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3D Modeling Query: Ruled Geodesic Tesslation of NURB vs. teh default method

ff33º

How can I Tesselate a regulated geodesic type structure from a NURB, shaped, lets say , like a football?

In RHINO and 3DS it sort of makes the patterns fairly loosely, I would like to do something similar to a Domed Space Frame Structures with more regularity than the patterns the softwares default to....and of course, without having to draw it in.

Any advice out there..perhaps I am using the wrong software?

 
Aug 13, 07 4:08 pm
_ks

quick way
rhino script with or without arch cut plug in.

long way
model by hand.

right software; but i'm not sure what you means by default. are you turning a NURBS object into a mesh and using that as your tesselation?

Aug 13, 07 6:39 pm  · 
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ff33º

Oh hey thanks,...so I am not so rhino script savvy yet and don;t see a plug in on their site for something like this...What is Arch Cut

Anyway, a client gave me a REVOLVED SOLID they want made into a mesh , but prefer the mesh to retain close to pure tetrahedral or icosahedral pattern.

by default , Isimply meant that there si a loose crinkly tessellation when i make a mesh out of it.


Thanks again.

Aug 13, 07 6:50 pm  · 
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ff33º

ooop.

I just found the Arch cut plug in...I'll try that out and see. thanks again _ks

Aug 13, 07 7:13 pm  · 
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Jonas77

i don't thing there is a way to tessellate in a geodesic pattern

use math luke.. and a mesh is never preferable unless it is to export at the last step

i have seen archcut be able to apply patterns to nurbs surfaces.

http://en.wiki.mcneel.com/default.aspx/McNeel/ArchCut.html

Aug 13, 07 7:15 pm  · 
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_ks

yeah...your not going to get something to magically tesselate into a geodesic object from a ruled surface...

without scripting it the only way i can think to get at a good result is to model by hand, which would be awful.

a possible method you might want to consider if you don't take the scripting route would be to use ArchCut to apply a pattern. Split the surface. Shrink all Trimmed Edges. Then take the smaller surfaces into Maya where you can locally extrude/modify on a more macro scale. This can give you a more geodesic object composed of small micro objects in a system. not totally sure what your going for.

hope this helps

Aug 13, 07 7:43 pm  · 
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garpike

This has been a recent problem for our office. We were asked to provide quad tessellations from our Rhino models. We were helpless with Rhino's simple mesh option. Unfortunately ReduceMesh isn't very smart either.

I hope one day NURBS catch on with the pro rendering crowd.

Aug 13, 07 8:17 pm  · 
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garpike

One trick I found was to build each plane manually using curves and PlanarSrf. Painful, but at least the trimmed surfaces that make a PlanarSrf are ready to go for simple meshing - i.e. not squeezed or distorted like a lofted surface (even the straight lofts) that can cause the meshing command to over think the surface and add more triangles.

Aug 13, 07 8:27 pm  · 
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FOG Lite

Is quad tessellations different from a quad mesh? I don't deal in the real of meshes too often so I don't know, but there is a quadrangulate mesh command. Probably doesn't have the power that you need though.

Aug 14, 07 11:07 am  · 
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ff33º

Although I am not so script savvy, i understand the geometry issue, I think.....I would think there would be a "plug in"..perhaps call it "Bucky" or something.

Optimum structural stability of a space frame, for instance would resemble a tetrahedral or icosahedral angle pattern wouldn't it?
...., despite the overall shape, yet it appears the software defaults use an algorhythm based on some other efficient rule of the shortest path between points on the space, with reference to the NURBS skin.

Which is fine mostly, ......but I guess the issue is that NURBS are "non-rational" by nature.....and yet some people want to see that proper tetrahedral pattern applied to unique geometries, even if all the all instances of the geometry cannot accommodate the proper angle. and I suppose, in turn, would change the original shape of the NURBS

The bottom line is a space frame designer wants the strongest geometry possible on the first run, without having to use IES software, ....so Bucky's angles are good rule of thumb, that someoen shoudl make a common "plug in" for.

Aug 14, 07 11:30 am  · 
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ff33º

....or should I say Plato's Angles.

Aug 14, 07 11:31 am  · 
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emaze

This is never a problem with 3D-H

Aug 14, 07 11:56 am  · 
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garpike

I like the Bucky command idea. Though the issue with tessellating a nurbs surface is to provide a clean package for translation into other software. Not really structure...

I'll look into the quad mesh command, though if I recall, it isn't what I think it is.

Aug 14, 07 1:07 pm  · 
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garpike

Archinect should sell 3DH t shirts.

Aug 14, 07 1:07 pm  · 
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ff33º

3D-H huh... so.... ,I just searched the threads and google, and I still don;t understand what 3d-h is,..Originally I thought it was software but, then it looks like methodology, and some seem to be devising a theory from it,..and other, perhaps a cult.

Where do I sign up?

Aug 14, 07 2:18 pm  · 
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garpike
http://www.archinect.com/forum/threads.php?id=55536_0_42_0_C

It is a bit of Archinect humor. I believe (correct me Per) that the H stands for honeycomb. Maybe one may you'll frustrated with it (him) like the rest of us. Beware.

Aug 14, 07 2:23 pm  · 
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rob(E)

try exporting it into form z because there are a couple good triangulate mesh tools there...i know form z is a pain but could be worth a shot

Aug 15, 07 9:18 am  · 
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ff33º

That is good suggestion...I remember Form Z in school...

Actually what I did recently was use the GeoSphere command in 3ds , after calculating size proportion and suitable scale. I stitched the selected domeys together and sculplted then into the overall form I needed.

It was a little backwords but I was able to retain a closer approximation of my Buckyismic structure for this shape, rather than deal with tesselation scritping nightmares.

oh, I also learned more about 3d-h,......uh?...yeah, ...okay?

Aug 15, 07 9:26 am  · 
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