- Hi, I'm Rob Jensen, and I'm an animator. Before we talk about computer animation and algorithms and all that, let's just talk about what
animation is at it's core. All animation is based on the same idea. Making changes to a series of images and playing those images back in sequence. Now in hand-drawn animation,
we do this by drawing. Animators draw key poses and then draw a series of pictures
we call in-betweens that connect the motion
from one pose to another. It's a lot of drawing. In computer animation, we animate by moving virtual digital models. We call this posing. The poses we create are translated into coordinates that are
recorded on a spreadsheet. The computer fills in
the in-between images. These in-betweens are the result of a computer interpreting what motion would move an image from
this pose to that pose. Of course, the computer can't act, so it gives us this. We refine the in-betweens to turn this robotic motion into
a polished performance like this. And there are many different ways of filling in the in-betweens. But each can be described using a mathematical function called a spline. And this is where the
math meets the artistry. The simplest way to see this spline idea is through a bouncing ball. I'm going to make it
bounce from here to here with four main poses that I define by setting keyframes. The computer draws all the other frames by evaluating the spline. By default, the computer makes a linear interpolation of the motion and we get something that
moves at a constant speed. Hmm. Now from physics we know that the ball should accelerate on the way down and decelerate on the way up. I can adjust the shape of the spline to change the timing. Now we got something that
looks more realistic, but it's still pretty generic. As an animator, it's my job to bring to life a specific character. So I need to ask myself some questions. Is the ball heavy and depressed like this? Or maybe it's happy. Maybe it's a balloon. Once I answer these questions, I can choose what kind of spline I think will have that
effect in the motion. And this gets even more exciting when you're looking at a
character and their physics because how a character moves says a lot about who they are. For example, Mr. Incredible in this scene, the animation needs to show him lifting up a train car. Now, in animation, you can make that seem really quick and easy, but the director didn't want that. He wanted the audience to know that Mr. Incredible
could do amazing things but that it took a lot
of effort to do them. So, the way we define the speed of the in-betweens will make the difference between the train looking light or the train looking heavy. So, let's be clear. The computer helps us a lot, but ultimately this job
is really about acting. But instead of being in front of a camera, you're taking the performance and breaking it down into tiny little 24th of a second increments, and expressing those in an
abstract mathematical function. Pretty cool, right?