yade-dev team mailing list archive

[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

>   (Don't use Newton::gravity though, it breaks something in your
> script and I'm still investigating).
>
It is not related to the new Newton::gravity, it only revealed another
bug in eigen's quaternions.
In your script, Klaus, the clump sometimes disappear, did you notice? It
is because the axisAngle conversion of clump members orientation is nan
from time to time (especially just after impact, when the roation of the
clump is very small).
For some reasons, this feature breaks the time integration when the
gravity engine is removed and replaced by Newton.gravity=-9.81.
Adding a GravityEngine in the loop with gravity=(0,0,0) fixes the
problem, although it doesn't touch orientation at all...
I'm really scared of eigen's quaternions. It's not the first time they
give weird behavior.

The conclusion is: if you have problems with clumps rotations, add a
null gravity engine in your simulation... :(

Bruno