.\" 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)