Re: AN interesting comment.

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Nathaniel Bletter (nat++at++od.sri.com)
Thu, 16 Jan 1997 15:53:06 -0800

In studies we've done with simple images, double or triple framing causes
multiple images of the moving object to appear as your eye is moving at a
constant rate but the object is flashing twice in one spot, then twice in the
next spot. You will get (refresh rate)/(update rate) images of the object, so
for a 15 Hz update on a 60 Hz screen, you'll get 4 images. These images can be
very close together and low contrast so they're not always visible, but it is a
real effect we have observed.

On Jan 16, 4:51pm, Mike Weiblen wrote:
> Subject: Re: AN interesting comment.
> The double framing would seem to invite temporal aliasing,
> which is perhaps perceived as a motion blur??
>
> -- mew
>
>
> Steve Baker wrote:
> >
> > I found this interesting comment in a document in Jim Blinn's home page
> > out there on the web:-
> >
> > > A common cheat in animation is to do double framing, that
> > > is, to only render every other frame and to record each rendered frame
> > > twice. We all expect that single framing is preferable to double framing,
> > > its only disadvantage is that single framing takes longer to render.
> > > There is another effect of double framing however. A motion that is
> > > double framed seems to move faster than one that is single framed,
> > > even if they take an identical amount of wall-clock time to take place.
> > > Double framing is therefore sometimes used by conventional animators
> > > to add liveliness to scene.
> >
> > This seems very suprising - if it's true then it would appear to have
> > rather severe implications for simulations running at 30Hz. If time
> > somehow seems distorted in this way then vehicle operators (pilots
> > especially) might get false speed cues with 30Hz simulations!
> >
> > Has anyone else out there heard this? Are there studies to show any
> > kind of effect like that?
> >
> > Mr Blinn is presumably too busy to answer his email - I didn't get a
> > reply when I asked him for backup info.
> >
> > Steve Baker 817-619-1361 (Vox-Lab)
> > Hughes Training Inc. 817-619-8776 (Vox-Office/Vox-Mail)
> > 2200 Arlington Downs Road 817-619-4028 (Fax)
> > Arlington, Texas. TX 76005-6171 Steve++at++MrEd.bgm.link.com (eMail)
> > http://www.hti.com (external) http://MrEd.bgm.link.com/staff/steve
(intranet)
> > http://web2.airmail.net/sjbaker1
    (external)
> >
> > "You can't destroy the Earth - that's where I keep all my stuff!" - The
Tick.
>
> --
> Mike Weiblen talkto:972-960-2301 x292
> PARADIGM Simulation, Inc. faxto:972-960-2303
> 14900 Landmark, Suite 400 mailto:mew++at++paradigmsim.com
> Dallas TX 75240 http://www.paradigmsim.com
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>-- End of excerpt from Mike Weiblen

--


Nat Bletter
SRI International
nat++at++od.sri.com
http://os.sri.com/people/nat/
(415) 859-4358
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