
Mathematicians bring ocean to life for Disney's 'Moana' - oscarwao
https://phys.org/news/2017-01-mathematicians-ocean-life-disney-moana.html
======
aidos
We watched Monana a couple of weeks ago and afterwards my wife said that she
was amazed with how good the water looked. I said, I bet there were a bunch of
mathematicians working on that :-)

In another life I'd be doing maths for 3D movies. I went to university in
Wellington where Weta are based (Peter Jackson's film companies) and at one
point had a look around the digital arm. I seem to recall that they had the
SGI machines as desktops and a big unix rendering farm. I just love the way
you can use maths to create such magic.

Anyway, if you haven't seen it yet, Moana is fantastic. Incredible animation,
catchy pop hooks in the music and a brilliant storyline. It's wonderful to see
a Disney film with a strong female lead that needs neither male support nor a
love interest.

~~~
ashark
> a strong female lead that needs neither male support nor a love interest

Now I'm trying to think of other Disney leads of _either_ sex without a love
interest... is there one? Other than those for whom it's not really applicable
(ones who are too young, mostly).

~~~
JustinGarrison
Judy (Zootopia) Hiro (Big Hero 6) Elsa (Frozen) Ralph and Velellope (Wreck it
Ralph)

There are plenty more. I think it has more been current society that is
recognizing it more.

~~~
pjc50
_Wreck it Ralph_ puts the love interest relationship between Felix and Calhoun
(and subverts it all over the place).

Those are all quite recent, while the historical Disney films all fall into
the traditional template of male and female lead falling for each other. To
the extent that _Enchanted_ can assume the audience knows the formula that
they're parodying.

There is indeed a recognition and a policy change that stories don't have to
be made to fit that formula any more. And it seems that the films are
exploring other affectionate relationships, such as the sisters in _Frozen_.
_Wreck it Ralph_ clearly has _affection_ between Ralph and Vanellope, but it's
more a parental/big-brother-little-sister thing than a romance. _Brave_
focuses on mother/daughter. And so on.

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Animats
"Solve, or nearly solve, partial differential equations". That's game physics.
Most of the effort is to come up with ways to "nearly solve" without having
awful stuff happen. There's a long history of awful stuff, going back to when
Seamus Blackley botched Trespasser in 1998.

Game physics still tends to go "boink", because with impulse/constraint
collisions, everything, including large, heavy objects, bounces
instantaneously. Stuff flying apart, though, is rare now; most systems drain
the energy out of a system when they detect that happening. It's physically
wrong, but looks less awful.

I used to work on this stuff. I solved the "boink" problem for articulated
rigid body physics in the 1990s, but couldn't make it work in real time on
100MHz CPUs.

~~~
santaclaus
> Stuff flying apart, though, is rare now; most systems drain the energy out
> of a system when they detect that happening. It's physically wrong, but
> looks less awful.

Most games are using position based dynamics now (see Nvidia PhysX) so there
isn't even a variational principle to arrive at the system from an energy.
Just a constraint satisfaction problem with a weak notion of momentum coupled
in.

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NiceGuy_Ty
Also coming into play during Moana is the hyperion rendering engine, which was
first showcased in Big Hero 6:

[https://www.disneyanimation.com/technology/innovations/hyper...](https://www.disneyanimation.com/technology/innovations/hyperion)

Also, here's an article containing some stills from the movie:

[http://blog.yiningkarlli.com/2016/11/moana.html](http://blog.yiningkarlli.com/2016/11/moana.html)

~~~
joering2
Thank for sharing - never been on DA website.

The whole blog of publications is super interesting!

[https://www.disneyanimation.com/technology/publications](https://www.disneyanimation.com/technology/publications)

~~~
JustinGarrison
Glad you like it. I work at Disney Animation. I have been pushing to get more
"Innovations" posted but it's not always the easiest thing to get "secret
sauce" published.
[https://www.disneyanimation.com/technology/innovations](https://www.disneyanimation.com/technology/innovations)

I also helped push this forward to get other divisions to think about open
sourcing code more often. [http://disney.github.io/](http://disney.github.io/)

------
avenoir
I was looking at the animation referenced in the article of water flowing over
a rocky terrain and couldn't help but notice almost life-like and pixel-
perfect precision of collision detection between water particles and the rocky
surface. Yet, in modern gaming, while it's improved a great deal, quite often
you'll see surfaces "fusing" together before a collision is detected. I think
there is a more technical term for this, but it's not coming to mind. Is this
just a matter of usability vs performance?

~~~
SomeStupidPoint
The movie is using a whole compute cluster to do a physics simulation when
rendering the movie. Your computer has 1 CPU and 1 GPU.

Your computer is just very limited in how much attention to detail it can
have, because it has wildly less processing power _and_ has to get its job
done in real time.

By contrast, Disney is using a server farm to spend 3 seconds analyzing the
mechanics of a tuft of hair wiggling in the breeze for 1 second.

~~~
tarr11
Has anyone tried to make a real game in the same way?

Ie a game which was hosted on a remote desktop that had direct access to a GPU
server farm on a very fast network.

~~~
aidos
Not a field I work in but I guess it would never work. You'll have the network
latency to contend with. Or people would need to self host a server farm,
which probably makes your market pretty small :-)

~~~
TeMPOraL
I wouldn't say never. The golden rule of computer games code is that you get
to cheat _a lot_.

------
Fricken
I've been waiting decades to play a surf sim that utilizes proper fluid
dynamics. Maybe before I die it'll happen.

~~~
nether
Wave Race 64 had plausible wave physics. Could probably go much further with
the hardware of today.

------
jordache
Why is it that we can accept expressive/cartoonish looking characters but need
to have the most realistic environmental rendering (light, physics effects)?

I challenge the studios to be imaginative and equally expressive on the
latter. Give us the miyazaki equivalent in 3d animated films.

Don't take fthe easy way out by emulating reality. Put true art into it

~~~
alxndr
My guess is the uncanny valley[0] is still too big for "realistic" human
characters. As for the goofy-looking chicken, it's convenient to make an
animal goofy-looking for comic relief. (And in the case of Jiminy Cricket, I
think Disney would rather draw, and people would rather look at, a humanoid
with a weird head than an actual insect.)

[0] "the uncanny valley is the hypothesis that human replicas that appear
almost, but not exactly, like real human beings elicit feelings of eeriness
and revulsion among some observers"
[https://en.wikipedia.org/wiki/Uncanny_valley](https://en.wikipedia.org/wiki/Uncanny_valley)

------
baq
for the EU viewers that are confused: in some countries the title and the
character's name is Vaiana.

~~~
D_Guidi
moana pozzi was a famous italian porn actress in the '80, that made also
standard tv programs and involved in politics, too. I'm pretty sure she was
famous in Europe too.

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ufo
I wish the article went more into detail about what is novel about the
algorithms they worked on.

~~~
chestervonwinch
[https://www.math.ucla.edu/~jteran/papers/JSSTS15.pdf](https://www.math.ucla.edu/~jteran/papers/JSSTS15.pdf)

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santaclaus
The hair was also great in Moana. It is fun to see nonlinear Cosserst rod
theory in use on the big screen!

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speps
The Taichi library linked [1] on HN recently has a MIT licensed APIC
implementation here :

[https://github.com/IteratorAdvance/taichi/blob/master/includ...](https://github.com/IteratorAdvance/taichi/blob/master/include/taichi/dynamics/apic.cpp)

[1]:
[https://news.ycombinator.com/item?id=13325190](https://news.ycombinator.com/item?id=13325190)

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chis
This is really cool. I wonder how one goes about getting into work like this -
niche field but few qualified to work it, I'd guess.

~~~
batty
You can come do a PhD with me at Waterloo. #shamelessplug
[https://cs.uwaterloo.ca/~c2batty/](https://cs.uwaterloo.ca/~c2batty/)

~~~
chis
Small world! I actually am majoring in comp sci and physics. I'll definitely
message you if I end up getting into research next year.

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megablast
Scarily realistic:
[https://www.youtube.com/watch?v=3mULoRzfFcE](https://www.youtube.com/watch?v=3mULoRzfFcE)

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LeoPanthera
A little off-topic, but this site's cert appears to have a revoked
intermediate authority. Pic:
[http://i.imgur.com/lIseT66.png](http://i.imgur.com/lIseT66.png)

But no-one else seems to be complaining about this so I wonder if it's just
me?

~~~
Raticide
All fine for me in Safari on OSX 10.10.3
[http://i.imgur.com/ZwbQ08N.png](http://i.imgur.com/ZwbQ08N.png)

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a_c
In the video, it is mentioned several times "stability" and "noise". Can
someone explain what do these two terms refer to in the sense of particle
simulation?

------
supergirl
"where they used science to animate snow scenes"

Cringes

~~~
izym
Well, they did, in a very non-buzzwordy manner.

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amelius
This is nice from an artistic perspective. But from a computational physics
perspective, it feels like cheating. How much of this is realistic? And are we
now encouraging more and more people to focus on "fake" physics because it
makes it somehow easier to produce something cool? I sure hope not.

~~~
deburo
It's not all about looking cool, it's about coming up with algorithms that are
computable in a reasonable amount of time while also behaving as similarly as
it is possible to interactions of objects in the real world.

Faking physics is a mastery. Trade-offs are unavoidable.

