Problem with joining Bezier curves in blender 3.5.1

Question

This is my first post here so I apologize in advance for any mistakes I make.

I am trying to join two bezier curves using the add-on "Curve Tools". The steps I follow are simple

1. Add a Bezier curve, edit and shape it as desired (including extrude).
2. Add another curve, edit and shape it as desired.
3. Join both curves (Ctrl+J).
4. Back into edit I align two vertices together and I use Sanitize > Join Splines in the N-Panel.

I always succeed in joining the first two vertices but I can't join any other vertices.

I have repeated this multiple times and always with the same results. I also noticed that the handles of the vertices change once I apply the "Join Splines".

Example file:

Any idea how can I merge more than two vertices in a design? Is there something wrong with my setup or my approach. Your feedback is welcomed

I am using Blender 3.5.1 on macos 13.4, M1 Chip.

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thanks a lot @Gordon Brinkmann. You have addressed the main points I was struggling with. The shape I am trying to create is a branch for a tree. My goal was to create a bezier curve that makes up the branch and then add thickness by using a bevel. I can get the effect but the branches are going to be disjoint and can be affected by any edits. I was looking for a way to make them all as one object (welded or something similar). thanks for the help and any advice is highly appreciated

Answer 1

Would you mind adding a sketch in which way you want to merge control points (vertices are parts of a mesh object)?

In general: A curve holds one or more splines, a spline consists of two endpoints, - one at the start and another at the end - and can have control points inbetween.

You can connect two endpoints of separate splines to join them to a larger spline.

You cannot connect the start and end point of a single spline manually, to do this you must enable the Cyclic option in the Active Spline settings of the curve's properties. Note: this can be set individually in Edit Mode for each spline within a curve object.

You also cannot connect control points somewhere on a spline with others on the same or a different spline. A spline cannot branch into multiple splines.

Here is an overview and some examples with a curve object that has two splines:

The red points above cannot be connected with other points in any way, so connections like the following are not possible:

The green endpoints can be connected, however to close the splines you cannot do it manually - there will alyway be a gap between first and last point unless you set the spline(s) to Cyclic. In this case the spline(s) will be closed automatically:

Nevertheless you can manually connect an endpoint to the endpoint of another spline if they are both open, for example the green connection in the example below. If you want to close the spline you again need to set the spline to Cyclic and the blue connection will automatically be closed: