[ODE] Two questions:

Jon Watte (ODE) hplus-ode at mindcontrol.org
Mon May 21 10:23:17 MST 2007

ODE is a Baraff-like constraint solver, that uses semi-implicit Euler 
(first order) integration. This is chosen because it's a good trade-off 
between speed and stability for games.

People choose a time step that gives them the result they want. 
Sometimes, they choose 16.67 ms, to tie to the 60 Hz update rate of an 
assumed display device. Sometimes, they choose 10 milliseconds, just 
because it seems to work pretty well, and then display in an 
interpolated fashion at whatever frame rate you happen to update at. 
Sometimes, the time step is chosen based on the fastest object in the 

However, you should not vary the time step once chosen, because doing so 
will introduce instability (because of the first order integrator).


          / h+

Andrew Riehm wrote:
> 1) What methods are implemented in ODE for solving ordinary differential 
> equations?  Why were those methods chosen?  Have other methods been 
> considered?
> 2) How do people writing simulations using ODE determine the size of a 
> given time step?
> --
> Andrew Riehm
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> ODE at ode.org
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