GH - Why doesn't Join Curves Join Curves? Bug?

Hi again,

This has made me confused more than once, namely that the Gh Join component doesn’t actually Join its input curves, unless adding an extra Join component at its tail, like so :

Fig1. Notice how the first Join outputs two (2) curves, only the second Join actually Joins the two curves :

This must be a Bug, no? Tested and confirmed the behavior in both Rh5 and WIP (May 23, 2017)

// Rolf

does this happen in the basic example of having two lines which are then joined? because for me, it works as expected :

Hm, I get proper result when making fresh lines like you :

But, then I tried to “Flatten” the output of the two Line components feeding the input curves to be Joined, and then it started to Join at first attempt. Should that really be needed? < scratching head >

// Rolf

Yes, this is an essential part of how GH works. Join joins curves by branch, that is to say all those are in a list at the same branch level. This way, you can have a tree with many branches and only the correct corresponding curves are joined for each branch level.

If you are wanting to join curves on different branch levels, you are going to need to either flatten the different lists, or use something like PathMapper to re-route one or more of the branches so that they are at the same level.


1 Like

OK, it makes perfect sense.

I just didn’t think of the fact that everything “multiple” is a list by nature, and that all lists in Gh (probably) are of the same type, which has branches (overlooked that). It’s intuitive once you come to think of it that way. :slight_smile:

// Rolf

Hi out there,

I have a similar problem. Two curves shall be connected by a blend curve and than be joined.
I tried hopefully all options to change directions as I thought that might be the problem.
The join items are grouped below,
I tried to minimize the items but wasn’t sure where the mistake is.
So please forgive the size of this.
Join curves (126.4 KB)

Thanks for your help.

As above, flatten the input to the Join Curves component.

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thanks for the fast answer, thought I tried that also, but it works.

Sir, I just came here to thank you!! I was suffering this for hours

thank you so much, I am new to grasshopper and this saved me so much.

Hi, It’s my first day learning grasshopper and I’m having a problem with the join curves command.
For some reason it does not allow me to join two curves (parameter) with the command. The line that connect the canva ot the “curve” with the canva of the “join curves” disconnect if when I connect another canva.
Basically, the join curves command does not allow more than one curve to join it, so I can’t join the curves.
I looked some videos and no one seems to have this problem

You have to hold down the SHIFT key when adding the second wire. And both wires must have the same data tree path. Same applies to all GH components.