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.\" RCSid "$Id: pmdblur.1,v 1.1 2005/01/18 03:59:40 greg Exp $"
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.TH PMDBLUR 1 1/17/05 NAME
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pmdblur - generate views for combined camera motion and depth blurring
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.SH SYNOPSIS
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.B pmdblur
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.B speed
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.B aperture
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.B nsamp
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.B v0file
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.B v1file
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.SH DESCRIPTION
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.I Pmdblur
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takes two viewfiles and generates
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.I nsamp
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views starting from
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.I v0file
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and moving towards
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.I v1file,
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simulating an aperture of diameter
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.I aperture
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in world coordinate units.
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When rendered and averaged together, these views will result in
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a picture with motion and depth-of-field
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blur due to a camera changing from v0 to v1
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in a relative time unit of 1, whose shutter is open starting at v0 for
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.I speed
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of these time units.
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Either
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.I pinterp(1)
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or
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.I rpict(1)
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may be called to do the actual work.
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(The given
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.I v0file
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must also be passed on the command line to the chosen renderer, since
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.I pmdblur
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provides supplemental view specifications only.)\0
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.PP
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For
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.I pinterp,
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feed the output of
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.I pmdblur
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to the standard input of
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.I pinterp
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and apply the
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.I \-B
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option to blur views together.
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In most cases, two pictures with z-buffers at v0 and v1 will
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get a satisfactory result, though the perfectionist may wish to
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apply the
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.I \-ff
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option together with the
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.I \-fr
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option of
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.I pinterp.
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.PP
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To use
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.I pmdblur
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with
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.I rpict,
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apply the
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.I \-S
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option to indicate a rendering sequence, and set the
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.I \-o
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option with a formatted file name to save multiple output
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pictures.
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When all the renderings are finished, combine them with the
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.I pcomb(1)
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program, using appropriate scalefactors to achieve an average.
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Note that using
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.I rpict
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is MUCH more expensive than using
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.I pinterp,
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and it is only recommended if the scene and application
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absolutely demand it (e.g. there is prominent refraction that
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must be modeled accurately).
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.PP
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For both
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.I pinterp
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and
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.I rpict,
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the computation time will be proportional to the number of views from
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.I pmdblur.
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We have found a
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.I nsamp
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setting somewhere between 7 and 15 to be adequate for most images.
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Relatively larger values are appropriate for faster camera motion.
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.PP
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The
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.I \-pm
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and/or
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.I \-pd
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options of
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.I rpict
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may be used instead or in combination to blur animated frames, with
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the added advantage of blurring reflections and refractions according
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to their proper motion.
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However, this option will result in more noise and expense than using
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.I pmdblur
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with
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.I pinterp
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as a post-process.
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If both blurring methods are used, a smaller value should be given to the
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.I rpict
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.I \-pm
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option equal to the shutter speed divided by the number of samples, and the
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.I \-pd
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option equal to the aperture divided by the number of samples.
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This will be just enough to blur the boundaries of the ghosts
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which may appear using
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.I pmdblur
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with a small number of time samples.
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.PP
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To simulate a particular camera's aperture, divide the focal length of
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the lens by the f-number, then convert to the corresponding
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world coordinate units.
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For example, if you wish to simulate a 50mm lens at f/2.0 in
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a scene modeled in meters, then you divide 50mm by 2.0 to get 25mm,
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which corresponds to an effective aperture of 0.025 meters.
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.SH EXAMPLES
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To use
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.I pinterp
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to simulate motion blur between two frames of a walk-through
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animation, where the camera shutter is open for 1/4 of the
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interframe distance with an aperture of 0.1 world units:
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.IP "" .2i
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pmdblur .25 .1 8 fr1023.pic fr1024.pic | pinterp -B -vf fr1023.pic -x 640 -y 480
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fr1023.pic fr1023.zbf fr1024.pic fr1024.zbf > fr1023b.pic
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.SH AUTHOR
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Greg Ward
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.SH "SEE ALSO"
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pcomb(1), pdfblur(1), pinterp(1), pmblur(1), rcalc(1), rpict(1), vwright(1)
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