public Vector4f addLocal(Vector4f vec) {
        if (null == vec) {
            logger.warning("Provided vector is null, null returned.");
            return null;
        }
        x += vec.x;
        y += vec.y;
        z += vec.z;
        w += vec.w;
        return this;
    }
<code>addLocal</code> adds a provided vector to this vector internally,
and returns a handle to this vector for easy chaining of calls. If the
provided vector is null, null is returned.

@param vec
           the vector to add to this vector.
@return this
jme3-core/src/main/java/com/jme3/math/Vector4f.java