[ODE] Collision Detection ... again

[Jon Watte]

As the FAQ says, or shoudl say, two things will help with this:

1) Add damping. For each object, for each step, add counter-
   force scaled by linear velocity, and counter-torque scaled 
   by angular velocity. From memory, it looks something like:

   /*  Apply damping to the body to get it to settle properly     */
   /*  over time. This also simulates "air drag" or "rolling      */
   /*  friction" to some extent.                                  */
   /*  Change "-0.01f" to some other negative number for tuning.  */
   dVector3 v;
   dBodyGetLinearVelocity( body, v );
   v[0] *= -0.01f;   v[1] *= -0.01f;   v[2] *= -0.01f;
   dBodyAddForcce( body, v );
   dBodyGetAngularVelocity( body, v );
   v[0] *= -0.01f;   v[1] *= -0.01f;   v[2] *= -0.01f;
   dBodyAddTorque( body, v );

2) Use auto-disable, or implement auto-disable yourself. When 
   a body has been more or less at rest for some number of steps, 
   freeze it in its current location. This increases stability, 
   in addition to reducing computational load.


Actually, I can't find that code snippet (or anything like it) 
in the FAQ or documentation sections dealing with this settling 
problem; could anyone add it perhaps?


Cheers,

			/ h+


-----Original Message-----
From: ode-bounces at q12.org [mailto:ode-bounces at q12.org]On Behalf Of
Andrew Cross
Sent: Monday, June 21, 2004 3:10 AM
To: ode at q12.org
Subject: [ODE] Collision Detection ... again


All,

I know that the whole subject of collision detection has probably been
discussed to death at this point, however I am seeing a relatively annoying
problem when {planes or boxes} are collided with {cylinders or boxes}. If
you just drop (say) a cylinder onto a plane it will bounce correctly,
however once it has bounced around a bit and settled down, it starts to
"swim" meaning that the two surfaces can penetrate and seem to move around
certain axis's. This is somewhat hard to describe, but I have uploaded a
short movie that shows this problem on :
http://www.3dgraphics.com/~deadline/CollisionProblem.wmv
This shows the collision of a capped cylinder with a plane.

Thanks in advance for your help.

Andrew

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