I instantiate a nurbs surface with `ON_NurbsSurface(3, false, 5, 5, 37, 37);`

Then I call `MakePeriodicUniformKnotVector();`

When I print the knot vector I get numbers going from 0 to 33 and 6 zeros at the end. This makes 40 values which is 37 + 5 - 2 so it is ok. I would have expected to get values from -3 to 36, because I could find such values on other examples.

Do I have a regular behavior? What means the 6 zeros at the end?

Because of those zeros, all my calculations are going wrong.