Dear Fellow Scholars, this is Two Minute Papers
with Dr. Károly Zsolnai-Fehér. Let’s talk about snow simulations! Being able to simulate snow on our computers
is not new, it’s been possible for a few years now, for instance, this legendary Disney
paper from 2013 was capable of performing that. So why do researchers write new papers on
this? Well, because the 2013 paper had its limitations. Let’s talk about them while looking at some
really sweet footage from a new paper. Limitation number one for previous works is
that their snow simulations were sinfully expensive. Most of them took not seconds, and sometimes
not even minutes, but half an hour per frame. Yes, that means all nighter simulations. They were also not as good in fracturing interactions,
simulating powder snow and avalanches were also out of reach. Until now. You see, simulating snow is quite challenging. It clumps up, deforms, breaks, and hardens
under compression. And even my favorite, phase change from fluid
to snow! These are all really challenging to simulate
properly, and in a moment, you will see that this new method is capable of even more beyond
that. Let’s start with friction. First, we turn on the snow machine. And then, engage the wipers! That looks wonderful. And now, may I request seeing some tire marks? There you go! This looks really good, so how about taking
a closer look at this phenomenon? Vb here is the boundary friction coefficient
and it is a parameter that can be chosen freely by us. So let’s see what that looks like! If we initialize this to a low value, we’ll
get very little friction, and if we crank this up, look, things get a great deal more
sticky. The big clump of snow also breaks apart in
a spectacular manner, also showcasing compression and fracturing beyond the boundary friction
effect we just looked at. Oh my! This is beautiful. Okay, now, this is a computer graphics paper. If you are a seasoned Fellow Scholar, you
know that this means…it means that it is time to put some virtual bunnies into the
oven. This is a great example for rule number one
for watching physics simulations, which is that we discuss the physics part, and not
the visuals. So why are these bunnies blue? Well, let’s chuck’em in the oven and find
out. Aha! They are color coded for temperature. Look, they start from -100C, that’s the
blue, and we see the colors change as they approach zero degrees celsius. At this point they don’t yet start melting,
but they are already falling apart, so it was indeed a good design decision to show
the temperatures, because it tells us exactly what is going on here. Without it, we would be expecting melting. Well, can we see that melting in action too? You bet. Now, hold on to your papers, and bring forth
the soft-ice-o-mat! This machine can not only create an exquisite
dessert for computer graphics researchers, but also showcases the individual contributions
of this new technique one by one. Look! There is the melting, yes! Add a little frosting, and there you go. Bon appetit! Now, as we feared, many of these larger-scale
simulations require computing the physics for millions of particles. So how long does that take? When we need millions of particles, we typically
have to wait a few minutes per frame, but if we have a smaller scene, we can get away
with these computations in a few seconds per frame! Goodness, we went from hours per frame to
seconds per frame in just one paper. Outstanding work. And also, wait a second…if we are talking
millions of particles, I wonder how much memory it takes to keep track of them? Let’s see. Whoa…this is very appealing. I was expecting a few gigabytes, yet it only
asks for a fraction of it…a couple hundred megabytes. So, with this hefty value proposition, it
is no wonder that this paper has been accepted to the SIGGRAPH conference. This is the olympic gold medal of computer
graphics research, if you will. Huge congratulations to the authors of
this paper… this was quite an experience. What a time to be alive! Thanks for watching and for your generous
support, and I'll see you next time!
