man/man1/findglare.1

.\" RCSid "$Id: findglare.1,v 1.4 2007/09/04 17:36:40 greg Exp $"
.TH FINDGLARE 1 11/15/93 RADIANCE
.SH NAME
findglare - locate glare sources in a RADIANCE scene
.SH SYNOPSIS
.B findglare
[
.B \-v
][
.B "\-ga angles"
][
.B "\-t threshold"
][
.B "\-r resolution"
][
.B \-c
][
.B "\-p picture"
][
view options
] [[
rtrace options
]
.B octree
]
.SH DESCRIPTION
.I Findglare
locates sources of glare in a specific set of horizontal directions
by computing luminance samples from a RADIANCE picture and/or octree.
.I Findglare
is intended primarily as a preprocessor for glare calculation
programs such as
.I glarendx(1),
and is usually accessed through the executive script
.I glare(1).
.PP
If only an octree is given,
.I findglare
calls rtrace to compute the samples it needs.
If both an octree and a picture are specified,
.I findglare
calls rtrace only for samples that are outside the frame of
the picture.
If 
.I findglare
does not have an octree and the picture does not completely cover
the area of interest, a warning will be issued and everything
outside the picture will be treated as if it were black.
It is preferable to use a picture with a fisheye view
and a horizontal and vertical size of at least 180 degrees (more
horizontally if the
.I \-ga
option is used -- see below).
Note that the picture file must contain correct view specifications,
as maintained by
.I rpict(1),
.I rvu(1),
.I pfilt(1)
and
.I pinterp(1).
Specifically,
.I findglare
will not work on pictures processed by
.I pcompos(1)
or
.I pcomb(1).
It is also essential to give the proper rtrace options when an
octree is used so that the calculated luminance values are correct.
.PP
The output of
.I findglare
is a list of glare source directions, solid angles and average
luminances, plus a list of indirect vertical illuminance values
as a function of angle.
Angles are measured in degrees from the view center,
with positive angles to the left and negative angles to the right.
.PP
By default,
.I findglare
only computes glare sources and indirect vertical illuminance
for the given view (taken from the picture if none is specified).
If the view direction is not horizontal to begin with
(ie. perpendicular to the view up vector),
.I findglare
will substitute the closest horizontal direction as its view
center.
The
.I \-ga
option can be used to specify a set of directions to consider
about the center of view.
This specification is given by a starting angle, ending angle, and
step angle like so:
.nf
        start-end:step
.fi
All angles must be whole degrees within the range 1 to 180.
Multiple angle ranges may be separated by commas, and individual
angles may be given without the ending and step angles.
Note that
.I findglare
will complain if the same angle is given twice either explicitly
or implicitly by two ranges.
.PP
.I Findglare
normally identifies glare sources as directions that are
brighter than 7 times the average luminance level.
It is possible to override this determination by giving an
explicit luminance threshold with the
.I \-t
option.
It usually works best to use the 'l' command within
.I ximage(1)
to decide what this value should be.
Alternatively, one can use the 't' command within
.I rvu(1).
The idea is to pick a threshold that is well above the average level
but smaller than the source areas.
.PP
If the sources in the scene are small, it may be necessary to
increase the default sample resolution of
.I findglare(1)
using the
.I \-r
option.
The default resolution is 150 vertical samples and a proportional number
of horizontal samples.
If besides being small, the sources are not much brighter than the
threshold, the
.I \-c
flag should be used to override
.I findglare's
default action of absorbing small sources it deems to be
insignificant.
.PP
The
.I \-v
flag switches on verbose mode, where
.I findglare
reports its progress during the calculation.
.SH EXAMPLE
To calculate the glare sources in the image "scene.hdr":
.IP "" .2i
findglare \-p scene.hdr > scene.glr
.PP
To compute the Guth visual comfort probability from this result:
.IP "" .2i
glarendx \-t guth_vcp scene.glr
.PP
To compute the glare for a set of angles around the view "good.vp"
from the octree "scene.oct" using an ambient level of .1:
.IP "" .2i
findglare \-vf good.vp \-ga 10-60:10 \-av .1 .1 .1 scene.oct > scene.glr
.SH AUTHOR
Greg Ward
.SH ACKNOWLEDGEMENT
Work on this program was initiated and sponsored by the LESO
group at EPFL in Switzerland.
.SH "SEE ALSO"
getinfo(1), glare(1), glarendx(1), pfilt(1), rpict(1), rtrace(1),
rvu(1), xglaresrc(1), ximage(1)
Revision:	1.5
Committed:	Mon Nov 10 19:08:17 2008 UTC (16 years, 5 months ago) by greg
Branch:	MAIN
CVS Tags:	rad5R4, rad5R2, rad4R2P2, rad5R0, rad5R1, rad4R2, rad4R1, rad4R0, rad4R2P1, rad5R3, HEAD
Changes since 1.4:	+3 -3 lines
Log Message:	Changed ".pic" extension to ".hdr" throughout
#	User	Rev	Content
1	greg	1.5	.\" RCSid "$Id: findglare.1,v 1.4 2007/09/04 17:36:40 greg Exp $"
2	greg	1.1	.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	greg	1.3	.I rvu(1),
58	greg	1.1	.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	greg	1.3	.I rvu(1).
116	greg	1.1	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	greg	1.5	To calculate the glare sources in the image "scene.hdr":
142	greg	1.1	.IP "" .2i
143	greg	1.5	findglare \-p scene.hdr > scene.glr
144	greg	1.1	.PP
145			To compute the Guth visual comfort probability from this result:
146			.IP "" .2i
147	greg	1.4	glarendx \-t guth_vcp scene.glr
148	greg	1.1	.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	greg	1.4	findglare \-vf good.vp \-ga 10-60:10 \-av .1 .1 .1 scene.oct > scene.glr
153	greg	1.1	.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	greg	1.3	rvu(1), xglaresrc(1), ximage(1)