| Revision: | 1.1 |
| Committed: | Sat Feb 22 02:07:21 2003 UTC (21 years, 2 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 |
| # | User | Rev | Content |
|---|---|---|---|
| 1 | greg | 1.1 | { |
| 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; |