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.\" RCSid "$Id: findglare.1,v 1.3 2004/01/01 19:31:44 greg Exp $" |
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.TH FINDGLARE 1 11/15/93 RADIANCE |
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.SH NAME |
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findglare - locate glare sources in a RADIANCE scene |
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.SH SYNOPSIS |
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.B findglare |
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[ |
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.B \-v |
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][ |
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.B "\-ga angles" |
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][ |
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.B "\-t threshold" |
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][ |
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.B "\-r resolution" |
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][ |
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.B \-c |
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][ |
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.B "\-p picture" |
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][ |
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view options |
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] [[ |
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rtrace options |
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] |
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.B octree |
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] |
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.SH DESCRIPTION |
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.I Findglare |
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locates sources of glare in a specific set of horizontal directions |
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by computing luminance samples from a RADIANCE picture and/or octree. |
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.I Findglare |
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is intended primarily as a preprocessor for glare calculation |
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programs such as |
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.I glarendx(1), |
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and is usually accessed through the executive script |
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.I glare(1). |
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.PP |
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If only an octree is given, |
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.I findglare |
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calls rtrace to compute the samples it needs. |
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If both an octree and a picture are specified, |
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.I findglare |
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calls rtrace only for samples that are outside the frame of |
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the picture. |
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If |
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.I findglare |
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does not have an octree and the picture does not completely cover |
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the area of interest, a warning will be issued and everything |
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outside the picture will be treated as if it were black. |
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It is preferable to use a picture with a fisheye view |
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and a horizontal and vertical size of at least 180 degrees (more |
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horizontally if the |
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.I \-ga |
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option is used -- see below). |
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Note that the picture file must contain correct view specifications, |
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as maintained by |
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.I rpict(1), |
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.I rvu(1), |
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.I pfilt(1) |
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and |
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.I pinterp(1). |
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Specifically, |
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.I findglare |
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will not work on pictures processed by |
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.I pcompos(1) |
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or |
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.I pcomb(1). |
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It is also essential to give the proper rtrace options when an |
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octree is used so that the calculated luminance values are correct. |
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.PP |
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The output of |
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.I findglare |
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is a list of glare source directions, solid angles and average |
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luminances, plus a list of indirect vertical illuminance values |
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as a function of angle. |
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Angles are measured in degrees from the view center, |
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with positive angles to the left and negative angles to the right. |
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.PP |
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By default, |
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.I findglare |
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only computes glare sources and indirect vertical illuminance |
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for the given view (taken from the picture if none is specified). |
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If the view direction is not horizontal to begin with |
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(ie. perpendicular to the view up vector), |
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.I findglare |
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will substitute the closest horizontal direction as its view |
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center. |
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The |
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.I \-ga |
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option can be used to specify a set of directions to consider |
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about the center of view. |
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This specification is given by a starting angle, ending angle, and |
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step angle like so: |
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.nf |
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start-end:step |
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.fi |
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All angles must be whole degrees within the range 1 to 180. |
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Multiple angle ranges may be separated by commas, and individual |
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angles may be given without the ending and step angles. |
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Note that |
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.I findglare |
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will complain if the same angle is given twice either explicitly |
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or implicitly by two ranges. |
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.PP |
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.I Findglare |
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normally identifies glare sources as directions that are |
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brighter than 7 times the average luminance level. |
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It is possible to override this determination by giving an |
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explicit luminance threshold with the |
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.I \-t |
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option. |
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It usually works best to use the 'l' command within |
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.I ximage(1) |
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to decide what this value should be. |
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Alternatively, one can use the 't' command within |
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.I rvu(1). |
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The idea is to pick a threshold that is well above the average level |
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but smaller than the source areas. |
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.PP |
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If the sources in the scene are small, it may be necessary to |
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increase the default sample resolution of |
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.I findglare(1) |
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using the |
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.I \-r |
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option. |
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The default resolution is 150 vertical samples and a proportional number |
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of horizontal samples. |
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If besides being small, the sources are not much brighter than the |
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threshold, the |
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.I \-c |
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flag should be used to override |
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.I findglare's |
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default action of absorbing small sources it deems to be |
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insignificant. |
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.PP |
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The |
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.I \-v |
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flag switches on verbose mode, where |
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.I findglare |
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reports its progress during the calculation. |
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.SH EXAMPLE |
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To calculate the glare sources in the image "scene.pic": |
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.IP "" .2i |
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findglare \-p scene.pic > scene.glr |
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.PP |
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To compute the Guth visual comfort probability from this result: |
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.IP "" .2i |
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glarendx \-t guth_vcp scene.glr |
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.PP |
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To compute the glare for a set of angles around the view "good.vp" |
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from the octree "scene.oct" using an ambient level of .1: |
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.IP "" .2i |
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findglare \-vf good.vp \-ga 10-60:10 \-av .1 .1 .1 scene.oct > scene.glr |
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.SH AUTHOR |
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Greg Ward |
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.SH ACKNOWLEDGEMENT |
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Work on this program was initiated and sponsored by the LESO |
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group at EPFL in Switzerland. |
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.SH "SEE ALSO" |
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getinfo(1), glare(1), glarendx(1), pfilt(1), rpict(1), rtrace(1), |
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rvu(1), xglaresrc(1), ximage(1) |
