public Vector3f add(Vector3f vec) {
        if (null == vec) {
            logger.warning("Provided vector is null, null returned.");
            return null;
        }
        return new Vector3f(x + vec.x, y + vec.y, z + vec.z);
    }
Adds the argument and returns the sum as a new instance. If the argument
is null, null is returned. Either way, the current instance is
unaffected.

@param vec the vector to add (unaffected) or null for none
@return a new Vector3f or null
jme3-core/src/main/java/com/jme3/math/Vector3f.java