[ODE] Possible solution to unstable rotating bodies problem

Jon Watte hplus-ode at mindcontrol.org
Wed Apr 6 17:16:30 MST 2005

> Seriously, these sort of arguments really have no truck with me (i.e. "It
> would make things correct in the sense of the program not crashing, but
> you'd need an extra bit and an if-then-else for every object which would
> slow things down by 0.0001%, so let's just ignore it.").

There are tons of simulations that don't explode. With sufficient damping, 
any simulation can be made to not explode. Tyler reports that extreme 
amounts of damping still didn't work for him -- I would attribute that to 
a bug, rather than to damping not being enough to work around the 
numerical problems inherent in this kind of simulation. Thus, you're 
trading a solution that costs cycles and memory, against a solution that 
is currently implemented and uses much less cycles and memory. The only 
reason to choose the new option over the old would be that you don't like 
the characteristics of a sufficiently dampened simulation, and what I'm 
saying is that I'm not sure whether your preference, or the needs of 
people who use ODE in memory- and cycle-constrained environments, is the 
bigger need.


			/ h+

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