Wednesday, March 19, 2014

The Secret Behind the "Frozen" Animation

Wow, Isn't That Realistic? Here's Why

"Frozen" (2013).
This is a blog about animation, so sometimes we peel back the curtain and get into the nitty-gritty just a tiny bit. This is one of those times, so this post may only be of interest to fellow geeks. But all fans of animation may enjoy understanding what they are seeing on screen without having to get too technical. As an added bonus, you can sound knowledgeable when casually discussing animated films with your friends.

The Disney smash-hit animated feature film "Frozen" is set in the snowy north of Norway and has a fresh, unique visual look to it. No other animated feature film has ever created snowy vistas as accurately as "Frozen," and there is a very simple reason why: animators never had the proper technology before or did not know where to look for it. Well, now they do.

It is easy to say "well, everything is computer graphics now, and they can pretty much show anything they want to on the screen." That is true up to a point, but CGI in its basic form only takes you so far. CGI requires specialization after that to get just the right look in dynamic situations.

Case in point: the snow and ice effects in "Frozen." Researchers at the University of Missouri developed the Material Point Method (MPM) a computer-generated tool that creates blast scenarios that inform blast and impact-resistant materials and design. They used a $400,000, five-year CAREER grant from the National Science Foundation to create this method. While it wasn't designed for Hollywood, the folks at Disney perked up their heads when they saw what it could do.

Zhen Chen, C.W. LaPierre Professor of civil and environmental engineering at the College of Engineering at the University of Missouri, explains:
 "Motivated by the need for better simulations that demonstrate impact and penetration phenomena, we developed the MPM more than 20 years ago. Since then, the MPM has been further developed and applied by many global research teams to real-world problems including fire, explosions and impacts in buildings and structures. Our first study on the MPM has been cited more than 400 times, and Disney is now using physics-based simulation methods as they create sequences for their popular animated movies including 'Frozen.'"
Dr. Zhen Chen Frozen material point method animation
Dr. Zhen Chen.
The Disney animators used the MPM to develop snow simulations that mimicked snowball drops and smashes. They also animated the effects of characters walking through snowy backdrops. Since the entire film is of characters walking through snow, that means the MPM got a whole lot of use in "Frozen."

It's great that the singers and voice actors and directors get all the credit for an animated feature film's quality and success. Without taking a thing away from their contributions, the actors and so forth know where the true source of their success lies and no doubt wish that the grunts behind the scenes could also get their proper due. They never do, but that's how Hollywood works and everybody accepts that.

But to be fair, don't forget that those animators and creative types are building upon the hard work and brilliance of unknown and unsung heroes like Dr. Chen. I am only too happy to give him, his team, and others like him just a smidgen of the enormous credit that they so richly deserve for the entertainment we see at the theater and on tv. These guys are only going to get more important as the animation continues taking over Hollywood.

Here comes the heavy stuff!
For those really interested: MPM is an application of the Particle-in-cell (PIC) Method in computational fluid dynamics to computational solid dynamics. It is a Finite element method (FEM)-based particle method and is an alternative to dynamic FEM. Want a multiphase simulation to show large-object deformations? You use MPM.

MPM moves Lagrangian point masses, or material points, against a Eulerian background mesh. "convective steps" occur, with the mesh reset to its original position, while the material points remain where they were. FEM and MPM can be combined together for large-scale simulations.

I know that is heavy stuff. But that is what is required by today's cutting edge animation. It is very complex and not something that was available in the past.


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