Volumetric Particle Flow | Hacker News Reader

Volumetric Particle Flow

david.li

236 pointsrinesh35 comments

There is also a follow-up demo by the same author called Disintegration, with skinned animated mesh driving particles:

Looks reminiscent of a fairlight demo from 2009 http://www.youtube.com/watch?v=ezltebzdgjI

They did two much more impressive demos[1][2] with this technology, including drawing complex geometry using only point sprites, on DX9(no compute shaders). It's remarkable that those five year old demos could easily do flows, shading and blending on milions of particles in real time, while this JS version starts dropping frames at 262K.

[1] Agenda Circling Forth http://www.youtube.com/watch?v=L5w7Gh7WBjw

[2] Ceasefire http://www.youtube.com/watch?v=Grqb1aIa_4s

As cool as those are, I've always found Numb Res to be the most impressive:

http://directtovideo.wordpress.com/2011/05/03/numb-res/

( http://www.pouet.net/prod.php?which=56900 )

( https://www.youtube.com/watch?v=LTOC_ajkRkU )

Subtle presentation a great effect, but this bit from the demo's nfo is kind of insane:

    3d smoothed particle hydrodynamics with a fully-featured solver,
    supporting surface tension, viscosity and collisions with arbitrary meshes. 

    rendering as metaballs converted to triangle meshes with marching cubes. 

    simulating around 250,000 - 1 million particles per frame and generating & rendering
    several million vertices per frame during triangulation. 

    except we wanted to do it in realtime. on a consumer gpu. on vanilla directx 9.
    no cuda/compute, no geometry shaders. (they'd probably be too slow anyway.)

    with everything else youd expect from a modern demo going on around it and on top.
    the best possible lighting, depth of field, post-process antialiasing.

    twice. (for stereoscopic 3d.)
    with style.

The page also shows that sometimes what you think is hard is easy and what you overlook is the really difficult bit:

> The problem with SPH in realtime is it’s really really hard. The simple explanation of the algorithm is: “take all the particles near my particle and perform some force exchange between them”.

At this point I was expecting a long discussion on all the clever tricks they have found to calculate the force exchange between thousands of particles in a snap. And instead...

> The force exchange is easy; the “all the particles near my particle” is a bitch. On GPU it’s even more of a bitch; and in 3D it becomes an order of magnitude more of a bitch.

> [...]

> The problem is simply the neighbourhood search. You end up with a variable amount of fast-moving particles affecting each particle, where it’s hard to pick an upper bound – so the spatial database is hard to construct. If you solve the neighbourhood search, you can solve SPH.

I wish there was a HN thread to geek out about the demo scene. Was just watching some of the Mind Candy DVDs recently and going down memory lane.

Worth a link to his extensive blog posts http://directtovideo.wordpress.com/category/fluid-dynamics/

yeah, Smash used curl noise too. He got some crazy particle counts back then. Awesome dev. https://directtovideo.wordpress.com/2009/10/06/blunderbuss/

This is really cool. Is there a reason it looks a bit out of focus, even with millions of particles? Some kind of blurring effect, maybe?

Using Safari, which isn't supported, but I wanted to say kudos to the author for adding a video for unsupported browsers. That was definitely a neat feature that many WebGL demos overlook!

Safari is supported, you just have to enable WebGL. I am using it just fine with Safari 7.

How is it that there's (what appears to be) c source code in there:

https://github.com/dli/flow/blob/master/flow.js

That is GLSL, the language pixel, vertex (and other) shaders are written in.

I've no idea what all you folks are using, but in my hands (linux amd64 i5 8Gb debian/jessie) this is a very impressive website in that it straight-out crashes firefox/iceweasel (31.1), stymies firefox nightly (35.0a1), and leaves google-chrome (37.0.2062) declaring that it couldn't be loaded. (just a theory: i'm running nouveau on my nvidia, as the last blob wouldn't compile)

Surprisingly, Firefox performs better than Chrome for me.

i7, 20GB RAM, Quadro K2000M, Fedora 19, latest stable of both Firefox and Chrome.

On fedora 20 with binary nvidia drivers it works flawlessly both with firefox and chrome up to 2M particles on a gtx 680.

Works okay on an old Core2duo Macbook with Nvidia 9400M GPU in Chrome 37.something, so it's likely the driver.

i3 with Mint 17. Looks good[1] up to 131K on Chrome (37.0.2062.120). I don't know if your configuration is wonky or your machine is just old, but it actually is a very impressive website.

[1] http://i.imgur.com/x8f40v5.jpg

My laptop's fan has has hit overdrive and beyond.

Works well on Ubuntu 12.04 with Chrome (core i7, 8 Gb).

I have no idea in what is going on or what this is about, but adding the Video for unsupported browsers is a great idea.

Really wish there was convention to annotate link titles that immediately bog the CPU.

I made the mistake of hitting the 1m button.. Bad decision.

Good suggestion. But honestly the words volumetric, particle, and flow didn't give you a hint?

I think it's about time I jump on the js bandwagon then.

This has really nothing to do with js. I could mechanically translate the demo to Haskell or Python and it would perform equally well, as all the heavy computations are done on the graphics card and those are given in a C like but implicitely parallel shader language. All this really demonstrates that the webgl bindings to opengl have minimal overhead. One thing that is impressive, how you can trivially and more or less declaratively define a user interface using the browser rendering engine, whereas a similar user interface in a simple opengl demo would have to be very primitive or use a third party library. This makes such webgl demos much nicer to interact with compared to a similar demo written in c, but the actual code is nearly the same, since it is mainly library calls to opengl.

Very cool! Smooth as silk at 524K on my GeForce GTX 650 Ti and Chrome 37. 1M makes it a bit choppy, but still pleasant.

I see only some sphere with a spot. What is going on there?

Very smooth - running on Safari 7 on an i5 and a 660ti

Works, but my MBA 2013 i5 shooted up to 98C. :o

Looks like blood in a vein on the default xD

No source code commenting? No problem.

It crashes my browser

Awesome demo :-).

great stuff. nice job!

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