minimal surface - cable net with Kangaroo

Hello, I am just trying to make a minimal surface cable net following the way described by Piker in https://vimeo.com/27484394.

I started with a simple hypar -like surface. Inner cables should be diagonally patterned with respect to the boundary, which is fixed. I considered inner cables and boundary as springs, and set the boundary points as supports. Yet, I get the "two-triangles" solution shown in the picture. I tried unsuccessfully to modify the values of the various parameters... what is wrong?!

Thank you!

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Permalink Reply by Nik Willmore on July 9, 2015 at 8:01pm

You have a mess. Your input mesh to the Kangaroo geometry input is itself an odd two-triangle quad mesh made by simply feeding an elegantly double curved NURBS surface straight into the Grasshopper mesh component, so Kangaroo has no real mesh to work on that corresponds to your springs, and that alone breaks it. Also, the Rest Length setting of 5 turns out to be way too high since it gives kinks all over the place until I turn it down to 0.1 after inputting a real mesh. You are also already starting with a minimal surface by how you made your NURBS surface that created such a nice double curve.

I haven't fixed your script, but did isolate part of it and manually made a starting mesh using the detailed Rhino settings for NURBS to mesh then used SoftMove to make a hat out of it, then extracted wireframe for the springs and added points to anchor, and it minimizes just fine with a low enough Rest Length setting:

Having to figure out how to make that smooth spike in the original mesh made me delightfully discover the Rhino SoftMove command after a Google search for "soft selection Rhino," I was unaware of! Wow, it's like clay modeling finally in Rhino. I was only able to do that before using the T-Splines soft selection radius option. This forum is great for rounding out my Rhino skills in new areas.