NAME

       pdfblur - generate views for depth-of-field blurring

SYNOPSIS

       pdfblur aperture nsamp viewfile

DESCRIPTION

       Pdfblur  takes  the given viewfile and computes nsamp views based on an aperture diameter of aperture (in
       world coordinate units) and a focal distance equal to the length of the -vd view direction vector.   When
       rendered  and  averaged together, these views will result in a picture with the specified depth of field.
       Either pinterp(1) or rpict(1) may be called to do the actual work.  (The  given  viewfile  must  also  be
       passed   on  the  command  line  to  the  chosen  renderer,  since  pdfblur  provides  supplemental  view
       specifications only.)

       For pinterp, feed the output of pdfblur to the standard input of pinterp and apply the -B option to  blur
       views  together.   In  most  cases,  a  single  picture  with  z-buffer  is all that is required to get a
       satisfactory result, though the perfectionist may wish to apply three pictures  arranged  in  a  triangle
       about the aperature, or alternatively apply the -ff option together with the -fr option of pinterp.  (The
       latter  may  actually  work  out to be faster, since rendering three views takes three times as long as a
       single view, and the -fr option will end up recomputing relatively few pixels by comparison.)

       To use pdfblur with rpict, apply the -S option to indicate a rendering sequence, and set  the  -o  option
       with  a  formatted  file  name  to  save multiple output pictures.  When all the renderings are finished,
       combine them with the pcomb(1) program, using appropriate scalefactors to achieve an average.  Note  that
       using  rpict  is  MUCH  more  expensive  than  using pinterp, and it is only recommended if the scene and
       application absolutely demand it (e.g. there is prominent refraction that must be modeled accurately).

       For both pinterp and rpict, the computation time will  be  proportional  to  the  number  of  views  from
       pdfblur.   We  have  found  a  nsamp  setting  somewhere between 5 and 10 to be adequate for most images.
       Relatively larger values are appropriate for larger aperatures.

       The -pd option of rpict may be used instead or in combination with or instead of pdfblur to  blur  depth-
       of-field.   If  used  in combination, it is best to set the -pd option to the overall aperture divided by
       nsamp to minimize ghosting in the output.

       To simulate a particular camera's aperture, divide the focal length of the lens  by  the  f-number,  then
       convert to the corresponding world coordinate units.  For example, if you wish to simulate a 50mm lens at
       f/2.0  in  a  scene  modeled  in meters, then you divide 50mm by 2.0 to get 25mm, which corresponds to an
       effective aperture of 0.025 meters.

EXAMPLES

       To use pinterp to simulate an aperture of 0.5 inches on a lens focused at a distance of 57 inches:

         rpict -vf myview -x 640 -y 480 -z orig.zbf scene.oct > orig.hdr
         pdfblur 0.5 57 8 orig.hdr | pinterp -B -vf orig.hdr -x 640 -y 480 orig.hdr orig.zbf > blurry.hdr

       To use rpict exclusively to do the same:

         pdfblur .5 57 5 myview | rpict -S 1 -vf myview -x 640 -y 480 -o view%d.hdr scene.oct
         pcomb -s .2 view1.hdr -s .2 view2.hdr -s .2 view3.hdr -s .2 view4.hdr -s .2 view5.hdr > blurry.hdr

AUTHOR

       Greg Ward

BUGS

       This program really only works with perspective views.

SEE ALSO

       pcomb(1), pinterp(1), pmblur(1), pmdblur(1), rcalc(1), rpict(1), vwright(1)

RADIANCE                                             1/24/96                                          PDFBLUR(1)