B-Spline improvements

[microelly2]

short question:
what are the benefit of this method over a pice-wise bspline of degree3 which is already doable with the gui?

If i have complex objects it is easier to have only one curve than many pices.
inserting a knot allows to define new segments where local deformations can start.

bp_794.png (68.86 KiB) Viewed 617 times

In the example the middle curves of the blue and red strips are sketcher splines.
there is a syncronization between the red and the blue sketches in background
to edit the surface I can decide which sketch I want to modify.
For a refinement I add a strip and than I edit the sketch.
the borders of the strips hold the local tangent conditions. My idea for them is to bend and stretch them by a graphical "joystick" feature

[hammax]

… one year later:
When I see, what you can do with sketcher constraints
https://forum.freecadweb.org/viewtopic.php?f=8&t=37197
my hope is, that there is a way to make visible points, especially the knot points in BSpline outside SketcherWB.
(what's possible with seedpoint, could also be possible with other regular points ???)
I am working very often with sketcher bsplines and sometimes it could be useful to snap some knot points
or have them as "seed-line" e.g. in a loft.
Until now knot points are barely useless, as long as I don't apply the special tools to change multiplicity a.s.o.

[abdullah]

… one year later:
When I see, what you can do with sketcher constraints
https://forum.freecadweb.org/viewtopic.php?f=8&t=37197
my hope is, that there is a way to make visible points, especially the knot points in BSpline outside SketcherWB.
(what's possible with seedpoint, could also be possible with other regular points ???)
I am working very often with sketcher bsplines and sometimes it could be useful to snap some knot points
or have them as "seed-line" e.g. in a loft.
Until now knot points are barely useless, as long as I don't apply the special tools to change multiplicity a.s.o.

The main limitation to that is that the sketcher points are limited to be non-defining (construction if you wish) in the current implementation. It is not straightforward to change this behaviour.

However, what you want can be done with Python (ask MicroElly ), or with his arrangement.

Make a carbon copy of your sketch with the B-Spline in a new sketch, so that the B-Spline is construction. Now make a normal line segment with at least one endpoint coincident with con knot (yes, there is a very special arrangement by which you can make a coincidence constraint on a knot). Now, if you move the construction b-spline, the knot follows. You can now exit edit mode and use the endpoint of the normal line segment you just entered.