public Vector3f gravity(Vector3f storeResult) {
        Vector3f result = (storeResult == null) ? new Vector3f() : storeResult;
        result.set(gravityVector);
        return result;
    }
Copy this control's gravitational acceleration for Ragdoll mode.

@param storeResult storage for the result (modified if not null)
@return an acceleration vector (in physics-space coordinates, either
storeResult or a new vector, not null)
jme3-jbullet/src/main/java/com/jme3/bullet/animation/DacConfiguration.java