Extra control points when extracting boundary

Hi,

Why do I get extra control points when I extract the boundary of a surface? I switched on the control points of the surface in my screenshot and, as you can see, i only have them in the corners. The surface is planar, all edges are merged…

It is the same as in rhino.
In rhino, try to join a line (degree 1) and an arc (degree 2) together and then turn on control point: the line will have an “additional” control point in the mid.
When joining many curves the resulting polycurve will have the degree of the hightest degree of its segments, after then in the polycurve every segment will have at least a number of control points equal to the degree +1 (counting also endpoints).
2019-06-06%2018_14_36-Window

Explode your curve before using “Control Points” component, you’ll have what you want.

Also, if you are getting more point than what you expected it means that some of the segments is not a straight line, a curve have a degree = 3 . Check your geometries.

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Ok ,I understand. thanks!
I was curious.