.\" RCSid "$Id: pmdblur.1,v 1.4 2008/11/10 19:08:17 greg Exp $"
.TH PMDBLUR 1 1/17/05 RADIANCE
.SH NAME
pmdblur - generate views for combined camera motion and depth blurring
.SH SYNOPSIS
.B pmdblur
.B speed
.B aperture
.B nsamp
.B v0file
.B v1file
.SH DESCRIPTION
.I Pmdblur
takes two viewfiles and generates
.I nsamp
views starting from
.I v0file
and moving towards
.I v1file,
simulating an aperture of diameter
.I aperture
in world coordinate units.
When rendered and averaged together, these views will result in
a picture with motion and depth-of-field
blur due to a camera changing from v0 to v1
in a relative time unit of 1, whose shutter is open starting at v0 for
.I speed
of these time units.
Either
.I pinterp(1)
or
.I rpict(1)
may be called to do the actual work.
(The given
.I v0file
must also be passed on the command line to the chosen renderer, since
.I pmdblur
provides supplemental view specifications only.)\0
.PP
For
.I pinterp,
feed the output of
.I pmdblur
to the standard input of
.I pinterp
and apply the
.I \-B
option to blur views together.
In most cases, two pictures with z-buffers at v0 and v1 will
get a satisfactory result, though the perfectionist may wish to
apply the
.I \-ff
option together with the
.I \-fr
option of
.I pinterp.
.PP
To use
.I pmdblur
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 pmdblur.
We have found a
.I nsamp
setting somewhere between 7 and 15 to be adequate for most images.
Relatively larger values are appropriate for faster camera motion.
.PP
The
.I \-pm
and/or
.I \-pd
options of
.I rpict
may be used instead or in combination to blur animated frames, with
the added advantage of blurring reflections and refractions according
to their proper motion.
However, this option will result in more noise and expense than using
.I pmdblur
with
.I pinterp
as a post-process.
If both blurring methods are used, a smaller value should be given to the
.I rpict
.I \-pm
option equal to the shutter speed divided by the number of samples, and the
.I \-pd
option equal to the aperture divided by the number of samples.
This will be just enough to blur the boundaries of the ghosts
which may appear using
.I pmdblur
with a small number of time samples.
.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 motion blur between two frames of a walk-through
animation, where the camera shutter is open for 1/4 of the
interframe distance with an aperture of 0.1 world units:
.IP "" .2i
pmdblur .25 .1 8 fr1023.hdr fr1024.hdr | pinterp \-B \-vf fr1023.hdr \-x 640 \-y 480
fr1023.hdr fr1023.zbf fr1024.hdr fr1024.zbf > fr1023b.hdr
.SH AUTHOR
Greg Ward
.SH "SEE ALSO"
pcomb(1), pdfblur(1), pinterp(1), pmblur(1), rcalc(1), rpict(1), vwright(1)