yade-dev team mailing list archive

[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

Regarding the displayed deformed cell, I think it would make sense to 
display bodies in a rectangular cell too.
Sizes need to be updated, but the rest is as you like : you can see 
grain passing in a rectangular window (wrap the current euclidian 
coordinates to a rectangular cell), or display the deformed cell as you 
seem to do now (wrap unsheared coordinates and display bodies at 
position totalShear*(wrap(unshear(x))). The second looks better perhaps, 
but needs more computation.

Do you have working scripts for periodic compression without shear? The 
ones in trunk return errors. I'll try to look the current implementation 
and think how it can be generalised. I finally understood why the 
collider need to be adapted to shear, btw.

Thanks.

Bruno


Bruno Chareyre a écrit :
> Vaclav, you can paste this code after l.90 in cell.cc (the modified 
> version).
> Some more numerical experiments. It is in fact the comparison between 
> one step with dt, and 100 steps with dt/100, for the same velocity.
>
> Bruno
>
>
> ///Again the same, but decomposed in n=100 increments : the constant 
> volume distorsion is represented more accurately  : (det(F)-1) is  
> O(1/n). This example shows what will happen in dynamic simulations, as 
> long as we don't have large transformations in only one step.
>    C._totalShearTrsf = Id;
>    dt /= 100;
>    C.Hsize = Matrix3r(C.size[0],0,0,
>            0,C.size[1],0,
>            0,0,C.size[2]);
>    previousHsize = C.Hsize;
>    for (int i = 1; i<=100; i++) C.updateCache2(dt);
>    cerr<<endl<<"incremental volume change (depsv) "<< 
> (C._shearTrsf)(0,0)+(C._shearTrsf)(1,1)+(C._shearTrsf)(2,2)<<endl;
>    cerr<<"real incremental volume change (V(t)-V(t-dt)/V(t-dt)) "<<
>        (C.Hsize.Determinant() - previousHsize.Determinant())/ 
> previousHsize.Determinant() << " =(?) 100 x " << 
> (C._shearTrsf+Id).Determinant() -1 <<endl;
>    cerr<<"total volume change (epsv) "<< 
> (C._totalShearTrsf)(0,0)+(C._totalShearTrsf)(1,1)+(C._totalShearTrsf)(2,2) 
> - 3 <<endl;
>    cerr<<"det(F) - 1 = "<< C._totalShearTrsf.Determinant() - 1 <<endl;
>    cerr<<"real total volume change (dV/V0) "<<  
> ((C.Hsize.Determinant() -initV )/ initV) <<endl;      dt *= 100;
>
>
>
>
>
>
>
>
> Václav Šmilauer a écrit :
> > Hi there,
> >
> > I commited a few changes for the period cell shear. For now, just the
> > underlying Cell class is in place and OpenGLRenderer renders the sheared
> > cell (no collisions yet, in particular). You can have a look at
> > scripts/test/periodic-shear.py, it looks pretty :-)
> >
> > For the python interface, it will have to be changed in some meaningful
> > way, so please don't use it in your script, it is not stable. In
> > particular, instead of O.cellSize and O.cellShear, we will have O.cell
> > returning a Cell object, which will contain the properties, like in c++
> > (O.cell.size and O.cell.shear, perhaps some more as needed).
> >
> > If you feel sad and run gnome, press Alt-F2 and run the command "free
> > the fish" (without quotes).
> >
> > Cheers, Václav
> >
> >
> > _______________________________________________
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> >   


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