algorithmic modeling for Rhino

New Mighty Kangaroo: Collision between Brep and points problem

Hi all,


I am currently working with the new kangaroo and I can't manage to make the collision module to work: I am trying to use the same logic as for balls collision with springs, but kangaroo turns to red... and it drives me crazy...

I saw on the new manual that this point will be treated later, but well, if it is possible to have a little clue before the new version, it would be wonderful :) 







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You just want stuff to bounce around in a box?  Try this!

The definition, FYI.


It's mesmerizing to watch...

Of course David did this like 5 years ago, but if you use meatballs it will look like a lava lamp. Equally mesmerizing.

Nice, thanks Taz. By the way, the simulation will run a bit faster if you use mesh spheres instead of surfaces.



also fun to use David's value tracker...

Hi Thibal,

You are doing everything right, the only problem is that the inputs to Force objects are coming in on different paths and are not flattened. To fix it just switch on flatten for this input.
We are going to make it so that any paths here get automatically flattened in the next version, as I know this is unclear, especially when there no obvious data trees going in.

Thanks for your answers Taz and Daniel! I must have thought to the flatten, I just remember you said in your manual to flatten this input but I forgot...


Taz: in the definition with metaball, what is the component you used in the "c" variable of the scaling component? Some kind of slider to extract a point on a line? Is it a public component or a home-made stuff of yours? 


I have a little other question concerning collision: if I understand well, a distance-based collision is the only solid collision available for the moment? Or can we input some boxes instead of spheres and use a different relationship/law specific to breps? (I was using the spheres as bounding solids for boxes actually..)




Yes, the only 2-way collisions currently available are distance based.

(there are particle-brep collisions but these are 1-way only - the breps are not affected)


There's actually a lot of tricky stuff involved in doing collisions between arbitrary 3D rigid bodies well and at decent speeds. It's usually one of the most complex parts of physics engines for games and there are many entire books devoted to the subject. (take a look at this table of contents for an idea of the difficulty of the problem)

So I decided to leave this alone for the moment, as I think it could eat up a lot of time that would be better spent developing other aspects.


For very approximate collisions you can always place several spheres at some of the vertices of solids made of springs.


Thanks for these informations Daniel, I think for further experiences on precise solid collision problems I will try to do it with solidworks or catia/DP, as they handle solid mechanic simulation it may be an answer to the problem (maybe create some data exchange link like maya2GH). Or maybe there is a tip with galapagos, by calculating the multiple positions of the object and then cull the solutions when a solid intersection is happening... If I have the time to experiment these solutions I will post the files here. 


Thanks again for your answers,


[Point on Curve] 
Thanks! I never saw it before..






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