[Bf-committers] Patch: Adaptive time step for fluid particles

[Matt Ebb]

What he means is that if you run two sims with the exact same settings, will
the results be exactly the same? This is pretty important.

cheers

Matt


On Tue, Jun 7, 2011 at 12:05 PM, Alex Fraser <adfries at vpac.org> wrote:

> ----- Original Message -----
> > From: "Shaul Kedem" <shaul.kedem at gmail.com>
> > No, I mean is it deterministic?
>
> >From one run to the next, yes, you should get the same result.
>
> In terms of being predictable, I did some tests with the TwoPipe demo, in
> which water drains through a hole (you may need to increase the fluid
> interaction radius to see this effect). With zero subframes, it takes a long
> time to drain; with more subframes, it tends to take less time (time in
> frames, not computation time). However, it starts to converge for subframes
> > 3 or a Courant target < 0.2, and barely changes beyond subframes = 8 or
> Courant target = 0.1. So it seems to become more accurate with smaller time
> steps, but you should rarely need to go beyond those values.
>
> The adaptive subframe code gives a stronger guarantee that your simulation
> will be stable, but it's not predictive, so for some simulations a constant
> time step is still more appropriate.
>
> Cheers,
> Alex
>
> --
> Alex Fraser
> Software Engineer
> The Victorian Partnership for Advanced Computing
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