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)