Creating a faceted structure

Hi, I would like to share a problem I have been struggling with for a few days. I'm trying to make a supporting structure which will be built from in-situ concrete to support a faceted form for the interior of a Chapel design. I'm currently this testing on the model below.

Following is the sort of thing I'm after but with much cleaner geometry.

I have tried to achieve this is Grasshopper by extruding the internal and external planes and then performing a boolean operation to trim the structure.

As you can see the geometry is still untidy and there are many overlapping parts at corners which causes problems when moving into 3DSMAX. I would really appreciate it if any of you experts out there could give me some advice of how I might achieve this better result. I think I need to trim the resultant geometry but I have no idea how.

Or maybe there is a different process altogether that would be better suitable. I considered something like the boxmorph but I can't see how it would work on triangles.

Thanks in advance!

Attachments:

chapel_definition[autosave].gh, 16 KB
rhino.3dm, 1.8 MB

Replies to This Discussion

Permalink Reply by taz on February 10, 2011 at 10:57am

That's a tough one... we'll see what other people have to say but I don't think there's a foolproof method.

It's a bit tedious, but manually you could boolean union two pieces at a time at each node and work sequentially. You'd still certainly need to do a lot of trimming. Maybe this could be scripted.

With GH, it would be a bit difficult, but if you can develop a (repeatable) routine that works manually, perhaps you could use GH to partially automate the process...

Permalink Reply by Matt Harrisson on February 11, 2011 at 11:09am

Hi Taz, thanks for the reply.

That's an interesting idea to extrude all then boolean union to get the nodal joints and then remove the joints from the whole thing again and then join what's left. I'll have a crack at that and see what happens.

I had a deadline and ended up just hacking my way through endless triangulating in sketchup to get something that could be presented. Thought I'd share it with you:

Permalink Reply by taz on February 11, 2011 at 4:09pm

Cool stuff!

Don't hurt me, but I forgot that WeaverBird can now do a mesh offset (similar to shelling), so converting to a mesh and back is not too bad for your faceted surfaces. Mesh booleans don't seem to work too well in GH which is why I ended up using [Trim Solid].

Permalink Reply by Matt Harrisson on February 13, 2011 at 8:15am

Wow, that looks great, nice and clean. I've downloaded weaverbird and tried to put together that definition you posted there. It mostly makes sense to me but I'm unsure about those symbols at the top left of the evaluate surface and extrude components. What are they exactly? Thanks, Matt.

Permalink Reply by Marios Tsiliakos on February 13, 2011 at 9:22am

Hi Matt,

In the first case you just reparametrize each surface so you won't get any funny results from the evaluate component. In the second case Taz just sets the expression of the input parameter to [-D*2] meaning reversing the direction of the offseting vector and duplicating its magnitude. you can achieve that in any component by rightclicking without having to apply a function component to get the new values. I hope now everything is clear.

Nice design by the way.

Regards/p>

Permalink Reply by taz on February 14, 2011 at 2:26pm

Yep, Mario's explanation is pretty clear.

The [Eval Srf] component is simply to grab a surface normal from each faceted surface. Reparameterize (the squiggle symbol) normalizes the UV domain from 0 to 1 and specifying a UV value of {0.5, 0.5, 0} is just to evaluate the surface in the middle of the domain.

Alternatively you could do this:

The use of the expression -D*2 is also just a shortcut to save some components. You could do the same thing without an expression by using vector [Reverse] and [Multiply].

Permalink Reply by Matt Harrisson on February 14, 2011 at 4:18pm

I understand what is happening in this part now, thank you. I have followed your definition on a small practice section and everything seems to work perfectly up until the trim component. The trim either fails completely or leaves some residue from the base geometry. Can you shed any light on this?

Here's what occurs:

The Facets: