public void toRotationMatrix(Matrix3f mat) {
        mat.m00 = m00;
        mat.m01 = m01;
        mat.m02 = m02;
        mat.m10 = m10;
        mat.m11 = m11;
        mat.m12 = m12;
        mat.m20 = m20;
        mat.m21 = m21;
        mat.m22 = m22;
    }
Determines the rotation component of the coordinate transform.

<p>If the transform includes scaling or reflection or shear, the result
might not be a valid rotation matrix.

@param mat storage for the result (not null, modified)
jme3-core/src/main/java/com/jme3/math/Matrix4f.java