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findglare (1)
NAME
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findglare - locate glare sources in a RADIANCE scene |
SYNOPSIS
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findglare [ -v ][ -ga angles ][ -t
threshold ][ -r resolution ][ -c ][ -p
picture ][ view options ] [[ rtrace options ]
octree ] |
DESCRIPTION
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Findglare locates sources of glare in a specific set
of horizontal directions by computing luminance samples from
a RADIANCE picture and/or octree. Findglare is
intended primarily as a preprocessor for glare calculation
programs such as glarendx(1), and is usually accessed
through the executive script glare(1). |
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If only an octree is given, findglare calls rtrace to
compute the samples it needs. If both an octree and a
picture are specified, findglare calls rtrace only
for samples that are outside the frame of the picture. If
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
-ga option is used -- see below). Note that the
picture file must contain correct view specifications, as
maintained by rpict(1), rview(1), pfilt(1) and
pinterp(1). Specifically, findglare will not
work on pictures processed by pcompos(1) or
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. |
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The output of 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. |
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By default, 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), findglare will substitute the closest
horizontal direction as its view center. The -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: |
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start-end:step
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 findglare will complain if the same angle is given twice either explicitly or implicitly by two ranges. |
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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 -t option. It usually works best to use the 'l'
command within ximage(1) to decide what this value
should be. Alternatively, one can use the 't' command within
rview(1). The idea is to pick a threshold that is
well above the average level but smaller than the source
areas. |
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If the sources in the scene are small, it may be necessary
to increase the default sample resolution of
findglare(1) using the -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 -c flag
should be used to override findglare's default action
of absorbing small sources it deems to be
insignificant. |
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The -v flag switches on verbose mode, where
findglare reports its progress during the
calculation. |
EXAMPLE
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To calculate the glare sources in the image
"scene.pic": |
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findglare -p scene.pic > scene.glr |
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To compute the Guth visual comfort probability from this
result: |
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glarendx -t guth_vcp scene.glr |
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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: |
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findglare -vf good.vp -ga 10-60:10 -av .1 .1 .1 scene.oct
> scene.glr |
AUTHOR
ACKNOWLEDGEMENT
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Work on this program was initiated and sponsored by the LESO
group at EPFL in Switzerland. |
SEE ALSO
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