Grasshopper

algorithmic modeling for Rhino

# How does Kangaroo work?

Hi all,

first of all, I am not an advanced user of Kangaroo. However, I am writing a masters thesis on various form-finding methods of tension structures and have also dedicated a chapter to Kangaroo as it has proven very useful for our project. Unfortunately, I haven't been able to find any concrete information on how Kangaroo actually finds the shapes that it does (not from a programming perspective, but more from a physical/technical point of view).

The Kangaroo manual (found here: https://goo.gl/AUL1w6) has proven useful but I am still unsure on the specifics. Is Kangaroo doing "pure" dynamic relaxation? So far that's my best guess, judging by imaginary point masses in nodes and solving the equations of motion.

Samo

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### Replies to This Discussion

Looking for information about mass-spring system.
Each particle has position, velocity, acceleration and mass (in its basic implementation, without angular movement). In each iteration, the forces and interactions are added to the acceleration of the particles. Then, the positions are integrated: the acceleration is added to the vemocity and the velocity is added to the position. The acceleration is set to zero and other forces are applied (collisions, restrictions...).
A force can be for example a spring, where two particles are applied the hooke's law, which in some case justs means to accelerate each particle so that they are located to a certain separation.
It's that simple. Everything else depends on a balance of forces and parameters, and it is that balance that can make it difficult.
If you are able to understand javascript, this will be very useful. But there are many more simple examples out there.
https://www.openprocessing.org/sketch/423250

There's an awesome set of lectures on Khan Academy by Pixar, where they do a very basic introduction to spring-mass systems to simulate hair in animation: https://www.khanacademy.org/partner-content/pixar/simulation

That might help.

as far as i recollect the form finding process for tension active systems in rhino is based on the open source dynamic relaxation method. Daniel has confirmed that in earlier discussions.

There is substantial info online for this method, and some of the earliest applications are by mike Barnes at Bath, UK. Amongst other methods that you might come across are the force density method (used by ixCube and rhinomembrane) which was used for formfinding of the munich olympic stadium, Natural Force density method which is developed by Prof. Ruy Marcelo Pauletti in brazil as also the update reference strategy method developed by kai uwe bletzinger.

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