Transformation of a polygon tunnel

[Matteo.309 (Matteo)]

Hey there!
Im am working with Grashopper since about 2 weeks so I’m still a beginner. I have a question regarding the geometry you find below. I want my “tunnel” of half-polygons to slowly open up and transform into a straight line which is on the top with grashopper. After many hours of trying and searching I didnt find a solution so I hope somebody here could help me out. (the desired transformation is also shown in a quick sketch.

Mister_Blackstars_ Problem.gh (13.5 KB)

Thank you all a lot for your help in advance!

[Joseph_Oster]

Believe it or not, the description in this thread is not as clear as you might think. Your previous thread was more obvious - can you clarify this one?

Trim 3D Curve Form with Plane

[WhatsApp Image 2023-03-02 at 22.29.58] Hey! I was searching through the Forum and also in the internet and didnt find any solution for this (I’m a beginner). Is there a possibility to trim/delete the part of my geometry that’s under the XY Plane (with Z = 0) ? that the form would be like in the picture with the Box. I will attach the GH file if needed Delete under XY Plane (internalized).gh (9.2 KB) [WhatsApp Image 2023-03-02 at 22.29.57] Thank you a lot for your time!

Maybe something like this?

Or would you prefer a smooth transition using Graph Mapper ? Like this:

Mister_Blackstars_2023Mar12a.gh (18.3 KB)

[Matteo.309 (Matteo)]

Hey, I’m sorry that the description was unclear, it is kind of hard to explain. I will try to model it in rhino somewhat quickly so that it will be more understandeable hopefully. Give me a moment. And thank you a lot for Reaching out!

[Joseph_Oster]

Look again at my post.

This is like a tower on its side and cut in half.

[Matteo.309 (Matteo)]

Hey. I did a quick model, of course its not precise and I would want to do that parametically with grashopper. And I want to apologize again for my unclear explanation, I hope this will clarify it:

Mister_Blackstars_ Problem.3dm (104.8 KB)

Each segment of the Polygon (except the top one which is horizontal) should rotate open until they are all paralell on the top.

[Joseph_Oster]

I hadn’t even noticed that your curve has a Z component. So the top of your tunnel is at constant height while the half polygons become flat… Looks a little tricky.

[Matteo.309 (Matteo)]

Yes, exactly. Then at least I didnt struggle at an easy task. Sadly also ChatGPT couldnt help me also after intense interrogation… Would you know any way for a solution for this, or do you think its maybe not really possible?

[Joseph_Oster]

Of course it’s possible! I know this isn’t quite what you want, it’s a quick and dirty approximation.

Mister_Blackstars_2023Mar12b.gh (20.4 KB)

I wrote some code somewhere on this forum that applies angles to multiple segments that might be great for flattening these half polygons “properly”.

[Matteo.309 (Matteo)]

That’s already much closer to what I want than I got ttrying to do this for hours!! Thank you a lot for taking your time to help me find a solution! I will try my best to learn out of your approach and maybe I will even reach my goal if I find your code somewhere. Really thank you a lot! have a great day!

[Joseph_Oster]

Here it is. Looks like it uses Anemone:

Bend polyline progressively with slider

Your model was way too complex for me to follow. My first effort (purple group below, polyline on the left) is not the droid you’re looking for… The second attempt (white group, polyline on the right) uses Anemone and is better since all the segments are equal length, as I intended. [bend_polyline_2019Oct1a] bend_polyline_2019Oct1a.gh (25.7 KB) If your polyline input has arbitrary length segments(?), it won’t do either, but the Anemone group could be adapted rather easily by replacing the …

And on the same page:

Bend polyline progressively with slider

I like this one much better. The white group (“bend it”) at the bottom does the heavy lifting with Anemone. It has two geometry inputs: 1) a polyline and 2) a rotation plane (‘rot_plane’). The ‘angle’ slider sets the rotation angle that applies to all segments. The first three groups are optional: ‘Consruction Plane’ (light blue) with Azimuth and Altitude sliders. ‘line’ (purple) that sets the origin and total length of a line. ‘polyline’ (yellow) with a ‘Count’ slider to set the number of…

[Matteo.309 (Matteo)]

Perfect! Thank you a lot!

[Joseph_Oster]

Not perfect at all! The Anemone approach looks futile to me for this.

Here’s a different way that’s not perfect either, as it has a hard spot between the scaled arcs and the rest of the half polygons. I think the best way to fix that is to recreate all of the half polygons using arcs before scaling the first eight at the end. An exercise for you.

Mister_Blackstars_2023Mar12d.gh (26.0 KB)

P.S. Here you go. It wasn’t that hard. It’s less code, simpler, so better in two ways!

Mister_Blackstars_2023Mar12e.gh (24.7 KB)

Version ‘b’ was a pretty decent approximation, for quick and dirty!

[Joseph_Oster]

This is getting a little carried away but it’s good to know how to do this, eh?

I used your curve (white) as a scale guide for tunnel height (Y in this case) and added a Value List switch (blue group) between the two methods. It could also be used for width but before doing that, a little more effort is need to make the white curve fair.

Full Size

Mister_Blackstars_2023Mar12f.gh (28.5 KB)

[Matteo.309 (Matteo)]

It’s great to know how to do this! also with every solution you come up I can learn from it, so for me it’s just great! And now it’s even quite what I want! so, really thank you a lot!

[Joseph_Oster]

Using plane intersections with a guide curve to scale height (and width) is a good trick to know but again, the results are only as fair as the guide curve. Instead, Graph Mapper was doing that fairing and you can get a very similar effect by manipulating it. This code is identical to version ‘e’ from yesterday with only small changes to Graph Mapper.

Mister_Blackstars_2023Mar13a.gh (20.8 KB)