Bug: Grasshopper 1 - Rhino 6 Join curves does not join in the correct order

Noticed this bug recently which is messing up some of my workflows. You can see it described below. The Rhino 5 + Grasshopper .9xx worked fine. Can we bring back the old join algo to have better expected outcomes?

See here in Rhino 5, take a triangle, explode it, and join it. You will see it kept the segment order and start/end point in the original place which is expected behavior. (You cannot see the red because the green exactly matches it.

RHINO 5 + GH.9xx

The same operation in Rhino 6 causes the edge order and start/end point to go wherever it wants after joining, which makes no sense to me. Is there a reason that was changed?

RHINO 6 + GH 1

I use this workflow often for things like fitting degree 2 arc segments of polycurves and then rejoining, as long as I don’t add new segments the segment and start/end point always stayed the same as the input curve which causes me to now have to do a different operation in R5 and R6 for the same task, R5 being the obvious intuitive way where R6 requires now some additional hacking to get the seam point back to where it belongs. Please bring back R5 + Gh.9xx join :smiley: @stevebaer @DavidRutten

Here is the file for testing:
explode-join.gh (13.4 KB)

1 Like

The Rhino join method never made the promise that it would respect input ordering, but I can see that within the context of Grasshopper that would be desirable.

I can probably make it behave nicer by first trying to join all curves in the sequence to their successors. There might also be some information available in the core joiner that would allow for sorting the output to be more aligned with the input.

Logged under RH-48151.


I am also experiencing a bug with ‘join curves’ in Rhino 6 + GH. I am making very simple planar intersections with a simple shape and cannot for the life of me get the curves to join so I can make planar surfaces. Yet if I bake the curves and do a simple join in Rhino and re-input those curves it works perfectly. I don’t recall experiencing this in Rhino 5 + GH.


Hmm, maybe there was something corrupt with my file. After restarting it seems to be working more as expected. But still you can see in the middle of the definition I was using a join curves and if you check the ‘List item’ component, you will see a lot of lines are/were not joining for some reason?

Test Cut.3dm (65.2 KB)
Test Cut.gh (16.1 KB)