Help: Error in result geometry

Tried rotating simple surfaces along an axis, it should’ve ended smoothly but it seems to have gone off its axis. I’ve used the center of the first surface, which I used to extract these multiple volumes, along the respective axis.
Any help would be appreciated!

Hi !

Please post your Grasshopper file with internalized geometry !

For (20.6 KB)

Hope this helps, thanks for taking your time!

Your box doesn’t have equal depth and width, which explains the fact that the first and end parts do not join.
You can either rebuild the box from a square base instead of a rectangle, or rotate the final part of your shape 90 degrees.

I also added an alternative contruction for the slices, to avoid the time-consuming Split Brep Multiple by moving the shape.
And finally there was a problem with your start point for the rotation line (there were two points), and a problem with the range of the third part (you set a domain up to 200, but the number of elements being 200, the last index is 199).

For (30.8 KB)

Hey, thanks for the help, the result is exactly what I wanted to do.
But I’m kinda new rhino, it’s only been a week since I started so a couple of things that you did I didn’t quite catch it, mainly two parts. If you have the time, could you tell me why you did this? some of these functions I still have to understand how they work, but if I understand the reasoning, it should help.

Instead of isolating specific faces using List Item, I sorted them along Y axis. This way, I’m sure the first surface in the list is the leftmost one, and the last surface on the list is the rightmost one. It does not depend anymore on the topology of the Brep.
The only way to do this properly is to identify a characteristic point that can accurately represent the position of the entire face, usually the center of gravity is a good solution (for curves, the middle point works the same).
Sort List works basically the same as sorting several columns in Excel at once, it sorts a list of numbers (Keys) from smallest to largest, and permutes corresponding lists (Values A here, but you can add inputs) accordingly.

I want to create Lofts between 2 consecutive sections. The Curves input of Loft is as list, which means it will loft all the curves given in a list, in order. So I can’t just give it the 200 sections, I have to group them 2 by 2. I need a list of lists, which in GH means a tree.
First, I use two Cull Index components, one to remove the first surface and one to remove the last surface. So I have two lists of surfaces :

These lists are grafted and merged, so each couple of curves end up in the same branch.
Branch{0} (srf 1,0) Branch{1} (srf 2,1) … Branch{198} (srf 199,198) - I should have inverted the inputs, so the curves would be in order
I deconstruct these surfaces and join the edges. The only problem of that is Deconstruct Brep adds another level of grafting (because a single brep has a list of edges, it must do that).
So I have to trim the tree one level down, so I get my two border curves in the same branch. Finally I do the loft.

I see on your screenshot that all wires are thin, you definitely should change that in Grasshopper display menu :


For more info on data trees :
The deal with Data Trees - YouTube

1 Like

Thanks for your explanation a bunch! I’ve not dealt with data tree before so i was pretty confused on hiw that worked. Will go through the link you sent me. Again, thanks a lot, i was stuck for a long long time.

So I tried using the trim tree function, I understood why it’s much better to form these lofts in this method, but when I do use the loft function, the last face pairs seem to have deformed. Don’t know why it’s coming like that, had followed your steps and values, but it didn’t come out right still, only the axes had changed when I started doing this but that shouldn’t matter, right?

Again, your help would be much appreciated!

Kisefos Museum (15.2 KB)


The boundaries seem to be mis-aligned. It works by ticking the Align sections option (I did that in the previous file also, forgot to mention it, sorry).


I noticed there is a much easier construction by moving the base rectangle instead as using Tween Surfaces. It removes a lot of components and tree management, and this alignment error. Have a look :
Kisefos Museum (6.3 KB)

Thanks a lot! I would’ve done the same but I might start experimenting which the alignment and shapes, so I think I’ll need to use that pairing between consecutive breps to create lofts. Again, thanks a lot!