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Elliptical profile surface, thickness

Ignacio
Enthusiast
This is a (proof-of concept, test) zero-thickness morph, brought into GH from Archicad. Its profile is elliptical. It was generated in Archicad with a 0-thickness shell on an arc profile, saved as object, modified zzyzx, saved as morph, SEOed out openings, saved as morph —which produces a clean curved surface. With Check Solidity > Solidify the shape gets messed up. I would like to give it some thickness, with edge faces that need to be normal to the surface (I could get neither elliptical section nor normal edge faces with Shells; I may be missing something; I am a Shell noob).
I took it to GH but I can't find the GH command to give it some thickness (I am a GH noob), baked it hoping to find a Rhino command for reference but couldn't either (I am a Rhino noob).
I will be grateful for any suggestion on how to go about it.
7 REPLIES 7

Barry Kelly
Moderator
I know nothing about Grasshoper, but is there any reason why you did not add thickness to the shell in Archicad in the first place?
You can still SEO the holes in a thick shell or you can just use the 'Create Hole in Shell' command (select shell and right click) and draw the hole.


Barry.

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Ignacio
Enthusiast
Barry wrote:
is there any reason why you did not add thickness to the shell in Archicad in the first place?
You can still SEO the holes in a thick shell or you can just use the 'Create Hole in Shell' command (select shell and right click) and draw the hole.
With Shell I could not produce a continuous elliptical curved profile surface (as one gets with a circular arc profile) —magic wand segments make a mess of it all, especially at the junctions of vaults with different profiles. And I could not produce Shell edge faces normal to surface —I could only get them normal to contour plane, and parallel to opening axis. I may be missing stuff, I have never used Shells much.

Anonymous
Not applicable
1. ArchiCAD

I am not sure I completely understand the problem.
In ArchiCAD I got this with the shell tool using the magic wand to create the shell, then modifying the boundary of the shell. ArchiCAD uses meshes to approximate curved surfaced in the 3d window, so the junctions are a bit messy if you really zoom in. Is that the problem? In that case, I don't think there is a way to control the polygon count of shells.


2. Rhino/grasshopper

The geometry you get from ArchiCAD is a mesh. The biggest power of Rhino/Grasshopper is the use of NURBS geometry. It's a mathematical representation of geometry, with infinite precision.
To get the most out of rhino / grasshopper, first you need to draw a NURBS geometry over your ArchiCAD mesh, which I think is not a trivial task (at least for me, I am a beginner when it comes to Rhino)

In my opinion if you aim to use rhino/grasshopper you should start in rhino/grasshopper, produce the geometry as a NURBS, generate a mesh from that (you can control the polygon count of the mesh in rhino) and use that in ArchiCAD.

If you need to anchor the geometry to ArchiCAD geometry I'd rather use points than an actual mesh.

Szamosi Máté

Ignacio
Enthusiast
Szamimate wrote:
1. ArchiCAD
In ArchiCAD I got this with the shell tool using the magic wand to create the shell, then modifying the boundary of the shell. ArchiCAD uses meshes to approximate curved surfaced in the 3d window, so the junctions are a bit messy if you really zoom in. Is that the problem?
The original problems were
1) Archicad makes a mess of the elliptical curve when using any magic wand method (arc approximations are a mess, once you get precise)
2) which becomes dramatic when joining vaults with different curvatures (as opposed to crossing similar vaults).

In the vaults in the picture, the side vaults are circular but the corner vaults are slightly elliptical, and that rib between them must work. I ended up modeling that old-school, as if on a drafting table, drafting each shell as a series of straight segments, so that both sides match.

Then there was the openings’ frames problem. The opening side frames are skewed, they don't follow the maximum slope. I banged my head against every single possible Archicad element (beams, mophs) and GDL (TUBE, TUBEA, RULED), until I think I got it by GDL scripting the top and bottom sides, and POLY_s along the side frames, bringing those side polys into GH, extracting their perimeters, lofting them, and bringing them back into AC. It is not done yet, but I am fairly sure this will work.

All of this is really begginer’s GH work, so any suggestion will be welcome. But I think it's encouraging that GH got me out of this problem. (At this point I really hope nobody points at an AC-native solution.)

Anonymous
Not applicable
Hi Ignacio,
I think your issue with the skewed openings' frame can be fixed with the GDL XFORM command.
I recall using it years ago in a balustrade object I did for the Australian manufacturer "Sentrel".
You can find it here: https://www.bimobject.com/en-us/sentrel/product/balustrade
The object is not locked. You can dive into the code.
Also the GDL Central explains the command with some examples. Here.
With the XFORM command you can model the opening as if it would be plan and distort it with the command.
Hope this helps.

p.s.: Ok. Never mind. I see you want the sloping part of the opening to be arched.

Ignacio
Enthusiast
Braza wrote:
With the XFORM command you can model the opening as if it would be plan and distort it with the command.
[…]
p.s.: Ok. Never mind. I see you want the sloping part of the opening to be arched.
Thanks for pointing at XFORM anyway. I had never noticed it, if I ever saw it I must have thought it was something I would never need.

Anonymous
Not applicable
You are welcome Ignacio!
Yes. This is not very used command. But very useful. I think it is also used in the Railing Tool.
Anyway... It seems you are getting things done with GH. I will have to try it someday.
Cheers,

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