Truss from a surface and a curve.

I'm new to Rhino and Grasshopper and I am having a few problems with a definition I have been trying to write.

I am trying to create a truss, from a surface and a curve. I have managed to array the curve around a point and on to the surface and create the top and bottom tubular sections of the truss but I am struggling with creating the diagonal braces between the top and bottom members. The section of the definition that I have created to make the bracing works on a curve in a single plane (2D) but it all goes wrong when the curve is in more than one plane (3D). As you can see if you open the attached files, most of the diagonals miss the top and bottom sections and aren't in a regular pattern. It took me for ever to get the definition to this stage and despite my efforts and many hours of fideling I can't make it work.

Please help? The files I have been using are attached.

Also I would like to create pneumatic ETFE type pillows between the trusses, but I have no idea where to start with that. Any pointers would be greatly appreciated?

Thanks

Mark

Attachments:

truss from surface and curve.ghx, 686 KB
truss-surface and curve.3dm, 4 MB

Replies to This Discussion

Permalink Reply by Jon Mirtschin on April 9, 2010 at 3:33am

Looks cool, I'd like to help, but I'm a bit hectic at the moment.

Have you seen this example using my plug-in?
http://geometrygym.blogspot.com/2010/02/structdrawrhino-utilised-in...

ETFE cushion behaviour (or similar simulation) for meshes is something I have some base code for, but haven't linked into my Grasshopper plugin yet.

How urgently do you need to get this modelled?

Cheers,

Jon

Permalink Reply by Mark James on April 9, 2010 at 4:47am

I have looked at StructDrawRhino briefly previously, but didn't really have time to play with it and had forgotten about it when doing this. The example looks very interesting but again the curve only seems to be in one plain? Would it work on a 3D curve? That is where I'm getting issues. I've had a quick look at the script but it might take me a while to get my head around it! I presume the script is creating the geometry and StructDrawRhino is then being used to create the actual profiles of the steels?

I have until 17 April to try and get the structure bits sorted and then another week before I need to get the ETFE stuff sorted.

I have a rhinoscript for ETFE cushions but it requires a perimeter polygon for each individual cushion for it to work and it is going to take time I don't really have to manually draw them all. So even if there is just a way I can simply and quickly turn the curves I already have in grasshopper into individual polygons, which I can then use the rhinoscript on that would be a lot of help! I have tried but I got nowhere!

Thanks, any help is greatly appreciated!

Mark

Permalink Reply by Jon Mirtschin on April 9, 2010 at 5:38am

Sweeping along non-planar curves can cause problems, but we're a good chance (or can try to address it if we're not successful straight up). I'll take a look as soon as I can.

You can use the sdrCurveNetwork component to create polygons (by specifying an offset of 0 and a radius of 0), but the curves have to be split at the intersections (I have an existing command for that too, but I didn't add the component for that yet, I will try to this afternoon or weekend). Without promising, I'm confident I can have the ETFE enabled within your first deadline.

Cheers,

Jon

Permalink Reply by Mark James on April 9, 2010 at 5:59am

Sounds great. I'll have a look at it again when I finish the other project I am currently trying to finish off!

Thanks again.

Mark

Permalink Reply by Jon Mirtschin on April 13, 2010 at 9:58am

Hi Mark,

Here's my first stab at generating some trusses. I think it's a nice looking project, well done.

Looks like I was a bit heavy handed with the chord profile. You should take a look at the 2012 stadium screen capture on the blog to see how to control the profiles etc, or let me know. The difference in chord lengths means the division lengths should be adjusted, I didn't have a chance to do this. There is the capability to specify division points at curve intersections, I haven't connected that yet. I'd suggest disconnecting the sweep profiles when testing adjustments. Be paitient while the file computes, with the projections and non-planar sweeping it's computationally heavy. Also, you'll need the latest version of StructDrawRhino which I am building and uploading right now. http://www.geometrygym.com/downloads

Hope it helps, I'll be starting to think about the cushions.

Cheers,

Jon

Attachments:

trusssurfaceandcurve mod.3dm, 709 KB
100413 trussfromsurfaceandcurve mod.gh, 41 KB

Permalink Reply by Mark James on April 13, 2010 at 11:00am

Hi Jon,

Seems really good. Much more successful than my attempt. I had a quick look at it after a few issues with installing the new StructDrawRhino, but I got there in the end!

Will have a play with it properly when my desktop has finished rendering some other stuff, my laptop moaned and groaned a bit and didn't really like working it all out.

Thank you very much, your input has been a great help.

Mark

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