Reshuffling the order of indices on a set of curves

Hi everyone,

I’m new to the forum, but I will try my best to follow the guidelines for new questions as posted by David Rutten and provide you with clear information.

My question is as follows;

I’m trying to create a set of reciprocal towers to connected to a double curved roof
reciprocal tower

For this purpose, I’m using octagons to create catenary lines to create two loft surfaces and cutting surfaces. At the intersection of these I create offsetted catenary lines which I then divide and connect in a spiraling fashion using relative item, I then interpolate between the control points to get the curved lines I desire.

So far, so good the only persistent problem that me and my colleagues haven’t been able to tackle is that the order of the curves, as visualised by making a Point List from the startpoints, is irregular.

15 out of the 16 towers will list as 0,2,3,4,5,6,7,1. Which isn’t perfect but workable.

It’s the tower of branch {1;0} that;s giving problems, as it is listed as 1,3,4,5,0,6,7,2.

My primary question: How can I deduce the error and prevent this difference in the order of the curves from happening in the first place.

If that’s not feasible, my backup question would be: How might I go about changing the order of the indices without changing the physical location of the curves.

Thank you very much in advance!

forumquestion_order (49.7 KB)


I’ve added a few things to the definition.

  • Order the start curves
  • Order the curves again after joining the polylines. It could be avoidable but to the cost of a very complex data tree management, so might as well keep it.
  • Removed all those Partition List and replaced everything by Trim Tree to keep a nice data structure all along.
  • Removed the Loft offsets, and intersection ? That is not working anyway on my file. I think simple offsets are enough.

I hope I haven’t destroyed the entire design :sweat_smile:

forumquestion_order (43.2 KB)

1 Like

Hi Teddy,

It’s OP here from my personal account (I work for Olav, so I was logged in on his account).

You certainly live up to your name!
That was a very sophisticated, dare I say, magical, solution to a problem that was really halting our process.

I took notes on:

  • your use of arethmetic to create a plane for a circle to sort the startpoints of a group of curves along
  • using list item to reorder a whole list of indices
  • using trim tree to control the data structure

Thank you also for the offset on surface, that will help in the future elaboration of the design in which we will use double poles for added structural integrity.

Thank you for help and swift and clear reply.

Have a great day!