[ODE] Contacts not constraining user forces ?

Erin Catto erincatto at sbcglobal.net
Wed Apr 20 23:13:34 MST 2005

A few things to try:

1. Set the contact CFM and global CFM to zero.
2. Depending on your masses, that force may be very large compared to
gravity. Try reducing the force by factors of 10.
3. Is a contact point still being generated in the second version? If so, is
the normal and penetration the same?
4. Try the same setup with a plane or box instead of the mesh.


-----Original Message-----
From: ode-bounces at q12.org [mailto:ode-bounces at q12.org] On Behalf Of Marco
Sent: Wednesday, April 20, 2005 6:22 PM
To: ode at q12.org
Subject: [ODE] Contacts not constraining user forces ?


I ran into a strange problem in a simple test case: a sphere dropped onto a 
static Trimesh with any world gravity enabled comes to a rest on top of the 
trimesh. If however I adda tiny amount of force using dBodyAddForce before 
stepping then the sphere sinks into that mesh.
Any suggestions on what might be going wrong ?

// this works fine:
while (1) {
  // add contacts here
  dWorldStep( pWorld, 0.05f );
// this makes the sphere sink
while (1) {
  dBodyAddForce( pSphereBody, 0,0,-1);
  // add contacts here
  dWorldStep( pWorld, 0.05f );

- Marco 

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