |
30 | |
31 | dLt = if(Sr-S, sq(A/S), sq((B*(S-Sr)+A)/S)); |
32 | |
33 | VL = dL / dLt; |