public Quaternion inverseLocal() {
        float norm = norm();
        if (norm > 0.0) {
            float invNorm = 1.0f / norm;
            x *= -invNorm;
            y *= -invNorm;
            z *= -invNorm;
            w *= invNorm;
        }
        return this;
    }
Inverts the quaternion and returns the (modified) current instance. For
a quaternion with norm=0, the current instance is unchanged.

@return the current instance (for chaining)
jme3-core/src/main/java/com/jme3/math/Quaternion.java