NAME

       findglare - locate glare sources in a RADIANCE scene

SYNOPSIS

       findglare  [ -v ][ -ga angles ][ -t threshold ][ -r resolution ][ -c ][ -p picture ][ view
       options ] [[ rtrace options ] octree ]

DESCRIPTION

       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).

       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), rvu(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.

       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.

       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:
            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.

       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 rvu(1).  The idea is to pick a threshold that  is  well  above  the
       average level but smaller than the source areas.

       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.

       The  -v  flag  switches  on  verbose mode, where findglare reports its progress during the
       calculation.

EXAMPLE

       To calculate the glare sources in the image "scene.hdr":

         findglare -p scene.hdr > scene.glr

       To compute the Guth visual comfort probability from this result:

         glarendx -t guth_vcp scene.glr

       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:

         findglare -vf good.vp -ga 10-60:10 -av .1 .1 .1 scene.oct > scene.glr

AUTHOR

       Greg Ward

ACKNOWLEDGEMENT

       Work on this program was initiated and sponsored by the LESO group at EPFL in Switzerland.

SEE ALSO

       getinfo(1),  glare(1),  glarendx(1),  pfilt(1), rpict(1), rtrace(1), rvu(1), xglaresrc(1),
       ximage(1)