FINDGLARE(1)                                                      FINDGLARE(1)



NNAAMMEE
       findglare - locate glare sources in a RADIANCE scene

SSYYNNOOPPSSIISS
       ffiinnddggllaarree  [ --vv ][ --ggaa aanngglleess ][ --tt tthhrreesshhoolldd ][ --rr rreessoolluuttiioonn ][ --cc ][
       --pp ppiiccttuurree ][ view options ] [[ rtrace options ] ooccttrreeee ]

DDEESSCCRRIIPPTTIIOONN
       _F_i_n_d_g_l_a_r_e locates sources of glare in  a  specific  set  of  horizontal
       directions  by  computing  luminance  samples  from  a RADIANCE picture
       and/or octree.  _F_i_n_d_g_l_a_r_e is intended primarily as a  preprocessor  for
       glare calculation programs such as _g_l_a_r_e_n_d_x_(_1_)_, and is usually accessed
       through the executive script _g_l_a_r_e_(_1_)_.

       If only an octree is given, _f_i_n_d_g_l_a_r_e calls rtrace to compute the  sam-
       ples  it  needs.   If both an octree and a picture are specified, _f_i_n_d_-
       _g_l_a_r_e calls rtrace only for samples that are outside the frame  of  the
       picture.  If _f_i_n_d_g_l_a_r_e 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 _-_g_a
       option is used -- see below).  Note that the picture file must  contain
       correct   view  specifications,  as  maintained  by  _r_p_i_c_t_(_1_)_,  _r_v_u_(_1_)_,
       _p_f_i_l_t_(_1_) and _p_i_n_t_e_r_p_(_1_)_.  Specifically, _f_i_n_d_g_l_a_r_e will not work on pic-
       tures  processed  by  _p_c_o_m_p_o_s_(_1_)  or _p_c_o_m_b_(_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  _f_i_n_d_g_l_a_r_e  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, _f_i_n_d_g_l_a_r_e 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),  _f_i_n_d_g_l_a_r_e  will  substitute  the
       closest horizontal direction as its view center.  The _-_g_a 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  _f_i_n_d_g_l_a_r_e  will
       complain  if the same angle is given twice either explicitly or implic-
       itly by two ranges.

       _F_i_n_d_g_l_a_r_e 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 _x_i_m_a_g_e_(_1_) to decide what this value should  be.   Alternatively,
       one  can  use  the  't'  command  within _r_v_u_(_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 _f_i_n_d_g_l_a_r_e_(_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
       _f_i_n_d_g_l_a_r_e_'_s default action of absorbing small sources it  deems  to  be
       insignificant.

       The  _-_v  flag  switches  on  verbose  mode, where _f_i_n_d_g_l_a_r_e reports its
       progress during the calculation.

EEXXAAMMPPLLEE
       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

AAUUTTHHOORR
       Greg Ward

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

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



RADIANCE                           11/15/93                       FINDGLARE(1)
