circus tent......need help

[Davidm]

I need to make an old fashioned circus tent, 180' x 60', with 8 main support poles. In other words these poles stick way up, 26' above the 12' vertical sides. From the outside the tent looks like a collection of 8 cone shapes, sort of.

Also, it would be nice to end up with a hollow object that I could "fly through" on the inside, and look realistic from the inside looking upward.

Any ideas ? Right now we still have version 9.5. But if you have any ideas for either ver 9.5 or 10, please let it fly. Thanks.

[Biplab]

I have seen circus tents created using loft tool in the past - Julian Carr had created a tent with 4 internal poles. The result is a bunch of NURBS surfaces. Most of the work in this is in creating the cross-section curves for the lofts. If you have 8 poles - you probably need to use the loft tool 8 times and each loft should have a 3D locus point (corresponding to the end of each pole) as the end of x-section curves.

[Guest]

David,

If you have the 3d power pack installed, you can do this with nurbs surfaces.

If you do not have it installed, please update to the latest version of VW and install the 3d power pack.

If you look on our page where people showcase thier drawings, there is a drawing of a circus tent on there.

Basically, you would draw a flat shape representing the tent top. Convert the object to a nurbs surface. You would then need to add the u and v degree vertices to the nurbs surface. You can then change the z height and the wieght of the vertices to give it that taught or pulled effect. Kind of like sticking a toothpick under a piece of tissue paper with the flexibility of a latex balloon. If that makes sense.

There is a tutorial that comes iwth the 3d Power Pack explaining how to add and move u and v vertices on a nurbs surface. The file is a PDF file you can leave open while going thru the exercise to get you on the right track.

[Guest]

Okay . lofting is probably easier.

[Biplab]

Yes, there will be gaps if you just reshape the interior points of surfaces - this is because the surface that you are reshaping is a trimmed NURBS surface and after reshaping the surface, the trim curves are mapped to the new surface parameterization - resulting in a gap.

I think the circus tent was created using loft tool - where the surfaces were created by interpolating a bunch of tent x-sections - with a point x-section at the top end.

[mark@custom]

I posted this question under the u and v vertex topic, but it appears that this is a more related topic.

I know about creating a surface from nurbs curves, also how to set up the u and v vertices and how to move each independant vertex. However, I've found that on non-rectilinear shapes the perimeter of the nurbs surface distorts when an interior vertex is raised above the others along the z axis. I've tried using the weight function to get around this - only seems to make things worse. I see the circus tent illustration on the VW 3D PP reference pdf - how was the perimeter of the "tent" structure held within plane?

Thanks,

[ 01-14-2003, 12:25 PM: Message edited by: mark@custom ]

[Andrew Bell@NV]

quote:

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Originally posted by Davidm:

I need to make an old fashioned circus tent, 180' x 60', with 8 main support poles.

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I would suggest looking at the Create Surface From Curves command. Make NURBS curves connecting the outer poles to the peak poles, with the cross-section you would expect, and other curves for the edges connecting the outer poles. Then use that Create Surface From Curves command to make nurbs surfaces from each enclosed region. You can either make duplicates of the curves that you need in more than one surface, or use the Extract Curve tool to make a new copy as needed.

The weakness of this approach is that your tent isn't "smooth" between the pieces, if that's the effect you desire.