Combine / join 2 spline curves to a single one

[Anonymous]

There is "Break" operation in Sketch menu. So, I draw multisegment spline, then a line, and then split my spline by this line in intersection point. After that I have 2 connected splines.

So, the question is:

Is there the reverse operation except "Undo" to have these 2 splines to be single again?

Of course I can constrain the joint point to have these 2 splines Tangent, Smooth, whatever. But will not return the single spline. I.e. I cant apply "Close spline" to close the gap between 2 splines.

In addition, I faced with another problem when I have 2 connected splines:

It's tricky a bit to get "Tangent handle" for one of splines in joint point. For one of curves it appears just after clicking on the curve or endpoint. But for the second curve it does not appear after clicking on corresponding spline. Even if I click on the endpoint, the handle is shown for another spline. So, I have either to move the joint point, or click on other point on selected curve to see "Tangent handle" which I need. See screencast.

[HughesTooling]

No there isn't any way to make 2 splines back into one. For your second problem, the workaround I use is clicking a constraint from the sketch palette will make all handles show, hit escape and they stay visible.

Mark

[kieranjl]

Well I think this is getting close to the end of me using this program, how can the fusion team not get the basics right. The majority of CAD type programs have the ability to join splines including Autodesks own AutoCAD. Constraining the points is a half attempt as it does not allow the user to then offset as one single spline. Not to mention that offset doesn't create a second spline but just line without handles. 

[michallach81]

Guys @kieranjl @Anonymous can you tell us why do you need to join broken spline back together? There must be a "bug" in your workflow if you need first to break and then join the same curve.

I'm guessing that you rely too much on trying to solve everything within a sketch. No matter how elaborate shape you're trying to achieve you can get it by first defining primary surfaces then doing transitions between them, working beyond a sketch.

Now about splines themselves, Fusion to be able to join divided spline, would need to keep data about unbroken spline to restore. This how broken vs unbroken spline looks:

It's impossible to calculate precisely three different curves (after a break they have nothing in common) to create one. Can't be done, period.

Nature of a spline in Fusion makes impossible to edit any imported curves or even spline offsets since they are not build in same way.

[mroek]

There appears to be a minor bug when breaking a spline:

If I add a line that crosses over the spline, and then break the spline, a coincident constraint is added at the point of breaking. If I then delete the crossing line, the coincident constraint also disappears. However, there is still a coincident constraint between the spline ends (at the breaking point), and this is always hidden. It can be deleted by right-clicking on the connection point, but it isn't visible. I guess it should have been?

[michallach81]

I have to admit that displaying constraints in Fusion is messy and confusing. I was complaining about that already.

[Anonymous]

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@michallach81 wrote:

Guys @kieranjl @Anonymous can you tell us why do you need to join broken spline back together? There must be a "bug" in your workflow if you need first to break and then join the same curve.

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It was just an example. In real world they are not derived from the same spline.

But I still can't understand why Fusion is not able to combine 2 splines. It's possible to constrain 2 ends of different splines so that points behave as a single one. Just glue both sides into a single array of spline points. I do not require the exact precision. I just wand to have a single spline. As we have the functionality to delete spline points. It does change the geometry, but keeps the spline itself.

[michallach81]

It can't be done with Fusion spline. Layout for cv points is driven by specific algorithm, not by the user, a user specifies only through points. If you would join end points such layout would violate algorithms principles. 

[Anonymous]

Ok. Another way: I can insert fit points to first spline, then match them with corresponding points from second spline, then delete second spline. But why it can't be done automatically?

[michallach81]

It appears that you've matched curves... but in fact, you didn't.  From our user's point of view, it's good enough and we would like software to do the same, unfortunately, computers can't make arbitrary decisions. A bit of rhetoric, how many rational numbers you can find between 1,88888889 and 1,88888888? The answer is infinite. Not only we don't know based on what computers should choose from infinite possibilities, we can't imagine computer browsing through infinite possibilities in search of the right one.

[Anonymous]

I cant believe this. Splines cant be joined??? And some user said that is not nessesary? Come on...

If you have to draw a simetric spline, I draw half then mirror the other half right? And cant be joined?

So basic to me. Please @Anonymous consider the feature.

Thanks

[michallach81]

Did you read the discussion above?

What do you mean by joining splines?

You can join splines endpoints and ad constraints for specific curvature continuity, you can do it also for a mirrored spline.

If you need a single spline with symmetric shape, you can draw it as a single one and add a symmetric constraint to edit points and tangent handles.

@Anonymous, please consider not to proceed with a request for with only justification is an argument as such, "So basic to me".

[Anonymous]

How can I join splines endpoints? Sorry, my english is not good enough, maybe Iam missing something.

Thanks

[Claus_J]

Michael, you seem to know a lot about the subject with regards to Fusions definitions, however to users of every other spline based app, various cad apps including, you expect to be able to join two splines or join a line, an arch and a spline and tweek the shape of the combined curve. This is what I do all the time, it helps me design a single spline that has more geometric areas (that are based on lines and archs but altered afterwards). My favorite cad app does so without problems but it does change the spline points in the process, sometimes adding a lot of new points that require manual removal. However to me it’s still a great feature. I think you assume that the user will not accept that the join function alter the original splines, in my situation it’s acceptable. I know it’s popular around here to tell users their workflow is “broken”, my personal opinion is that users should be expected to learn and adapt to an app but the developers should also make an effort to meet peoples workflow expectations. I still find that I can recreate a model in Fusion as long as I modelled it before in an app that allows for some more free thinking. The question is, why would I want to do that?

[michallach81]

In principle, I don't agree.
For successful design, you must articulate your design intent in a form of meaningful geometry.

A designer must know what geometry could fulfill the requirement, which "design intent" implies and find the best available tool to use.

I guess that you know that such "joined" spline can only be an approximation of original shapes.

These shapes if meaningful couldn't be incidental, cv's layout is defined by the purpose it serves.

If we iterate the intent shape would update accordingly.

In MCAD (like Fusion) we doing it through features and constraints.

Whatever sets of features and constraint derived initial cv's layout, won't work for new "joined" spline.

You must ask yourself why your workflow forced you to "join" curves, and why you didn't create that shape in that form from the very beginning?

[Anonymous]

Thank you for the example. For me is like scratch my left ear with my right arm. Maybe the contrains are not feeling natural in my workflow. You put two constrains to make two splines to act like one. The reason is that you cant join them to be just one spline. In my opinion is a workarround for a missing feature.

Still dont understand it, the software is amazing, you can do almost everything with the splines but cant join them. 

Anyway, thank you again for the example, I will try it that way.

Regards

[michallach81]

We can discuss this further if you can give an example where you can't just draw a new spline that would replace current two splines. It must be a specific example so we don't argue over generalizations.

In my opinion, such new JoinedSpline tool is not a missing one, but a useless one. 

[Claus_J]

"You must ask yourself why your workflow forced you to "join" curves, and why you didn't create that shape in that form from the very beginning?"

Haha, yes that would certainly be a lot easier. But the real world is not like that, not mine anyway. The answer is the final design often comes from experimentation. And I would love to learn about workflow but the chance is I can teach more about it than I can learn, based on 25 years of work.

[n8bot]

An example of a valid workflow that requires joing two splines is when editing the outcome of a 2 axis generative design. The result is a sketch with lots of splines, and sometimes it's desired to join two when removing a connection to preserve geometry.