Dear Fellow Scholars, this is Two Minute Papers with Dr. Károly Zsolnai-Fehér.
It’s time for some fluid simulations again! Writing fluid simulations is one of the most
fun things we can do within computer graphics, because we can create a virtual scene, add
the laws of physics for fluid motion, and create photorealistic footage with an absolutely
incredible amount of detail and realism. Note that we can do this ourselves, so much so,
that for this scene, I ran the fluid and light simulation myself here at the Two Minute Papers
studio, and, on consumer hardware.
However, despite this amazing looking footage, we are not nearly done yet! There is still
so much to explore! For instance, a big challenge these days is trying to simulate fluid-solid
interactions. This means that the sand is allowed to have an effect on the fluid, but
at the same time, as the fluid sloshes around, it also moves the sand particles within. This
is what we refer to as two-way coupling.
We also know that there are different kinds of two-way coupling, and only the more advanced
ones can correctly simulate how real honey supports the dipper and there is barely any
movement. This may be about the only place on the internet where we are super happy that
nothing at all is happening.
However, many of you astute Fellow Scholars immediately ask, okay, but what kind of honey
are we talking about? We can buy tens, if not hundreds of different kinds of honey at
the market. If we don’t know what kind of honey we are using, how do we know if this
simulation is too viscous, or not viscous enough? Great question!
Just to make sure we don’t get lost, viscosity means the amount of resistance against deformation,
therefore, as we go up, you can witness this kind of resistance increasing. And now, hold
on to your papers because this new technique comes from the same authors as the previous
one with the honey dipper, and enables us to import our real-world honey into our simulation.
That sounds like science fiction. Importing real-world materials into a computer simulation?
How is that even possible? Well, with this solution, all we need to do is point a consumer
smartphone camera at the phenomenon and record it. The proposed technique does all the heavy
lifting by first, extracting the silhouette of the footage, and then, creating a simulation
that tries to reproduce this behavior. The closer it is, the better. However, at first,
of course, we don’t know the exact parameters that would result in this, however, now we
have an objective we can work towards. The goal is to re-run this simulation with different
parameter sets, in a way to minimize the difference between the simulation and reality. This is
not just working by trial and error but through a technique that we refer to as mathematical
optimization.
As you see, later, the technique was able to successfully identify the appropriate viscosity
parameter. And when evaluating these results, note that this work does not deal with how
things look - for instance, whether the honey has the proper color or translucency is not
the point here. What we are trying to reproduce is not how it looks, but how it moves.
It works on a variety of different fluid types. I have slowed down some of these videos to
make sure we can appreciate together how amazingly good these estimations are.
And we’re not even done yet! If we wish to, we can even set up a similar scene as
the real-world one with our simulation as a proxy for the real honey or caramel flow.
After that, we can perform anything we want with this virtual piece of fluid, even including
putting it into novel scenarios, like this scene which would otherwise be difficult to
control, and quite wasteful, or even creating the perfect honey dipper experiment. Look
at how perfect the symmetry is there down below! Yum! Normally, in a real-world environment,
we cannot pour the honey and apply forces this accurately, but in a simulation, we can
do anything we want! And now, we can also import the exact kind of materials from our
real world repertoire. If you can buy it, you can simulate it. What a time to be alive!
This episode has been supported by Linode. Linode is the world’s largest independent
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this while I was working on my last few papers! To receive $20 in credit on your new Linode
account, visit linode.com/papers or click the link in the description and give it a
try today! Our thanks to Linode for supporting the series and helping us make better videos
for you.
Thanks for watching and for your generous support, and I'll see you next time!