Kangaroo

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Kangaroo is a Live Physics engine for interactive simulation, optimization and form-finding directly within Grasshopper.

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Bending resistance + twisting resistance?

by Mårten Nettelbladt

Mar 6, 2011

Dear Group (and Daniel in particular I guess),

 

I'm trying to use Kangaroo for simulating 3d-bending of a developable ribbon surface.

Kangaroo has proved to be amazingly correct for 2d-bending (and 3d-bending of rods), but so far I haven't been able to get it right in 3d for a developable ribbon surface.

I've made a sketch (image + ghx-file) for a way to simulate bending AND twisting in Kangaroo. Rather than making a network of springs and bending-resistance-joints, this method creates a series of planes and rotates each step in two ways. The first rotation is bending. The other one is the direction of the bending (=twisting).

I'm thinking it would be possible to set something like this up with Kangaroo. Both bending and twisting would be series of "bending resistance" values fed into the Kangaroo. 

The definition looks a bit messy, but it's really quite simple. The tapeworm is a scripted version of this.

From physical testing, my impression is that the twisting resistance is much more powerful in a material than the bending resistance. A twisted material will most of all try to become a 2d-bend, and then it tries to become flat. With this in mind it could be interesting to set the amount of bend and twist resistance individually somehow...

 

Thanks a lot for any help!

 

Best

/Mårten

http://thegeometryofbending.blogspot.com/

 

  • up

    Daniel Piker

    Thanks Mårten,

    This does look an interesting approach and I would very much like to sort out something for torsional stiffness in Kangaroo.

    I've found this paper:
    http://www.cs.columbia.edu/cg/rods/
    and this guy's work:
    http://math.arizona.edu/~goriely/
    quite inspiring in this area.

    The relationship between the geometric torsion and material twisting of a rod is a bit more subtle than it might first appear. In this case of a strip rather than a rod though perhaps it will be more approachable because it has a clearer orientation.

    Thanks for sharing your ideas on this, I'll look into it and see if I can turn it into a force.
    1

    Mar 7, 2011

    • up

      David heaton

      Hello,

      Really awesome work!  I was wondering if there was an update to this thread?  Were you able to achieve the results you were seeking?

      Best,

      David

      Nov 23, 2015