public virtual void Enable(bool bImmovable, float mass)
{
//set whether the object can move
Body.Immovable = bImmovable;
//calculate the centre of mass
Vector3 centerOfMass = SetMass(mass);
//adjust skin so that it corresponds to the 3D mesh as drawn on screen
Body.MoveTo(Transform3D.Translation, Matrix.Identity);
//set the centre of mass
Collision.ApplyLocalTransform(new Transform(-centerOfMass, Matrix.Identity));
//enable so that any applied forces (e.g. gravity) will affect the object
Body.EnableBody();
}