# Offsetting folded panels for fabrication

Hi there!

So, I have this structure:

and I need the surfaces to be 14cm thick. I tried offsetsrf and Weaverbird_thickenMesh…the first looked like this:

Weaverbird_thickenMesh looked better, but the thickness wasn’t the same:

I gave it a 14 cm thickness:

But then when measured: (distance between the planes)

it was different.

I’d be grateful for any hints to solves this. Thank you!
Rhino files is attached
Panels.3dm (505.1 KB)

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@piac can tell you for sure, but my guess is that the WB offset distance is at each vertex - that the vertex is moved 14cm along its normal direction.

If you want to move each face, and then remake the meshes, that gets harder. This is because offsetting each face an exact distance parallel to the face normal will result in corners that don’t line up. This means you’d need to then find the intersecting edges of each plane, and rebuild the mesh - and even then, there might be additional faces needed to get exactly what you want.

For example, the 4-face mesh shown in this image offsets to create a peak at the top that may not be what you have in mind. Offsetting a set of meshes with valence 5 (where 5 faces meet at a vertex) may result in an additional surface showing up at the tip.

I don’t think there’s a straightforward way to get what you’re after without modeling the offset by hand.

Yes that’s what it does.

Section 3.2 of this paper has a very clear explanation of why constant distance face-face offsets with 1:1 correspondence of vertices are not possible for triangular meshes, except the trivial case when the shape is a sphere or plane.

I went through this same process when trying to make a geodesic dome (WIP). You don’t have to model the panel thickness for fabrication… what you need is the bisecting angle on each edge of each panel and probably an ID tag on each edge. Then you would cut the panels with the correct angle on each edge.

I used mesh topology to create a list of panels with an angle for each edge. This can give you adjacent mesh faces and you can then calculate the angle between them.

I was attempting to make the edges of each panel so needed slightly different info for fabrication but the principle is the same.

I can’t find the link now, but there was an excellent plugin for doing this sort of fabrication too… anyone?