Radiance mkillum program



MKILLUM(1)                                                          MKILLUM(1)




NAME

       mkillum - compute illum sources for a RADIANCE scene


SYNOPSIS

       mkillum [ -n nprocs ][ rtrace options ] octree [ < file .. ]
       mkillum [ rtrace options ] -defaults


DESCRIPTION

       Mkillum  takes  a prepared RADIANCE scene description and an octree and
       computes light source distributions for each  surface,  replacing  them
       with  secondary  sources whose contributions can be computed more effi-
       ciently by rpict(1) and rvu(1).  This type of optimization is most use-
       ful  for  windows and skylights which represent concentrated sources of
       indirect illumination.  Mkillum  is  not  appropriate  for  very  large
       sources  or  sources  with highly directional distributions.  These are
       best handled respectively by the ambient calculation and the  secondary
       source types in RADIANCE.

       If  the  -n  option  is specified with a value greater than 1, multiple
       rtrace(1) processes will be used to accelerate computation on a  shared
       memory  machine.  Note that there is no benefit to using more processes
       than there are local CPUs available to do the work.

       Remaining arguments to mkillum are passed directly to rtrace(1),  which
       is  used  to  compute  the  light distributions for the input surfaces.
       These surfaces can be any combination of polygons, spheres  and  rings.
       Other  surfaces  may be included, but mkillum cannot compute their dis-
       tributions.

       By default, mkillum reads from its standard input  and  writes  to  its
       standard  output.   It is possible to specify multiple input files in a
       somewhat unconventional fashion by placing a lesser-than  symbol  ('<')
       before  the file names.  (Note that this character must be escaped from
       most shells.)  This is necessary so mkillum can tell  where  the  argu-
       ments to rtrace(1) end and its own input files begin.


VARIABLES

       Mkillum  has  a number of parameters that can be changed by comments in
       the input file of the form:

            #@mkillum variable=value option switch{+|-} ..

       String or integer variables are separated  from  their  values  by  the
       equals  sign  ('=').   Options appear by themselves.  Switches are fol-
       lowed either by a plus sign to turn them on or a  minus  sign  to  turn
       them off.

       Parameters are usually changed many times within the same input file to
       tailor the calculation, specify different labels and so on.  The param-
       eters and their meanings are described below.

       o=string  Set  the  output  file  to string.  All subsequent scene data
                 will be sent to this file.  If this appears in the first com-
                 ment  in the input, nothing will be sent to the standard out-
                 put.  Note that this is not recommended when running  mkillum
                 from  rad(1),  which expects the output to be on the standard
                 output.

       m=string  Set the material identifier to string.   This  name  will  be
                 used  not  only as the new surface modifier, but it will also
                 be used to name the distribution pattern and the data  files.
                 The distribution name will be string plus the suffix ".dist".
                 The data file will be named string plus possibly  an  integer
                 plus  a  ".dat"  suffix.   The integer is used to avoid acci-
                 dently writing over an existing  file.   If  overwriting  the
                 file is desired, use the f variable below.

       f=string  Set the data file name to string.  The next data file will be
                 given this name plus a ".dat" suffix.  Subsequent files  will
                 be  named  string plus an integer plus the ".dat" suffix.  An
                 existing file with the same name  will  be  clobbered.   This
                 variable  may  be  unset by leaving off the value.  (See also
                 the m variable above.)

       a         Produce secondary sources for all  of  the  surfaces  in  the
                 input.  This is the default.

       e=string  Produce secondary sources for all surfaces except those modi-
                 fied by string.  Surfaces modified by string will  be  passed
                 to the output unchanged.

       i=string  Only  produce  secondary  sources  for  surfaces  modified by
                 string.

       n         Do not produce any secondary  sources.   All  input  will  be
                 passed to the output unaffected.

       b=real    Do  not produce a secondary source for a surface if its aver-
                 age brightness (radiance) is less than the value real.

       c={d|a|n} Use color information according to the given  character.   If
                 the  character  is  d, then color information will be used in
                 three separate data files and the distribution will be  fully
                 characterized in terms of color.  If the character is a, then
                 only the average color is computed and the distribution  will
                 not  contain  color information.  If the character is n, even
                 the average distribution color will be thrown away, producing
                 secondary sources that are completely uncolored.  This may be
                 desirable from a color-balancing point of view.

       d=integer Set the number of direction samples per  projected  steradian
                 to  integer.   The number of directions stored in the associ-
                 ated data file will be approximately this  number  multiplied
                 by  pi  for  polygons  and rings, and by 4pi for spheres.  If
                 integer is zero, then a diffuse source is assumed and no dis-
                 tribution is created.

       s=integer Set the number of ray samples per direction to integer.  This
                 variable affects the accuracy of the distribution  value  for
                 each direction as well as the computation time for mkillum.

       l{+|-}    Switch  between  light  sources  and  illum sources.  If this
                 switch is enabled (l+), mkillum will use  the  material  type
                 "light"  to  represent  surfaces.   If disabled (l-), mkillum
                 will use the material type "illum"  with  the  input  surface
                 modifier as its alternate material.  The default is l-.


EXAMPLES

       The  following  command  generates illum's corresponding to geometry in
       the files "it1.rad" and "it2.rad":

          mkillum -ab 2 -ad 1024 -av .1 .1 .1 basic.oct "<" it1.rad it2.rad  >
          illums.rad

       The  output  file "illums.rad" would then be combined with the original
       scene geometry to create a more easily rendered composite.


AUTHOR

       Greg Ward


ACKNOWLEDGEMENT

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


SEE ALSO

       oconv(1), rad(1), rpict(1), rtrace(1), rvu(1)



RADIANCE                            10/6/95                         MKILLUM(1)

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