.\" RCSid "$Id: pdfblur.1,v 1.7 2008/11/10 19:08:17 greg Exp $"
.TH PDFBLUR 1 1/24/96 RADIANCE
.SH NAME
pdfblur - generate views for depth-of-field blurring
.SH SYNOPSIS
.B pdfblur
.B aperture
.B nsamp
.B viewfile
.SH DESCRIPTION
.I Pdfblur
takes the given
.I viewfile
and computes
.I nsamp
views based on an aperture diameter of
.I aperture
(in world coordinate units) and a focal distance equal to the length of the
.I \-vd
view direction vector.
When rendered and averaged together, these views will result in
a picture with the specified depth of field.
Either
.I pinterp(1)
or
.I rpict(1)
may be called to do the actual work.
(The given
.I viewfile
must also be passed on the command line to the chosen renderer, since
.I pdfblur
provides supplemental view specifications only.)\0
.PP
For
.I pinterp,
feed the output of
.I pdfblur
to the standard input of
.I pinterp
and apply the
.I \-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
.I \-ff
option together with the
.I \-fr
option of
.I 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
.I \-fr
option will end up recomputing relatively few pixels by
comparison.)\0
.PP
To use
.I pdfblur
with
.I rpict,
apply the
.I \-S
option to indicate a rendering sequence, and set the
.I \-o
option with a formatted file name to save multiple output
pictures.
When all the renderings are finished, combine them with the
.I pcomb(1)
program, using appropriate scalefactors to achieve an average.
Note that using
.I rpict
is MUCH more expensive than using
.I 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).
.PP
For both
.I pinterp
and
.I rpict,
the computation time will be proportional to the number of views from
.I pdfblur.
We have found a
.I nsamp
setting somewhere between 5 and 10 to be adequate for most images.
Relatively larger values are appropriate for larger aperatures.
.PP
The
.I \-pd
option of
.I rpict
may be used instead or in combination with or instead of
.I pdfblur
to blur depth-of-field.
If used in combination,
it is best to set the
.I \-pd
option to the overall
.I aperture
divided by
.I nsamp
to minimize ghosting in the output.
.PP
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.
.SH EXAMPLES
To use
.I pinterp
to simulate an aperture of 0.5 inches on a lens focused at a
distance of 57 inches:
.IP "" .2i
rpict \-vf myview \-x 640 \-y 480 \-z orig.zbf scene.oct > orig.hdr
.br
pdfblur 0.5 57 8 orig.hdr | pinterp \-B \-vf orig.hdr \-x 640 \-y 480
orig.hdr orig.zbf > blurry.hdr
.PP
To use
.I rpict
exclusively to do the same:
.IP "" .2i
pdfblur .5 57 5 myview | rpict \-S 1 \-vf myview \-x 640 \-y 480
\-o view%d.hdr scene.oct
.br
pcomb \-s .2 view1.hdr \-s .2 view2.hdr \-s .2 view3.hdr \-s .2
view4.hdr \-s .2 view5.hdr > blurry.hdr
.SH AUTHOR
Greg Ward
.SH BUGS
This program really only works with perspective views.
.SH "SEE ALSO"
pcomb(1), pinterp(1), pmblur(1), pmdblur(1), rcalc(1), rpict(1), vwright(1)