public float3 Col(int i)
{
switch (i)
{
case 0:
return new float3(M11, M21, M31);
case 1:
return new float3(M12, M22, M32);
case 2:
return new float3(M13, M23, M33);
default:
return new float3(0, 0, 0);
}
}