What causes 3D animated “bloopers”?

Question

I’m talking about things like [Merida’s eyes being all buggy when animating Brave](https://www.youtube.com/watch?v=4405qEhBmEM) or [everyone’s hair going in weird directions in The Incredibles](https://www.youtube.com/watch?v=Y_MQnH54XaA) or [Shrek’s arms suddenly getting really long](https://www.youtube.com/watch?v=UNngNiYXuVE). Why does the animation fail in (apparently) random and uncontrollable ways?

In: Technology

Answer 1

I haven’t done much 3D animation, but I do dabble in game development, and there’s a decent bit of overlap in how those two fields tend to work.

So basically in modern games and 3D movies, there’s way too much stuff going on for actual people to be arranging every single thing in every single frame, so what we do is create systems where the people set up the ‘broad strokes’ of what is supposed to happen, and then computer programs take that info and figure out all of the details and the in-between steps.

As an example, I was recently setting up a player character in a video game, and I had three animations for that character, an idle (standing still) animation, a slow walk animation, and a full-speed run animation. But depending on how the player wants to move, their character doesn’t just travel at those three different speeds. They can accelerate and decelerate at all of the speeds in between. So the game engine that I’m using contains functionality that lets me set up ‘animation blends’ between different animations, where once I’ve set it up, the computer will basically combine those three animations to create intermediate speed walks/runs as the player accelerates/decelerates.

And stuff like that is how tons of things in games and 3D animation work. Besides just blending animation, we’ve got programs that dynamically changes shapes/textures/whatever we need. Stuff like hair and fur is typically rendered using these sorts of programs. We’ve got physics engines that attempt to simulate things moving and colliding. There’s cloth simulations that can be used for things like clothing and flags. Weather systems that add in clouds/rain/lighting changes/etc.

And the ‘fun’ thing about all of these systems is that they’re often fairly complicated, and minor changes in how you’ve configured them can result in big changes in the output, and often in unpredictable and undesirable ways. And sometimes they just ‘freak out’ and super weird stuff like you see in those blooper trailers happens.