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Nvidia shows off new realistic water effect: Position Based Fluids

Nvidia shows off new realistic water effect: Position Based Fluids

PSB uses similar incompressibility and convergence to modern smoothed particle hydrodynamic (SPH) solvers.

Nvidia has unveiled its latest graphics animation enhancement in the shape of Position Based Fluids (PBF), a new realistic fluid simulation tool.

PBF builds on the long standing fluid calculation method know as Smooth Particle Hydrodynamics (SPH) and simplifies it to the point it can be used for real-time animation.

The challenge with existing implementations of the method is that to get sufficient realism requires enforcing incompressibility, and to do this requires having to either calculate at a high frequency (many moments in time) or high particle count, both of which are highly computationally intensive.

"SPH is sensitive to density fluctuations from neighborhood [sic] deficiencies, and enforcing incompressibility is costly due to the unstructured nature of the model...SPH algorithms
often become unstable if particles do not have enough neighbors for accurate density estimate"

"The typical solution is to try to avoid these situations by taking sufficiently small time steps, or by using sufficiently many particles, at the cost of increased computation"

The new Nvidia method, developed by Miles Macklin and Matthias Müller-Fischer, seeks to reduce the computational cost by "formulating and solving a set of positional constraints that enforce constant density". This method "allows similar incompressibility and convergence to modern smoothed particle hydro-dynamic (SPH) solvers, but inherits the stability of the geometric, position based dynamics method, allowing large time steps suitable for real-time applications. " In other words, it allows for a similar effect but using fewer particles and fewer time slices.

The PhysX paper on Position Based Fluids has been accepted for presentation at SIGGRAPH (Special Interest Group on GRAPHics and Interactive Techniques) 2013.

Furthermore, Miles Macklin has confirmed that since the SIGGRAPH presentation publication he has continued refined the rendering quality and has added “features like spray and foam”.

Video of the original SIGGRAPH submission and the refined version can be seen below.



PBF follows closely on from Nvidia publishing two other real-world animation enhancements, in the shape of Faceworks and Waveworks. Aimed at reducing the computational cost of accurately depicting facial animations and ocean waves, the two methods can, along with PBF, run in real-time on a single GTX 680.

How long it will be before we see games implementing any of Faceworks, PBF or Waveworks is not yet known but we certainly can't wait until they do.

15 Comments

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Snips 26th April 2013, 12:48 Quote
What I wanna know is ............Why harm a bunny?
Phil Rhodes 26th April 2013, 12:51 Quote
The problem with this sort of thing is that it looks great if you do a little two-foot-square box, but the moment you want, say, an ocean, or a lake, or frankly a smallish pond, it tends to become impractical.
barny2767 26th April 2013, 12:52 Quote
very impressive. it looks a little rubbery but much better than most water effects we have now. Skyrims rivers and streams with this would be awesome but kill all but the best setups.
LordLuciendar 26th April 2013, 12:58 Quote
Skyrim's water would kill my setup with this technology, and I've got a pair of GTX 670 4GB.

I wonder when processing ability will catch up to be able to render this in a large open world game like Skyrim.
greigaitken 26th April 2013, 13:19 Quote
so, how long till we can compute 10^12 particles and get the real deal.
phinix 26th April 2013, 13:51 Quote
Now, I want that in Crysis 4;) (Plus GTX "Titan 2" in SLI;)

So this isn't possible to implement in games, cause latest GPUs are not strong enough to pull like a whole ocean coast, is that correct?
Griffter 26th April 2013, 14:12 Quote
best water ive seens... now for how big can they take this. i dont want the next games to only have this effect in glasses and jugs cause the process is too complex the bigger you go.
Ayrto 26th April 2013, 14:55 Quote
Quote:
Originally Posted by phinix
Now, I want that in Crysis 4;) (Plus GTX "Titan 2" in SLI;)

So this isn't possible to implement in games, cause latest GPUs are not strong enough to pull like a whole ocean coast, is that correct?

They're plently fast enough already , they mention a "single GTX680 "...as they did with Epic's incredible Infiltrator demo. But they won't release any of these as benching demos :|. What's possible in some Nvidia 'low level' compute demo and what is possible in-game through DirectX with (flushing /sync) wait time latency, is another thing altogether.
derviansoul 26th April 2013, 17:09 Quote
very, very impressive simulation demo... i cant wait to see this in games. hopefully in about 2 to 3 years
ch424 26th April 2013, 19:11 Quote
Quote:
Originally Posted by barny2767
it looks a little rubbery

Yeah, that's what I thought too - though it looks better once they add the vorticity confinement towards the end. (whatever that is!)
DragunovHUN 27th April 2013, 02:38 Quote
Does anyone remember the PhysX water fron Ageia's PPU demos? Yeah, neither would I if I hadn't played the one single game that actually used it (Cryostasis).
loftie 27th April 2013, 10:56 Quote
Looks good, but they should know that all I've really taken away from this is that the Lindt bunny has a new job
Assassin8or 27th April 2013, 12:06 Quote
There is a big problem with this. This an nVIDIA PhysX paper. PhysX isn't going to be in any of the next generation games consoles as by all reports every console is going to AMD this time around.

This means that this technology is locked out of that market for 7+ years; unless we see a shorter turn around time by the consoles now that they could easily be backwards compatible due to them using commodity hardware.

That in turn will limit its take-up on the PC gaming platform side of things too which is a bit of a loss for us all.
DbD 29th April 2013, 09:42 Quote
Quote:
Originally Posted by Assassin8or
There is a big problem with this. This an nVIDIA PhysX paper. PhysX isn't going to be in any of the next generation games consoles as by all reports every console is going to AMD this time around.

This means that this technology is locked out of that market for 7+ years; unless we see a shorter turn around time by the consoles now that they could easily be backwards compatible due to them using commodity hardware.

That in turn will limit its take-up on the PC gaming platform side of things too which is a bit of a loss for us all.

I think you miss-understand. Physx is on the Ati powered xbox 360, and the PS3's cell and it'll be available for all the next gen consoles too. Just because nvidia refused to make it work for Ati powered desktop gpu's doesn't mean they can't or won't make it work for the consoles. Of all the physics engines physx is the most easy to port to new hardware as it's run on a multitude of different back ends in it's time. It will be there from day one.
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