public Vector4f subtractLocal(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>subtractLocal</code> subtracts 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 subtract
@return this
jme3-core/src/main/java/com/jme3/math/Vector4f.java