How to make certain particles "invisibles" to others?

Hi Luc,

what do you mean by invisible? No interaction between certain particles? In that case I would try mask/groupMask [1].

HTH
Klaus

[1] https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.Body.groupMask

Yes, by "invisible" I mean that they won't interact with other (and that will happen during the simulation so their state would change from "visible" to "invisible").

I tried to find more information about the groupmask but the description is kind of short in the doc ("Bitmask for determining interactions" ).

Is there any example where I could grasp more precisely the idea?

Thanks

Not sure if there is a good example. Long story short it is a bit wise comparison. Here a short example assuming three bodies:

O.bodies[0].mask=1 # 00000001 -> corresponds to 1 in the binary system
O.bodies[1].mask=2 # 00000010 -> corresponds to 2 in the binary system
O.bodies[2].mask=3 # 00000011 -> corresponds to 3 in the binary system

In this example, O.bodies[0] and O.bodies[1] would not interact whereas O.bodies[2] would interact with both.

HTH
Klaus

Salut Luc,

There is a discussion about this topic here:
https://answers.launchpad.net/yade/+question/240275
it helps to make things clearer even if it is not complete...

Best,
Luc

Le 27/10/2016 à 13:58, Luc Scholtès a écrit :
> Question #403534 on Yade changed:
> https://answers.launchpad.net/yade/+question/403534
>
> Status: Answered => Open
>
> Luc Scholtès is still having a problem:
> Yes, by "invisible" I mean that they won't interact with other (and that
> will happen during the simulation so their state would change from
> "visible" to "invisible").
>
> I tried to find more information about the groupmask but the description
> is kind of short in the doc ("Bitmask for determining interactions" ).
>
> Is there any example where I could grasp more precisely the idea?
>
> Thanks
>

--
Luc Sibille
Université Grenoble Alpes / IUT1 de Grenoble
Laboratoire 3SR UMR CNRS

Tel lab.: +33 (0)4 76 82 63 48
Tel IUT: +33 (0)4 76 82 53 36

OK, many thanks guys.

I see now more clearly how to use groupmask.

I am still not sure this would be the best way to deal with my problem since the particles that I want to be invisible from the other "visible particles" should also be invisible from each others (I don't want them to interact with anything).

Using groupmask, I would thus have to define a different bitmask for each of them, making sure they cannot interact one with each other... I am not sure this would be practical since I should then define the bitmask equal to 2^i for each of the i-th invisible particle and thus would probably be limited in the number of particles I can actually set as invisible...

I hope this was clear enough...

Luc

Hi Luc,

I think you just need to add this:
https://yade-dem.org/doc/yade.wrapper.html?highlight=avoidselfinteractionmask#yade.wrapper.InsertionSortCollider.avoidSelfInteractionMask
to get the behavior you'd like.

Jerome