Radiance findglare program

FINDGLARE(1)                                                      FINDGLARE(1)

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  sam-
       ples  it  needs.   If both an octree and a picture are specified, find-
       glare 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 pic-
       tures  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  cal-
       culated 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 illumi-
       nance  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 spec-
       ified).   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 implic-
       itly 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)

RADIANCE                           11/15/93                       FINDGLARE(1)