Grasshopper

algorithmic modeling for Rhino

Following on from parts 1 & 2

Once we have relaxed our mesh, and stopped the timer, we can click the Data Dam to pass the result to the next part of the definition:

The Stripper* component breaks the mesh into long strips 1 quad wide.

*I did make an alternative icon for this, but opted for the tamer one in the end ;)

The Unroller component goes along the strip face by face, rotating it into a single plane.

Note that this component will still give a result even if you supply it with non planar quads - it will just fold them along a diagonal. However, if the faces are significantly non-planar, then it won't work as well for fabricating from a smooth strip of sheet material, so it is better to try and make sure your planarizing in the relaxation part is working well.

The Unroller component also has a T input which allows you to unroll only part of the mesh at a time. This is mainly for animation purposes, and most of the time you will probably just want to leave it set at 1.

At the moment the unroller is limited to working with open strips, so if your strip forms a closed loop, you will have to split it first. Later releases should include an automatic 'loop snipper'.

The final part of the definition then takes all these strips, orients them into the XY plane, and does some very basic layout.

It's then up to you to label, add tabs, nest, laser cut and assemble!

Because of the subdivision, each strip should have an even number of quads, which can also be useful for generating interlocking tabs by offsetting alternate groups of edges. I'll try and post an example of this soon.

I hope this is helpful. It was my intention when making this that it could be a relatively quick and easy way of making smooth curved structures out of sheet material, (I'm thinking card, polypropylene, metal, thin plywood...) with a lot less fixing/connecting work than doing a similar shape with individual panels.

Thanks to all the participants in these long-running threads:

http://www.grasshopper3d.com/forum/topics/how-to-create-nodesbone

http://www.grasshopper3d.com/forum/topics/skeletal-mesh

which inspired this work, especially some of the comments by Ivan Kiryakov, Wiktor Kidziak, Giulio Piacentino, Andrew Haas and Mårten Nettelbladt.

*note also that the meshes generated using this definition can be used for developable strips, because they have the even-valence property.

I was also inspired by these papers:

http://www.cs.jhu.edu/~misha/Fall09/Liu06.pdf

http://www.geometrie.tugraz.at/wallner/strip.pdf

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Replies to This Discussion

Thanks for the explanation.

This tutorial was amazing man!!! Great work. 

Hi, 

Thank you for this amazing tutorial. I was wondering if there is a way to create developable strip surfaces that are like this: https://noumena.io/draft_synthesis-of-strip-pattern/

If so, I would be grateful if you could guide me through it.

Thank you.

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