# Kangaroo2 help with surface drape

Hello,

I need some help with this grasshopper definition. I am trying to create a tensile surface that responds to three points. I followed a tutorial but the results aren’t exactly what I was looking for. It also has a center point that I don’t want there. I attached the definition for help.

Is there a way to have the drape surface only respond to three points or corners of the rectangle rather than 4?

Kangaroo tensile structure.gh (24.6 KB)

Hi @skat,

Damn, I’ve rarely seen such a messy file!

Do you mean like this?

Looks quite weird! Doesn’t it?
You might want to reconsider your goals here!

Kangaroo tensile structure 2.gh (11.9 KB)

something along the lines of that. I am trying to recreate this model I’ve made

This is by no means a definitive Kangaroo model, just a triangle with three support points instead of a rectangle with five.

Kangaroo_tensile_structure_2020Feb23a.gh (22.3 KB)

That video is useless.

Thank you so much!! this is what I was looking for

Here’s another solution with multiple tensile structures, like in your video:

Kangaroo tensile structure 3.gh (21.8 KB)

@DanielPiker, do you know why the individual meshes stick together, even if their goals are properly segmented? Shouldn’t there be gaps visible between the meshes (like in the video above)?

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As I recall, Kangaroo works better when you Triangulate the mesh - purple group. Again, this is not an expert Kangaroo model!

Kangaroo_tensile_structure_2020Feb23b.gh (22.9 KB)

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@diff-arch - the meshes get joined because they have coincident points.
If you wanted them to pull apart, you’d need them to start slightly separated like this
(my addition in the blue box)
Kangaroo tensile structure 3 (1).gh (26.2 KB)

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Nice, thanks for this insight, Daniel!

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A rule of thumb is the minimum anchor points for a tensile structure ought to be 4 and the boundary conditions should be such that you achieve double curvature. In this way your tensile structure can cary load. 3 points define a plane, not double curvature. For a structure to be called tensile it has to be under tension. Furthermore the final result must be in force equilibrium.

Unless you wish to create water colectors on purpose (which will totally happen with your model under a combination of rain and wind or snow load) or you wish to rectreate structure failure… I strongly advice you to reconsider your current idea… or at least never build it. Thank me later.

Yes, I know all of this from ingene-ering 101! Who rattled your cage?

It’s OP’s design, not mine! I just played around with Kangaroo and tried to help with the simulation. Can we just have a little fun here please?
Oh yeah, and you forgot to mention that either way it’s impossible to get a perfect triangle with tensile structures.

Thanks for pointing these things out, but who even mentioned that this is meant to be building/pavillon? Maybe it’s a temporary art piece inside a museum, or an ephemer outside installation to show, how environmental forces interact with man-made structures!?

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Hit reply on your stuff by mistake instead of the Skat dude… Anyway… Don´t take stuff personally kid.
One has to admit it to you though. It takes a whole lot of creativity and mental gymnastics to come with a deffence of something you know is not working properly. Respect man… respect

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Hello, I used the same definition you uploaded but changed it to a hexgrid, I was wondering if you know how I could add a center point to it that also works with the surface??

Hexagonal grid.gh (25.1 KB)

By the way, with the same caveat as before (I’m not a Kangaroo expert and might be wrong), it looks to me like the mesh behaves better with a higher ‘Min’ count (Custom Mesh Settings) and using Triangulate - see white group:

Hexagonal_grid_2020Feb27b.gh (27.4 KB)

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would you know if there’s a way i can combine grids within the definition? Like the HexGrid and TriGrid for example and basically have this same tensile surface thing happening?

I’m not sure what you mean? Is this a question about Kangaroo or about how to use GH components?

Hexagonal_grid_2020Feb27c.gh (31.3 KB)

This annoying message from the forum is telling me to bow out of this thread. Maybe someone else?

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more like taking these two for example and plugging it in to the definition

but with a more i guess unified grid