4 ms·

Surface-Only Liquids

mizzao 10y ago
That looks pretty @%(*ing compelling. Does anyone know how novel this is, and whether it would be computationally feasible to implement in real time (e.g. video games?) I could already see it being very useful in for offline 3D animation, such as animated movies.
- jszymborski 10y ago
  Reminds of the work Ken Brakke has done with his Surface Evolver [0]. It's ancient, and it parses files written in it's own weird ini-like language [1] (seriously!?). If only it exposed a decent API (which would lend itself to e.g a python wrapper), it'd be the easiest thing on earth to use. [0] http://facstaff.susqu.edu/brakke/evolver/evolver.html http://facstaff.susqu.edu/brakke/evolver/evolver.html [1] http://facstaff.susqu.edu/brakke/evolver/html/datafile.htm http://facstaff.susqu.edu/brakke/evolver/html/datafile.htm
  - batty 10y ago
    Yes, there is a fair amount of similarly and connection in the underlying mesh data structure. In fact, we published a paper on that aspect of the framework at SIGGRAPH a couple years back, which heavily cites the Surface Evolver work. http://www.cs.columbia.edu/cg/multitracker/ http://www.cs.columbia.edu/cg/multitracker/
- bhouston 10y ago
  It is novel as it is an accepted paper to SIGGRAPH, generally considered to be the top computer graphics conference. I've pinged Christopher Batty, one of the co-authors, to come here and answer questions. :) Dr. Batty does have experience with offline 3D fluid simulators for movies: https://cs.uwaterloo.ca/~c2batty/ https://cs.uwaterloo.ca/~c2batty/
- batty 10y ago
  Thanks! At this point, since this is really the first version of a new and different technique than is typical in graphics, the method is not near real-time. As you suggest, the offline setting is probably the most relevant for now. We are hopeful that future research may substantially accelerate it.
davesque 10y ago
I definitely have no expertise and don't know how this fits into the larger field of research but the video's really fun to watch :).
- wlesieutre 10y ago
  SIGGRAPH videos are always a lot of fun. Two of my favorites: Rendering Synthetic Objects into Legacy Photographs https://vimeo.com/28962540 https://vimeo.com/28962540 Disney's Frozen A Material Point Method For Snow Simulation https://www.youtube.com/watch?v=O0kyDKu8K-k https://www.youtube.com/watch?v=O0kyDKu8K-k
asadlionpk 10y ago
Wow. Some years ago, I spent significant time on simulating 2d fluid for games. Here is one version of it: http://jsexperiments.herokuapp.com/sph/ http://jsexperiments.herokuapp.com/sph/ Ofcourse, this is completely different beast.
defenestration 10y ago
Wow, the demo in the YouTube video looks impressive. I would like to understand the technique they propose and what's unique in their thinking. Can someone with expertise on this topic explain the abstract in layman's terms? Abstract: We propose a novel surface-only technique for simulating incompressible, inviscid and uniform-density liquids with surface tension in three dimensions. The liquid surface is captured by a triangle mesh on which a Lagrangian velocity field is stored. Because advection of the velocity field may violate the incompressibility condition, we devise an orthogonal projection technique to remove the divergence while requiring the evaluation of only two boundary integrals. The forces of surface tension, gravity, and solid contact are all treated by a boundary element solve, allowing us to perform detailed simulations of a wide range of liquid phenomena, including waterbells, droplet and jet collisions, fluid chains, and crown splashes.
- santaclaus 10y ago
  Roughly, usually when simulating a fluid you have to consider the interior. Think of this as roughly scaling cubically in three dimensions. In this paper, they make some simplifying assumptions about the internal dynamics of a fluid that allows them to simulate with only a representation of the surface, which is lower dimensional and which will perform better (quadratic scaling under mesh refinement).
  - defenestration 10y ago
    Thanks, that makes sense. So, by describing a fluid as a surface instead of a volume you'll need less calculations to simulate the fluid and you'll gain performance. Let's dive into the details of the abstract. Please correct where wrong! '... for simulating incompressible, inviscid and uniform-density liquids with surface tension in three dimensions.' So it only works when you can't compress the fluid, the fluid is not sticky like honey or oil, had as uniform-density, and is an enclosed body (bubbles, not seas). 'The liquid surface is captured by a triangle mesh on which a Lagrangian velocity field is stored.' There seems to be two ways of looking at fluid motion. The Lagrangian way is following an individual parcel through time and space. The Eulerian way is looking at a specific location and watch fluid flow through that location. 'Because advection of the velocity field may violate the incompressibility condition,' Advection is the transport of a property by the fluid due to the fluids bulk motion. So the speed of fluid might compress the fluid, and that should be prevented. '... we devise an orthogonal projection technique to remove the divergence while requiring the evaluation of only two boundary integrals.' Orthogonal projection is representing a 3D object in two dimensions. In two dimensions there can be no divergence if I understand it correctly. 'The forces of surface tension, gravity, and solid contact are all treated by a boundary element solve, allowing us to perform detailed simulations of a wide range of liquid phenomena, including waterbells, droplet and jet collisions, fluid chains, and crown splashes.' The mathematics of surface tension, gravity and solid contact are much easier in two dimensions than in three. The boundary element solve is an efficient method to solve equations with boundery integrals. So liquid behavior can be modelled in more detail and visualized in a realistic way.

That looks pretty @%(*ing compelling. Does anyone know how novel this is, and whether it would be computationally feasible to implement in real time (e.g. video games?) I could already see it being very useful in for offline 3D animation, such as animated movies.

jszymborski 10y ago
Reminds of the work Ken Brakke has done with his Surface Evolver [0]. It's ancient, and it parses files written in it's own weird ini-like language [1] (seriously!?). If only it exposed a decent API (which would lend itself to e.g a python wrapper), it'd be the easiest thing on earth to use. [0] http://facstaff.susqu.edu/brakke/evolver/evolver.html http://facstaff.susqu.edu/brakke/evolver/evolver.html [1] http://facstaff.susqu.edu/brakke/evolver/html/datafile.htm http://facstaff.susqu.edu/brakke/evolver/html/datafile.htm
- batty 10y ago
  Yes, there is a fair amount of similarly and connection in the underlying mesh data structure. In fact, we published a paper on that aspect of the framework at SIGGRAPH a couple years back, which heavily cites the Surface Evolver work. http://www.cs.columbia.edu/cg/multitracker/ http://www.cs.columbia.edu/cg/multitracker/
bhouston 10y ago
It is novel as it is an accepted paper to SIGGRAPH, generally considered to be the top computer graphics conference. I've pinged Christopher Batty, one of the co-authors, to come here and answer questions. :) Dr. Batty does have experience with offline 3D fluid simulators for movies: https://cs.uwaterloo.ca/~c2batty/ https://cs.uwaterloo.ca/~c2batty/
batty 10y ago
Thanks! At this point, since this is really the first version of a new and different technique than is typical in graphics, the method is not near real-time. As you suggest, the offline setting is probably the most relevant for now. We are hopeful that future research may substantially accelerate it.

davesque 10y ago

I definitely have no expertise and don't know how this fits into the larger field of research but the video's really fun to watch :).

wlesieutre 10y ago
SIGGRAPH videos are always a lot of fun. Two of my favorites: Rendering Synthetic Objects into Legacy Photographs https://vimeo.com/28962540 https://vimeo.com/28962540 Disney's Frozen A Material Point Method For Snow Simulation https://www.youtube.com/watch?v=O0kyDKu8K-k https://www.youtube.com/watch?v=O0kyDKu8K-k

asadlionpk 10y ago

Wow. Some years ago, I spent significant time on simulating 2d fluid for games. Here is one version of it: http://jsexperiments.herokuapp.com/sph/ http://jsexperiments.herokuapp.com/sph/ Ofcourse, this is completely different beast.

defenestration 10y ago

Wow, the demo in the YouTube video looks impressive. I would like to understand the technique they propose and what's unique in their thinking. Can someone with expertise on this topic explain the abstract in layman's terms? Abstract: We propose a novel surface-only technique for simulating incompressible, inviscid and uniform-density liquids with surface tension in three dimensions. The liquid surface is captured by a triangle mesh on which a Lagrangian velocity field is stored. Because advection of the velocity field may violate the incompressibility condition, we devise an orthogonal projection technique to remove the divergence while requiring the evaluation of only two boundary integrals. The forces of surface tension, gravity, and solid contact are all treated by a boundary element solve, allowing us to perform detailed simulations of a wide range of liquid phenomena, including waterbells, droplet and jet collisions, fluid chains, and crown splashes.

santaclaus 10y ago
Roughly, usually when simulating a fluid you have to consider the interior. Think of this as roughly scaling cubically in three dimensions. In this paper, they make some simplifying assumptions about the internal dynamics of a fluid that allows them to simulate with only a representation of the surface, which is lower dimensional and which will perform better (quadratic scaling under mesh refinement).
- defenestration 10y ago
  Thanks, that makes sense. So, by describing a fluid as a surface instead of a volume you'll need less calculations to simulate the fluid and you'll gain performance. Let's dive into the details of the abstract. Please correct where wrong! '... for simulating incompressible, inviscid and uniform-density liquids with surface tension in three dimensions.' So it only works when you can't compress the fluid, the fluid is not sticky like honey or oil, had as uniform-density, and is an enclosed body (bubbles, not seas). 'The liquid surface is captured by a triangle mesh on which a Lagrangian velocity field is stored.' There seems to be two ways of looking at fluid motion. The Lagrangian way is following an individual parcel through time and space. The Eulerian way is looking at a specific location and watch fluid flow through that location. 'Because advection of the velocity field may violate the incompressibility condition,' Advection is the transport of a property by the fluid due to the fluids bulk motion. So the speed of fluid might compress the fluid, and that should be prevented. '... we devise an orthogonal projection technique to remove the divergence while requiring the evaluation of only two boundary integrals.' Orthogonal projection is representing a 3D object in two dimensions. In two dimensions there can be no divergence if I understand it correctly. 'The forces of surface tension, gravity, and solid contact are all treated by a boundary element solve, allowing us to perform detailed simulations of a wide range of liquid phenomena, including waterbells, droplet and jet collisions, fluid chains, and crown splashes.' The mathematics of surface tension, gravity and solid contact are much easier in two dimensions than in three. The boundary element solve is an efficient method to solve equations with boundery integrals. So liquid behavior can be modelled in more detail and visualized in a realistic way.