[ODE] Re: dBodyAddForce / dBodyAddTorque don't do anything!

[Matthew D. Hancher]

> I've now found that I can get something to happen, but I have to use
> absolutely enormous forces.  For instance if I call with fx, fy or fz
> around 10000000 or even larger, then the ball does move.  Is this
> normal?

Are you calling dBodyAddForce() once, or every frame?  The force is
reset to zero at the end of each step.  Calling dBodyAddForce()
once applies the force only for the very first time step, i.e. it
simulates an impulse, and in that case you do need very large force
values to see anything; the dWorldImpulseToForce() function is
designed to scale them up appropriately.  If you want to simulate a
continuous force then you must call dBodyAddForce() at every step.
(It is designed this way because external forces typically vary
from step to step.)

Matt

Matthew D. Hancher
Intelligent Systems Division
NASA Ames Research Center
mdh at email.arc.nasa.gov