Real-Time Physics Simulation Forum

Posted: **Tue Dec 14, 2010 11:09 am**

Hello!

I am scaling a child shape of a compound object. The scaling seems fine in debug draw but the collisions does not take place. The body should be pushed out from a nearby wall when the child gets enlarged, this does not happen. I have tried scaling the shape without a compound object and that works fine, the body gets pushed out. Here's my code for scaling the object:

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    if (mBody->getCollisionShape()->isCompound()){
      btCompoundShape * comp = (btCompoundShape *)mBody->getCollisionShape();
      btCollisionShape * child = comp->getChildShape(0);
      if(child!=0){
        child->setLocalScaling(btVector3(2.5,2.5,1));
      }
      ((btCompoundShape *)mBody->getCollisionShape())->recalculateLocalAabb();
    }

I have also tried updating the inertia tensor and setMassProps without any success. Any help appreciated!

Posted: **Tue Dec 14, 2010 4:47 pm**

To fix the collision issues, try calling the

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void	btCompoundShape::updateChildTransform(int childIndex, const btTransform& newChildTransform)

using the old transform. This should update the internal data structures.

For the inertia tensor, make sure to remove the object from the world before making the change, and re-insert it afterwards.
Thanks,
Erwin

Posted: **Wed Dec 15, 2010 9:01 am**

Thanks, that solved it =)

Is it necessary to update the inertia tensor if I have disabled angular factor with setAngularFactor(0)?

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