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Creating a B-spline with a single control point

Question asked by J. R. on Apr 1, 2019
Latest reply on Apr 7, 2019 by J. R.

I am trying to recreate a certain shape in Solidworks that was originally modeled in software called Delftship, in order to parametrize and modify it. In Delftship, this shape was created using B-splines with a single control point, which can be seen in this screenshot (the red lines are lines connecting base/control points, and the curves are thin black lines):

 

01.png

 

Now, I imported this body into Solidworks, so I can use it as a visual reference to determine what kind of spline I have to use here to have the same curvature with a single control point (this is very important). Herein lies the problem. As I understand it, Solidworks supports B-splines (regular splines) and Bezier (style splines). Unfortunately, I can't seem to produce a curve that would have the same curvature as in the picture above, having a control point in the exact same spot. Here's my attempt to recreate one of the curves on the imported model. With a regular spline (which is B-spline, as I understand), which has a control point inside the spline, I get this:

 

03.png

 

As you can see, not even close. Doesn't matter where I put that control point, the curvature is just not the same. It is possible to approximate the original curvature with tangency controls on that spline, but that is a lot of manual tinkering, and what I need is a spline that naturally falls into this shape... Like in my first screenshot.

 

Style spline does have a control point like that one I need, but since it's a Bezier curve, I get this result:

 

02.png

 

Which, again, is not what I need, but that's to be expected from a Bezier. It seems that there is a way to make a B-spline with control points outside the curve with a style spline, but unfortunately, it requires a minimum of 2 control points:

 

04.png

 

As you can see, the curvature is now approximately the same as in the original shape, but the placement of these control points doesn't make a sense compared to the single control point in the Delftship (which, as I said, also uses B-splines).

 

Can someone shed any light on this issue, please? Am I misunderstanding something essential about these curves? How can I reproduce that B-spline using a single control point in Solidworks?

 

P.S. I know I can Convert Entities to get these curves from the imported model... But as I said that's not the point, because I want to learn to recreate these curves in order to have a parametric shape.

 

Thank you in advance

 

EDIT: I am attaching the imported model in case you want to try this for yourself.

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