Creating Tent Roofs

[chstech]

I am trying to recreate a twin pole tent. For those that don't know what it is, there are 8 center poles arranged as 2 rows of 4 poles each. Mine are at 30' high. The out side perimeter is at 10' high. The tent top itself is not a straight diagonal, but sags downward. I have tried the Drape Tool, but either it is the wrong tool to use or I am not having any luck.

Any ideas?

[islandmon]

Try using "Revolve with Rail" procedure:

[Kaare Baekgaard]

If you need to construct a real life tent, I suggest, that you break the job down into creating the 5 different 1/4 side types individually.

As far as I can see, it is 5 if the tent is to be manufactured as a single piece of canvas. Loft each side from the curves, that define the side(s), intersections, midsection and top point. You may have to break each side into two or more lofts. You can also try with the create surface from curves comand, but it is my experience, that it does not give adequate control.

If the tent is ideed constructed as several individual elements , each section can be lofted from two nurbs profiles - a square, a superelipse and as top a 3D locus point. The sagging will come from how high you place the middle profile.

Islandmons approach is OK for illustration purposes, but does not take into account how canvas behaves under tension.

Good luck

[G_Hannigan]

I've done this using NURBS surfaces. You can add Vertices, move them and change their "pull" to control the tent's shape. It can be time consuming, but it works.

[G_Hannigan]

Sorry, I forgot how to include an image in my post.

[Ray Libby]

It's in the FAQ.

[islandmon]

Just used a basic catenary curve revolved around the center support post to illustrate a simple technique. No attempt was made to model the real world tensile characteristics of fabric.

[G_Hannigan]

http://www.home.earthlink.net/imagelib/s...le=VW_NurbsTent

[Ken]

I don't know what's a "twin pole tent," but another idea which shows smooth fabric-like curves is to subtract a sweep from a solid, then convert to nurb. Ungroup, delete parts as necessary, then adjust individual vertexes later in the OI to fit:

[propstuff]

I think this is sort of what you want, but I haven't achieved the pointy bits at the top of each pole very well.

You can see in the image the series of NURBS curves it was lofted from.

Editing the curves will give a better result.

Unfortunately the result of this process is a Solid Addition. I.E. a series of individual NURBS Surfaces rather than 1 whole surface. This makes editing the finished shape a real pain.

I think Kaare's method will probably give the best results, but a fair bit of work.

That is; there's no easy answer to a shape like this. :-/

HTH

Edited September 23, 2006 by propstuff

[panthony]

Arch.Ken has got the sweep down...however all those guys in California can't afford to park the merc. in a real garage...

[chstech]

George,

Can you tell me the steps it took to make that??

Thanks!!

[chstech]

Wonderfull input here. It sound s like with anything in life there are many ways to do the same thing.

The image that propstuff has shown is exactly what i am trying to do. But what are the steps to create it??

The best luck I have had so far is using the Drape Tool.

Thanks

[G_Hannigan]

Unfortunately, the drape tool is more like "shrink wrap".

I will post some suggestions later. In the example, I played around with one nurbs surface. Then I mirrored it and played around some more. I don't know what your finished tent should look like, but it might be easier to break it into compnents and then put them together.

George

[propstuff]

Drew,

In my image you can see a set of profiles (NURBS curves) passing through the shape.

These were used with the Loft tool.

The centre one was done first, then the pointiest one.

Then the smaller ones to the outside were made by duplicating the pointy one and stretching.

-Group temporarily, stretch, ungroup, tweak the verticies.

-and moving to the side to control the drape of the Loft.

For a symetrical object, always do one side and mirror.

Note that the peaks in my shape do not stop at the points of the curves, but keep on sweeping up past them. This is normal and would need to be controlled with more curves. I don't think this technique will ultimately give the best results.

HTH

[G_Hannigan]

Here's another:

http://www.home.earthlink.net/imagelib/s...le=VW_NurbsTent

[propstuff]

George,

this second one seems closer to what drew wants.

It looks to me like spheres and cylinders subtracted from a loft.

What method did you use?

cheers

[G_Hannigan]

Nicholas,

NURBS Surfaces only. No Booleans.

1. Created 30' pole grid as guide.

2. Rectangle-Center to Center between 4 poles.

3. Extrude Rec, Thickness = 0"

4. Modify/Convert to NURBS. Move to top of poles.

5. In OIP:

- Move: Vertex Only

- U Degree = 2, V Degree = 2

- Check "Show Vertices" at bottom

6. Adjust Z value and weight of vertices until it looks ok.

7. Mirror/Dupe to the side. Adjust vertices away from the "seam" so the outer edge is at 10'.

8. Mirror/Dupe to opp side. Select all three, Mir/Dupe down length of layout.

9. Similar process for ends - Mir/Dupe to other end.

You could add tie downs ropes around the edges, play with the vertices and create the look the fabric stretching.

George

Edited September 25, 2006 by George Hannigan

[G_Hannigan]

Here's another:

http://www.home.earthlink.net/imagelib/s...le=VW_NurbsTent

[islandmon]

Excellent design & rendering, Mr. "PT" Harrigan...

[propstuff]

You could add tie downs ropes around the edges, play with the vertices and create the look the fabric stretching.

George,

nice job, but you haven't added the knots at the tent pegs, or the seams in the canvas. ;-D

So, you ended up with 12 individual surfaces? or did you get them to join up?

The reason I ask is that when I've had objects made of individual surfaces like this, and tried to edit one corner vertex, it's distorted the whole object.

In this example, if I have pulled, say, one of the outer corners of the tent further outwards; the other edges of the Corner Panel would pull away from the mating edges of the adjacent Side Panels, and a gap would appear between them :-(

Getting adjacent NURBS surfaces to join up (with the Combine Connect)is itself a complete pain which fails more often than not, and using Add Solids gives an object which has limited editing options...........

How would you approach this?

N.

[G_Hannigan]

They are individual surfaces. The Mirror/Duplicate process was the key to keeping the joints tight. In this case there are only 4 different components, (top, sides, corners and center ends), all created from the original top panel. I only grouped them after they were made. This allows editing without the distortion you mention. I had the same problem on my first try.

Maybe I'll start a wish list for a Circus Workspace!

George

[G_Hannigan]

This little exercise shows why I would like to have multiple views (Top, Right, Iso) as part of VW. It is very tedious switching from top view to isometric to see how it looks and back to top to adjust.

George

[propstuff]

Having the conventional 4 window view would be a bonus.

But I do find the direct view keys from the keypad quick and easy.

cheers george

[G_Hannigan]

That's where my Nostromo Speedpad comes in handy - lets me keep my right hand on the trackball.

This was a fun challenge - learned a few tricks.

George