Brep Frame/Shell Creation

Apologies for the generality of the title, but as I'm not sure the best approach at solving this particular concept, I'm not sure what the issue is exactly. I've hit a road block in every approach I've taken so far.

I'm using polyhedra breps generated with Lunchbox plugin, but I think the solution I'm looking for would be applicable to any closed shapes, symmetrical or not.

I'm trying to create a frame type geometry, similar to what can be created in 3DS Max with a Shell modifier. (for anyone familiar with that program)

From the attached image, I'm trying to create a solid surface connecting the highlighted (green) with the non-selected (red) faces.

Any help would be greatly appreciated, as I am new to Grasshopper and can appreciate I may be overlooking something obscenely obvious.

Thanks

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Permalink Reply by peter fotiadis on April 20, 2015 at 12:37am

Get this ... although easily doable with components (but I' don't work with them anymore)

Attachments:

polyhedracage_V1.gh, 14 KB

Permalink Reply by Zack on April 20, 2015 at 6:27am

That's perfect!

I'll have to study that script for awhile to truly understand what's going on, as my GH ability is definitely limited to components at the moment.

Thanks for your help

Permalink Reply by peter fotiadis on April 20, 2015 at 6:45am

Glad to help (in fact: "help", he he).

I'll try to convert this into GH components (not that difficult, it's just that is far easier for me to think with code instead with components).

BTW: the logic is very simple: find inner/outer brep Curve loops (for instance: cases with many holes etc etc) and "match" 1:1 curves from the inner "triangle" with the ones from the outer "triangle" (for the Loft thingy, that is). Then "combine" 4 breps per "triangle" into a closed Brep (polysurface in Rhino terminology).

best, Peter

Permalink Reply by Zack on April 20, 2015 at 7:04am

Thanks, I completely understand about the ease of thinking. I have a weak coding background and currently it is much easier for me to think with components than it is code.

I'm learning, just slowly. Ha ha and painfully it seems at times.

Permalink Reply by peter fotiadis on April 20, 2015 at 11:50am

No pain no gain my friend, he he.

BTW: Since you are after polyhedra: soon (or "soon") I'll post the final C# that does every imaginable dome (only 123,34 bugs remaining). In the mean time have fun with this as well:

https://www.google.com/url?q=http://www.grasshopper3d.com/forum/top...

Permalink Reply by Chris Hanley on April 20, 2015 at 3:02pm

Weaverbird is a plugin that lets you do some great stuff with meshes. In this case, maybe this simple approach might work for you?

It's only 3 components....but you do need weaverbird.

http://www.giuliopiacentino.com/weaverbird/

Permalink Reply by Zack on April 20, 2015 at 4:15pm

I really like the simplicity of that approach, especially since code is most definitely NOT my first language....

I have a question though, it seems the mesh created by weaverbird, even before the MeshThicken component is applied has some sort of mesh smoothing applied to it. It renders oddly, which isn't necessarily an issue for me, but it makes me suspicous that there may be a boundary issue as well that I'm not able to readily describe. An edge extraction shows all edges as lines, just as my original approach, but the actual surfacing seems off. WeaverBird is new to me, and I was wondering if you might have any idea the implications of the smoothing issue?

Thanks

Permalink Reply by Chris Hanley on April 20, 2015 at 4:30pm

good question...if you right click on the component and choose help, it does say that a "new mesh is computed with a higher genus."

I'm not entirely sure WB is the best approach, but at a quick glance of your sketch and description, I thought it seemed like a possible way to go. Try exploring a few different options and see what you get.

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