Bug / Crash gravity does not apply when I manually set the fixed delta time

[lufydad]

Hi!

Just set the solver's sleep threshold accordingly. This is the minimum kinetic energy above which particles are allowed to move. If you reduce the timestep, the kinetic energy during a single timestep will also be reduced, preventing any particle whose energy is below the threshold to move. See:
http://obi.virtualmethodstudio.com/manua...olver.html

You can set it to zero if you want particles to move regardless of how much energy they have. Note this may result in positional drifting/jittering.

Thank you a lot it seems to work, when I reduce the sleep threshold 
In my application the fixed delta time is entered by user, which sleep threshold should I use to be sure to not have this problem anymore and avoid drifting and jittering ? dt/10 is enough ?