| 1 |
.\" RCSid "$Id: findglare.1,v 1.4 2007/09/04 17:36:40 greg Exp $" |
| 2 |
.TH FINDGLARE 1 11/15/93 RADIANCE |
| 3 |
.SH NAME |
| 4 |
findglare - locate glare sources in a RADIANCE scene |
| 5 |
.SH SYNOPSIS |
| 6 |
.B findglare |
| 7 |
[ |
| 8 |
.B \-v |
| 9 |
][ |
| 10 |
.B "\-ga angles" |
| 11 |
][ |
| 12 |
.B "\-t threshold" |
| 13 |
][ |
| 14 |
.B "\-r resolution" |
| 15 |
][ |
| 16 |
.B \-c |
| 17 |
][ |
| 18 |
.B "\-p picture" |
| 19 |
][ |
| 20 |
view options |
| 21 |
] [[ |
| 22 |
rtrace options |
| 23 |
] |
| 24 |
.B octree |
| 25 |
] |
| 26 |
.SH DESCRIPTION |
| 27 |
.I Findglare |
| 28 |
locates sources of glare in a specific set of horizontal directions |
| 29 |
by computing luminance samples from a RADIANCE picture and/or octree. |
| 30 |
.I Findglare |
| 31 |
is intended primarily as a preprocessor for glare calculation |
| 32 |
programs such as |
| 33 |
.I glarendx(1), |
| 34 |
and is usually accessed through the executive script |
| 35 |
.I glare(1). |
| 36 |
.PP |
| 37 |
If only an octree is given, |
| 38 |
.I findglare |
| 39 |
calls rtrace to compute the samples it needs. |
| 40 |
If both an octree and a picture are specified, |
| 41 |
.I findglare |
| 42 |
calls rtrace only for samples that are outside the frame of |
| 43 |
the picture. |
| 44 |
If |
| 45 |
.I findglare |
| 46 |
does not have an octree and the picture does not completely cover |
| 47 |
the area of interest, a warning will be issued and everything |
| 48 |
outside the picture will be treated as if it were black. |
| 49 |
It is preferable to use a picture with a fisheye view |
| 50 |
and a horizontal and vertical size of at least 180 degrees (more |
| 51 |
horizontally if the |
| 52 |
.I \-ga |
| 53 |
option is used -- see below). |
| 54 |
Note that the picture file must contain correct view specifications, |
| 55 |
as maintained by |
| 56 |
.I rpict(1), |
| 57 |
.I rvu(1), |
| 58 |
.I pfilt(1) |
| 59 |
and |
| 60 |
.I pinterp(1). |
| 61 |
Specifically, |
| 62 |
.I findglare |
| 63 |
will not work on pictures processed by |
| 64 |
.I pcompos(1) |
| 65 |
or |
| 66 |
.I pcomb(1). |
| 67 |
It is also essential to give the proper rtrace options when an |
| 68 |
octree is used so that the calculated luminance values are correct. |
| 69 |
.PP |
| 70 |
The output of |
| 71 |
.I findglare |
| 72 |
is a list of glare source directions, solid angles and average |
| 73 |
luminances, plus a list of indirect vertical illuminance values |
| 74 |
as a function of angle. |
| 75 |
Angles are measured in degrees from the view center, |
| 76 |
with positive angles to the left and negative angles to the right. |
| 77 |
.PP |
| 78 |
By default, |
| 79 |
.I findglare |
| 80 |
only computes glare sources and indirect vertical illuminance |
| 81 |
for the given view (taken from the picture if none is specified). |
| 82 |
If the view direction is not horizontal to begin with |
| 83 |
(ie. perpendicular to the view up vector), |
| 84 |
.I findglare |
| 85 |
will substitute the closest horizontal direction as its view |
| 86 |
center. |
| 87 |
The |
| 88 |
.I \-ga |
| 89 |
option can be used to specify a set of directions to consider |
| 90 |
about the center of view. |
| 91 |
This specification is given by a starting angle, ending angle, and |
| 92 |
step angle like so: |
| 93 |
.nf |
| 94 |
start-end:step |
| 95 |
.fi |
| 96 |
All angles must be whole degrees within the range 1 to 180. |
| 97 |
Multiple angle ranges may be separated by commas, and individual |
| 98 |
angles may be given without the ending and step angles. |
| 99 |
Note that |
| 100 |
.I findglare |
| 101 |
will complain if the same angle is given twice either explicitly |
| 102 |
or implicitly by two ranges. |
| 103 |
.PP |
| 104 |
.I Findglare |
| 105 |
normally identifies glare sources as directions that are |
| 106 |
brighter than 7 times the average luminance level. |
| 107 |
It is possible to override this determination by giving an |
| 108 |
explicit luminance threshold with the |
| 109 |
.I \-t |
| 110 |
option. |
| 111 |
It usually works best to use the 'l' command within |
| 112 |
.I ximage(1) |
| 113 |
to decide what this value should be. |
| 114 |
Alternatively, one can use the 't' command within |
| 115 |
.I rvu(1). |
| 116 |
The idea is to pick a threshold that is well above the average level |
| 117 |
but smaller than the source areas. |
| 118 |
.PP |
| 119 |
If the sources in the scene are small, it may be necessary to |
| 120 |
increase the default sample resolution of |
| 121 |
.I findglare(1) |
| 122 |
using the |
| 123 |
.I \-r |
| 124 |
option. |
| 125 |
The default resolution is 150 vertical samples and a proportional number |
| 126 |
of horizontal samples. |
| 127 |
If besides being small, the sources are not much brighter than the |
| 128 |
threshold, the |
| 129 |
.I \-c |
| 130 |
flag should be used to override |
| 131 |
.I findglare's |
| 132 |
default action of absorbing small sources it deems to be |
| 133 |
insignificant. |
| 134 |
.PP |
| 135 |
The |
| 136 |
.I \-v |
| 137 |
flag switches on verbose mode, where |
| 138 |
.I findglare |
| 139 |
reports its progress during the calculation. |
| 140 |
.SH EXAMPLE |
| 141 |
To calculate the glare sources in the image "scene.hdr": |
| 142 |
.IP "" .2i |
| 143 |
findglare \-p scene.hdr > scene.glr |
| 144 |
.PP |
| 145 |
To compute the Guth visual comfort probability from this result: |
| 146 |
.IP "" .2i |
| 147 |
glarendx \-t guth_vcp scene.glr |
| 148 |
.PP |
| 149 |
To compute the glare for a set of angles around the view "good.vp" |
| 150 |
from the octree "scene.oct" using an ambient level of .1: |
| 151 |
.IP "" .2i |
| 152 |
findglare \-vf good.vp \-ga 10-60:10 \-av .1 .1 .1 scene.oct > scene.glr |
| 153 |
.SH AUTHOR |
| 154 |
Greg Ward |
| 155 |
.SH ACKNOWLEDGEMENT |
| 156 |
Work on this program was initiated and sponsored by the LESO |
| 157 |
group at EPFL in Switzerland. |
| 158 |
.SH "SEE ALSO" |
| 159 |
getinfo(1), glare(1), glarendx(1), pfilt(1), rpict(1), rtrace(1), |
| 160 |
rvu(1), xglaresrc(1), ximage(1) |
