[Bf-committers] Fluid particles refactoring

[Alex Fraser]

Hi Janne,

Thanks for putting together this proposal.

----- Original Message -----
> I've been refactoring the fluid particles recently, and before I
> actually start getting ready to commit this I'd like to get some
> feedback on my current progress and ideas.
> 
> http://code.blender.org/index.php/2011/02/particle-fluids-refactoring-under-way/

We have been using the SPH solver for engineering simulations. In our experiments, we often vary the fluid interaction radius independently from the collision radius. For example, if the size of a hole in a container mesh changes, I might want to make the collision radius smaller. Then again, it might make sense to make the interaction radius smaller too, so that the particles still flow nicely through the hole.

I suppose what I really want to do is change the resolution of the simulation without drastically changing the way the fluid behaves (e.g. double the number of particles, but maintain the same volume). If you can acheive this by changing the rest density at the same time as the interaction radius, I'm all for it. Will there be a way to find out what the interaction radius is, for the sake of writing reports? Also, what will the Advanced > Rest Length setting do?

One big challenge for us has been finding out how the parameters presented in the UI relate to physical quantities. The information doesn't seem to be available in the paper the Blender SPH code is based on:

    http://www.iro.umontreal.ca/labs/infographie/papers/Clavet-2005-PVFS/

Perhaps the simulation in Blender is unphysical. We intend to implement a classical SPH algorithm, i.e. one without the double density relaxation, to perform further experiments with. We expect it will be more physically accurate (although perhaps lacking surface tension), and easier to make multi-threaded.

Cheers,
Alex

-- 
Alex Fraser
Software Engineer
The Victorian Partnership for Advanced Computing