uwestoehr wrote: ↑Mon Jan 10, 2022 5:38 pm
Most of my real-life sketches contains B-Splines (I even wrote this Wiki page:
https://wiki.freecadweb.org/B-Splines ). B-Splines are a basic feature of CAD in my opinion.
Therefore I need to understand the issue properly.
But Bsplines are not scalable, as they a are defined by a math formula that may use "control points" "poles?", "knots?", that are difficult to "transpose".
EDIT:
Interesting reading could be:
https://www.cl.cam.ac.uk/teaching/2000/ ... node4.html
At least for the concluding consideration:
If there are no pressing reasons for doing otherwise, your B-spline should be defined as follows:
k=4 (cubic);
no multiple control points;
uniform (for a closed curve) or open uniform (for an open curve) knot vector.
END EDIT
EDIT2
Some more research, if I have guessed weel you could transform you bspline, apllying the tansformation to the control points.
According to this text.
http://home.iitk.ac.in/~jrkumar/downloa ... %20New.pdf
The entire B-spline curve can be affinely transformed by transforming the control points and redrawing the curve from the transformed points.
END EDIT2
EDIT3
I'have noted the absence of @Chris_G in this disccussion.
Chris_G wrote: ↑Mon Dec 27, 2021 3:35 pm
Sorry for poking
Maybe he could help.
END EDIT3
I have had some problems with B-Splines, and usually you could use this approach:
- discretize the B-Spline segment
- transform the points to the new shape
- use the "transformed points" to obtain a new B-Spline in the final objects
Usually as you are making a transformation, you have to create a new in this case a new face.
In case of taper you could also join two corresponding b-splines if they have "same number of edges" with a ruled surface, but this is only a guess as I have not used it in real code, usually I approximate them to BiArcs and operate on them.
Hoping having guessed the problem right.
Regards
Carlo D.