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[pwc] Head tracking DOF (was Re: Latency)

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Subject: [pwc] Head tracking DOF (was Re: Latency)
From: Tommi Ilmonen <>
Date: Wed, 20 Jun 2007 22:50:21 +0300
Hi.

David Wennström <>:

> > Yes, it is a long time. BTW: If you do head tracking you can often get
> > away with 5DOF tracking, since you are probably only interested in the
> > two eyes.
>
> Which DOF can I skip? The "roll" angle?

I am not sure which is the "roll" angle, but if we assume that your eyes lie on
the X axis (head coordinate system), then you can just forget rotation about
the X axis. Now your markers might be slightly off the X-axis and theoretically
ignoring that rotation causes an error unless also the markers are on the
X-axis. How-ever, most tracking systems are so inaccurate anyhow that nobody
really cares about this ;-)

We used to just assume that eyes are a bit beneath the markers (which were
attached above the stereo glasses) and things went fine. Not hifi, but good
enough for the purpose.

> > > I am also very interested in links and projects that I can read about 3D
> > > tracking system like this in general and particularly head tracking.
> > >
> > Here is link to one (that I wrote). I think most would be hidden in all
> > kinds of SW systems.
> >
> >
>
http://csdl2.computer.org/persagen/DLAbsToc.jsp?resourcePath=/dl/proceedings/&toc=comp/proceedings/vr/2006/0224/00/0224toc.xml&DOI=10.1109/VR.2006.139
> >
>
> Thank you, I'll look into it.

I can dig up the pdf if you cannot get from that site.

> > We used Apple iSight cameras which were certainly cheap enough (but you
> > cannot lock the white balance...)
> >
> > The unibrain board cameras would be very cheap, but then you are down to
> > 30 fps again...
> >
>
> It's not so much the fps but the latency from picture taken to getting it to
> the PC. Currently I will be stuck with the SPC900NC camera - trying to get it
> a little bit faster... :)

Yes. There is data transmission latency and then many (most?) consumer cameras
do frame integration to reduce noise (and increase effective latency), which of
course is the last thing you want...


--
Tommi

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