yade-users team mailing list archive

[kan <nicessgg@xxxxxxxxx>]

Hi, Dear All,

I readed the code in PersistentSAPCollider, but I am sad because I found I
can not understand how the program works to find the potential contacts?
could you please give me some hints about the details of the
detectalgorithm? It seems a position of a particle is decomposed to
xBounds,
yBounds, zBounds, then sort it, then compare the x,y,z in these three
xBounds, yBounds, zBounds vectors? but how does it work? I still cannot
understand.

Thanks a lot.

Kan.



On 2/14/08, yade-users-request@xxxxxxxxxxxxxxxx <
yade-users-request@xxxxxxxxxxxxxxxx> wrote:
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>   1. Re: What is the contact detecting method used in YADE?
>      (Kien Dang, Mr)
>
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> ----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 13 Feb 2008 14:58:03 -0500
> From: "Kien Dang, Mr" <kien.dang@xxxxxxxxxxxxxx>
> Subject: Re: [Yade-users] What is the contact detecting method used in
>        YADE?
> To: <yade-users@xxxxxxxxxxxxxxxx>
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>
> Hi,
>
> you can look at the engine persistentSAPcollider, this engine update the
> pair of potential contact by sorting bubble bounding volume method, and then
> check if the bounding volumes are overlap or not, if yes, the pair of IDs is
> assigned to the interactioncontainer (transientInteraction in Metabody).
> Note that they are only potential contacts since only the bounding volumes
> are checks, and then, pairs of particles are checks again in
> InteractionGeometryMetaEngine to determine if they are really in contact or
> not. If they are really in contact, flag isReal in interaction is true and
> then the contact geometry is built for each real contact.
>
> Hope that I can understand your question clearly,
>
> Take care,
>
> Kien Dang
> -----Original Message-----
> From: yade-users-bounces@xxxxxxxxxxxxxxxx on behalf of kan
> Sent: Wed 2/13/2008 2:56 AM
> To: yade-users@xxxxxxxxxxxxxxxx
> Subject: [Yade-users] What is the contact detecting method used in YADE?
>
> Hi, Dear All,
>
> I am just losting myself in understanding the contact detecting method in
> a
> DEM.
> could you please give me some instruction or explaination about what is
> the
> contact detecting method used in YADE?
> It is easy to detect if two contacted particles becomes non-contacted
> again
> by check the distance between their center with their radius
> sum(radius1+radius2, assume both of them are sphere) because they know
> each
> other when they are in contact an have stored their neighbors relationship
> for each other. But, how do you know whether two will change from
> non-contacted conditions to contancted condition----because they do not
> know
> each other before then come to contact, do not tell me that you check each
> pair in all of the particle---it works but the time cost is toooooo
> expensive .
>
> Thanks.
> Regards.
>
> Kan
>
>
>
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