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Re: R: Re: Contact detection



I coming back again about the contact detection, actually in SDEC there was the choice between a contact detection by grid and the simplest method were "every particles was checked with every particles" because detection by grid is not always the fastest method, that depends on what you are simulating:

1/ When the global geometry of your problem is more or less constant during the whole simulation (for instance: simulation of a triaxial compression on a dense granular assembly) the detection by grid is quite good, because you build the grid once at the beginning of the simulation and you use the same grid during the whole simulation. In addition you don't have to update the list of the neighbouring particles too often.

2/ When the global geometry of your problem is not really fixed (for instance an avalanche of particles in a very open space: you don't know a priori were the avalanche will propagate) it is not sure if the detection by grid will be good, because you will have to update often the grid to follow the particles or you will have to make an inital very large grid, whereas only few cells of the grid will be used at a given time step for the detection.

Chiara, I read your mails quite quickly so I don't remember if you have specified the kind of simulation you want to do, but in my opinion contact detection is good, but not always ;-)



Janek Kozicki a écrit :
Václav Šmilauer said:     (by the date of Mon, 16 Nov 2009 09:46:52 +0100)

In another words, Olivier (and you) didn't bother to google out articles
on that and thought he was the smartest guy.
yeah. That time there was a LOT of other stuff to bother about, than
colliders :) Paint me ashamed ;>
I am not saying you are to be blamed, but Frederic, as supervisor of the
project, should have managed that.

I recall his point of view: SDEC has a lot slower collider (IIRC:
it was "check everything with everything"?. Some SDEC user could tell
us). And so Frederic was very happy to see how much faster SAP is :)

Luc Sibille

Université de Nantes - Laboratoire GeM UMR CNRS

IUT de Saint Nazaire
58, rue Michel-Ange - BP 420
44606 Saint-Nazaire Cedex, France

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