yade-dev team mailing list archive

[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

Another attempt to summarize contact logic (to be added to the wiki when 
we agree on one logic) :
(Janek, please, have a look at the end of this message : question for you)
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1. Collider :

LOOP1 :
   if (isReal) isNew=false else isNew=true;

LOOP2 :
   if (BBoverlap && !found) insert;
   else if (!overlap && found && !isReal) delete;

2. Geometry Dispatcher

This dispatcher is setting
isReal = {
   if (there is a geometrical interaction || isReal)
       if (!interactionGeometry) intG = new();
       if (isNew) initialise geometry;
       update geometry; //(always)
       return true;
   else return false;
}

3. Physics dispatching

if (isReal) {
   if (!iPhysics) iPhysics = new();
   if (isNew) initialise physics;
   update physics;//(always)

4. Constitutive law

if (isReal || any other criterion)
{
   compute actions;
   isReal = true;
}
else isReal = false;

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This is the logic behind the "haveDistant" approach. It is still only 
partly implemented currently.

Pointing a few problems I just spotted :

A. In ISphere2ISphere4Geometry.cpp, we have (correct) :

if (penetrationDepthSq>0 || c->isReal){
       shared_ptr<SpheresContactGeometry> scm;
       if(c->interactionGeometry) 
scm=YADE_PTR_CAST<SpheresContactGeometry>(c->interactionGeometry);
       else { scm=shared_ptr<SpheresContactGeometry>(new 
SpheresContactGeometry()); c->interactionGeometry=scm; }


but in IBox2ISphere4Geometry.cpp, we have (WRONG!) :

shared_ptr<SpheresContactGeometry> scm;
       if (c->isNew) scm = shared_ptr<SpheresContactGeometry>(new 
SpheresContactGeometry());
       else scm = 
YADE_PTR_CAST<SpheresContactGeometry>(c->interactionGeometry);


Here, isNew means "has memory allocated", it should be replaced with 
if(c->interactionGeometry).

B. Currently, if "haveDistant" is activated, it seems isNew will not be 
set true by the collider even if !isReal.
This is surprising for me, and may be due to successive changes that I 
didn't notice.

Janek was using a "wasReal" bool before, to check if a contact was new 
in the physical sense (touch/detach/touch using the same pointer - you 
need to reset initialOrientation and such).

The proper way to do this, with the logic above, is to test isNew, 
provided isNew is set true when !isReal (be it in the collider or in the 
constitutice law).

The problem (and the question for Janek) : currently the snow 
preprocessor is using DistantSAPCollider, which does not turn isNew true 
when !isReal (the distant option in SAPCollider does not either, 
consistantly), and the "wasReal" flag disappeared. So, how does it work 
when the same pointer is used for two different (time wise) interactions?

Bruno



--

_______________
Chareyre Bruno
Maitre de conference

Grenoble INP
Laboratoire 3SR - bureau E145
BP 53 - 38041, Grenoble cedex 9 - France
Tél : 33 4 56 52 86 21
Fax : 33 4 76 82 70 43
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