Re: [CsMain] ode help

[Daniel D. <du...@ya...>]

On Fri, 13 Dec 2002, Mark Rawls wrote:

-->When I have tried to add torque to an object (to rotate it), it kept
-->spinning (as I would expect given what I understand of physics).  However,
-->I couldn't get it to stop, no matter what.  I tried to set torque to the
-->opposite of current torque, used differing combinations of AddTorque and
-->AddRelTorque, but it didn't *stop completely.* At times it would move very
-->slowly and I got the impression that it was just an unavoidable floating
-->point and/or integrator inaccuracy problem.  Is this right?  How do I "fix"
-->it?  Or is it okay to call SetOrientation just once, as in initilization;
-->or does this effect stability for the entire duration?

That's one of those cases its probably easier to set the velocity.  
SetAngularVelocity (csVector3 (0,0,0);  ODE has extra functionality to 
correct for errors in order to maintain stability.  It makes some assumptions 
about the motion of the object.  So its probable that even though you exactly 
counteract the force on the object, the error-smoothing term will actually 
over or under correct you away from zero.

It would be better from an engine standpoint however to add some viscosity 
factor, since ODE doesn't solve rotational friction.  Keep in mind though that 
normally with joints and non-round bodies it would come to rest at some point 
after collisions and the like.

I'll put it on my list to add dampeners of some kind to the body interface.

-->Also, I just noticed the AddForceAtPos.  Is this another way to go about
-->having torque applied to a body?  Does it suffer from the same problem I
-->think AddTorque has?

Yes it does.  AddForceAtPos will probably act like AddTorque unless you add
exactly at the center of gravity for the object.

-- 
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