public static void Subtract(ref Matrix3x3 a, ref Matrix3x3 b, out Matrix3x3 result)
{
float m11 = a.M11 - b.M11;
float m12 = a.M12 - b.M12;
float m13 = a.M13 - b.M13;
float m21 = a.M21 - b.M21;
float m22 = a.M22 - b.M22;
float m23 = a.M23 - b.M23;
float m31 = a.M31 - b.M31;
float m32 = a.M32 - b.M32;
float m33 = a.M33 - b.M33;
result.M11 = m11;
result.M12 = m12;
result.M13 = m13;
result.M21 = m21;
result.M22 = m22;
result.M23 = m23;
result.M31 = m31;
result.M32 = m32;
result.M33 = m33;
}