I'm using the java port of Bullet Physics (jBullet) for a game I'm making.

I'm trying to move a bunch of bodies by simply calling body.setCenterOfMassTransform with a transform that has been translated (no rotation here) by the same amount for all bodies.

Problems occur whenever I try to do this for bodies that already had contact points (bodies bounce from each other).

I tried to fix that with this nifty bit of code, to no avail (I thought perhaps the contact point cache needed to be translated as well):

Code: Select all

```
public void translateManifolds(CollisionObject colObj, Vector3f dx) {
Dispatcher dispatcher = getDispatcher();
// Find all manifold caches associated with this collision object
int numManifolds = dispatcher.getNumManifolds();
for (int i = 0 ; i < numManifolds ; i++) {
PersistentManifold manifold = dispatcher.getManifoldByIndexInternal(i);
if (manifold.getBody0() == colObj || manifold.getBody1() == colObj) {
int numContacts = manifold.getNumContacts();
for (int j = 0 ; j < numContacts ; j++) {
ManifoldPoint point = manifold.getContactPoint(j);
// Translate all contact points by dx
point.positionWorldOnB.add(dx);
point.positionWorldOnA.add(dx);
}
}
}
}
```

I'm aware I should probably use a linear velocity for all bodies involved and let the engine solve the displacement for me, but if I could avoid that, I would prefer doing it akin to the way presented above. One of the bodies is actually a Kinematic body (zero mass) that I don't want be subject to change in velocity from collisions from the other bodies, and the engine won't actually move a body even if specified a linear velocity unless that body has an actual mass.

Thank you for any tip,

Guillaume