Deformation with kangaroo

Hey all,

I've some problems with Srings and deformation in Grasshopper and Kangaroo.

Frist of all: in my model the lines bounce to hard back from the ground plane. So the lines get all blue (from the tension) and very long.

Secondly: the lines can change lenght, how can the lines keep the same length all the time? I tried to solve this with the Spring rest length, but it doesn't work.

And finally: if I move a point in Rhino, I want the rest of the points and lines to respond on this and the whole model deforms. Is this possible?

Below you can see the Rhino and Grasshopper file which I use.

Does anyone has the answers? Thanks.

Kind regards,

Sjors

Attachments:

deformation.3dm, 70 KB
deformation.gh, 11 KB

Replies to This Discussion

Permalink Reply by Hannes Löschke on June 14, 2012 at 5:07pm

several things:

1) your truss is statically stable and sufficiently supported by the 4 base points. the CollideSrf Force will never even apply.

2) never play with default values you don't know about. default damping is 10, "reset" solution becomes unstable with damping of about 25 or more. (your blue line and all)

3) every spring with finite stiffeness will change length. physicallly built structures will settle under load (several centimeters depending on load conditions). So fixed length segments are nonsense in phyiscal world in the first place. If you want segments to keep length, increase stiffness or rest length over desing length (think as initial length without load..) Keep in mind: large stiffness will cause instabilities in the simulation.

4) you can move referenced anchor points and the model will update. Introducing an additional anchor, like, at the top, will fix your model to this point. It will move, but will also try to apüply forces to this anchor. Anchor points need to incide with simulation nodes, when kangaroo is reset. So be sure to move your additional anchor to it's original position before you reset.

Permalink Reply by Sjors de Graaf on June 20, 2012 at 11:56am