public Quaternion toRotationQuat(Quaternion q) {
        return q.fromRotationMatrix(m00, m01, m02, m10,
                m11, m12, m20, m21, m22);
    }
Returns the rotation component of the coordinate transform.

<p>Assumes (but does not verify) that the transform consists entirely of
translation, rotation, and positive scaling -- no reflection or shear.

@param q storage for the result (not null, modified)
@return the rotation component (in {@code q}) for chaining
jme3-core/src/main/java/com/jme3/math/Matrix4f.java