Add node to spline - why do we need select existing node first?

[vanowm]

I'm a bit baffled with splinedit -> fit data -> add.

why do we need select first an existing node on a spline in order to add a new node? why can't we just add a node?

[lrm]

If the spline was created using the Fit point method it will have a series of fit points that the spline passes through in the order the poins were specified.  If you want to add a new fit point you have to indicate an existing fit point so that it is clear where in the order the new one should be.  For example, if there are 7 fit points and you want to add one between #3 and #4, then pick #3 after specifying Add. 

[vanowm]

Wouldn't it be the same as simply counting points from the start? So, if you simply clicked between #3 and #4 wouldn't it be obvious that it's between #3 and #4 and not somewhere else?

[lrm]

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 ...if you simply clicked between #3 and #4 wouldn't it be obvious that it's between #3 and #4 and not somewhere else?

 

It may not be so obvious where the new point should be located with respect to the other points.  For example, should the "new point" in this example be before or after point 3 or perhaps somewhere else n the sequence?

 

 

 

Edited March 30 by lrm

[vanowm]

Oh, I see. It allows clicking anywhere, not necessarily on spline itself...

In my experience, I always used NEA when adding nodes, to make sure they land exactly where I wanted them to, so that extra step is annoyingly unnecessary...

 

Thank you.

 

P.S.

Before I waste my time creating it, is there already a script that would allow simply select a spline and add/remove nodes anywhere on it with a single click?

Edited March 30 by vanowm

[lrm]

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In my experience, I always used NEA when adding nodes, to make sure they land exactly where I wanted them to, so that extra step is annoyingly unnecessary...

If you are using NEA then you are adding a fit point on the spline at a point where it is already passing through!  What is the reason for adding the additional point?  It won't modify the spline unless you, of course, move it.  In general, it is beter to have as few fit points, or control vertices, as possible. More points increase the likelyhood of getting undersirable undulations.

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Before I waste my time creating it, is there already a script that would allow simply select a spline and add/remove nodes anywhere on it with a single click?

My favored approach for creating splines is to start with fit points and then switch to editing the location of Control Vertices to fine tune the shape of the spline.  YOu can easily add addiitonal CVs to a spline by increasing its degree.

 

[vanowm]

Just now, lrm said:

What is the reason for adding the additional point?  It won't modify the spline unless you, of course, move it.

Exactly for that reason. It's for tracing an image, when I initially trace an image, I do it roughly, for speed. Later if I'm unable shape the spline with existing nodes, I add additional nodes so it can be more precisely fine-tuned. I guess it's a niche use-case...

 

[lrm]

Experiment with using CVs to edit the spline that you initially created with fit points. You may find that you like the control it gives you over the manipulation of fit points.

[vanowm]

Unfortunately bezier curves are problematic in some applications where I often export it to, so I'm stuck with fit splines for compatibility reasons.

 

But I do agree, CVs are more powerful.

[lrm]

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...bezier curves are problematic in some applications where I often export it to, so I'm stuck with fit splines for compatibility reason

It's not clear what you mean.  AutoCAD splines are typically B-splines whether created with fit points or control vertices. An AutoCAD spline is technically a Bezier spline if the number of CVs is one more than the degree of the spline and a NURBS (non-uniform ratonal B-spline) if a CV has a weight other than 1.

[vanowm]

Well, I don't know exactly why, but whenever I tried to import non-fit type of spline into patternsmith, it would really butcher that spline, adding millions of nodes or simply not following the shape.

[lrm]

It looks like Paternsmith has the limiitation that the imported spline must have fit points.  Interesting.

 

As you know, you can add fit points to an existing spline with splinedit Edit, Add and then use osnap nearest.  It might be quicker to use splinedit, Polyline to convert the spline to a polyline and then create a new spline by snaping to the vertices (all or a few) of the polyline.

In the image below a spline with 7 fit points was converted to  a polyline with a precision of 1 (red) and precision of 2 (green).  A new spline was then created from the polyline vertices.

  

Here's a closeup of the results.  Note that the red spline deviates slightly from the orginal spline.