[ODE] box stacking instability

[Peter Amstutz]

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I've noticed that the "boxstack" test is unstable as well, although not to
the degree that the test program I'm using does.  If one box comes to rest
on another, while it doesn't pop up (as in this other demo) it does appear
to vibrate and will move about -- I presume this is due to impulses
correcting for penetration of the top box into the lower box.

I'm talked to a professor who knows something about dynamics systems, and
his understanding is that the impulse-based method in inherently unstable
in this configuration -- using this algorithm it is almost impossible for
the system to come to equilibrium.  This seems to be an enormous problem,
and one which makes ODE rather useless for my purposes.  It looks like I
shall have to just use collision detection with some basic physics hacked
on...  I need for it to be possible for objects to be supported by others,
such as platforms on which other objects rest.  It seems that ODE handles
the case of stability on a plane quite well, but that is rather limited
use compared to the general case :-(

On a side note, the same professor mentioned the Arachi dynamics engine
(www.arachi.com).  It's commercial and exceedingly expensive ($30,000) but
he speaks very highly of it.  It would be interesting to potentially adopt
some of their techniques...

[   Peter Amstutz   ][ amstutz@cs.umass.edu ][ tetron@interreality.org  ]
[Lead Programmer][Interreality Project][Virtual Reality for the Internet]
[ VOS: Next Generation Internet Communication][ http://interreality.org ]
[ http://interreality.org/~tetron ][ pgpkey:  pgpkeys.mit.edu  18C21DF7 ]
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