[Bf-committers] Sub frame calculations for particle systems done!

[Raul Fernandez Hernandez]

Hi all :)

  Stability is one of the most desired feature of a simulation and in
particle systems is a must have. The particle fluids exhibit random
explosions (which I think could be reduced because in older SVN
revisions that doesn't happen) and in general the particle systems have
a leaking trough wall containers behavior when the container rotates.
(think of the typical wine glass falling example :) )
  As a suggestion from Jahka and several members of the community I have
implemented particle subframe simulations not just for particle fluids
but for the whole particle system.

  Subframe simulations greatly increase the stability of the simulation to
any desired level, it basically perform a user defined number of
pre-simulations in between frames, allowing finer grain sims, and a nice
side effect of it is that now particle-surface collisions could be
properly captured so there's no leaking effect when containers rotates.

  Subframe simulations do increase the calculation time proportionally to
the number of sub-steps, so the user have to made a trade-off between
stability and simulation time. But the good news is that there's now a
lot of methods to reach stability in the particle systems so a
combination of them will help to get very low substeps (even none) to
get stable simulations and proper particle collision detection very
fast.

I have recorded several videos of the feature in action, and as soon as I
get connected today I plan to upload and publish the patch.

                                                 Regards Farsthary