public void setGravity(Vector3f gravity) {
        rBody.setGravity(Converter.convert(gravity, tempVec));
    }
Set the local gravity of this PhysicsRigidBody<br>
Set this after adding the node to the PhysicsSpace,
the PhysicsSpace assigns its current gravity to the physics node when it's added.
@param gravity the gravity vector to set
jme3-jbullet/src/main/java/com/jme3/bullet/objects/PhysicsRigidBody.java