The Midnight Diaries of Catty Wampus

This is a technique I use in absolutely every shot I do, several times an hour at least. Sometimes I can spend minutes doing it. I don’t know how I ever lived without doing it.

The technique comes courtesy of Jeff Riley, a stop-motion animator currently working on Coraline, and whose film Operation: Fish making its way through the festival circuit. I know that Jeff didn’t come up with this, and it’s a technique that’s probably been used for decades and decades in other forms of animation. I’ve just never seen too many CG animators doing it. It goes like this:

When you move from one pose to the next, nearly every single body part should move, even if it’s only a little bit. And you need to make sure each part moves naturally. So, in order to check that each body part is moving the way that it should, you’ll have to rely on your “next key” and “previous key” buttons. Just check two keys, over and over, back and forth, back and forth, back and forth, back and forth. Watch each body part for its spacing–the amount each part moves from one frame to the next. Back and forth, back and forth. This is essentially what 2d artists do when they roll their drawings between their fingers, checking from one to the next. Stop-mo animators do it with their frame-grabbers. We have the “next key” and “previous key” buttons.

Let’s check out a simple example of what I’m talking about, shall we?

I’ve pulled a small clip from The Incredibles. This is from the scene where Mr. Huff is threatening to fire Bob. This is how the scene plays out in real time:

There are some great things going on with Huff, and I encourage you to frame through his motion. But for this example, we’re going to focus on Bob.

You can see that Bob pretty much has two poses: 1) Fuming with both arms at his side, and 2) Fuming with one arm extended outward, holding Huff by the neck.

From that description, it sounds like the only thing that changes is the screen left arm. However, if we just look at those two key poses, using the back and forth technique, we can see subtler changes as well:

You can see that when Bob’s arm goes up, his shoulder goes up, too. But that’s just the start. Look at the other changes:

1) The hips shift towards screen left just a little bit. Even though it’s a small change, it sells the idea of the body’s inertia.
2) The screen right shoulder also moves up quite a bit.
3) The screen right arm pulls in closer to the body.
4) The screen right hand clenches into a tighter fist and rotates up towards the body.
5) The head changes its angle slightly: rotating in the direction of the pose, and tilting downwards
6) The face clenches tighter and the eyes pinch shut

Every single part of Bob’s body has moved, even though the major change is only that one extended arm. And the best way to see the changes in each body part is, say it with me: back and forth.

You can use this back and forth method to check out how each part of your character moves from one key to the next, making little adjustments where you need to and then checking them again using back and forth, back and forth, back and forth. This is what is meant when you hear people say they are “checking out how two frames animate”–they’re watching all of the differences between the two keys, large and small, to make sure that the movement makes sense.

Let’s check out an even more dramatic example. This one is from Aladdin, during the song “One Jump Ahead.” Again, to start, we have the clip in real time:

Got it? Good.

Once again, it looks like there are only two major poses going on here: 1) Leaning out from the post, and 2) Hiding behind the post. We can go back and forth and check out those two poses:

Clearly, these two keys have much bigger spacing from the first clip we watched from The Incredibles. If you were animating this scene, you might be satisfied with these two poses, confident that they’re selling the ideas in the scene that you want to get across to the audience. So, where do you move from there? You put in breakdowns. Here’s how back and forth can help.

These are the breakdowns that are in the scene:

Note: I don’t know for certain which are the exact keys and breakdowns the animator chose. I’m making my best educated guess.

You can see how nicely they work with each other. Everything is moving on nice arcs, each body part feels natural. But we’re looking at this after the fact. If you were animating this scene, you’d have to do a lot of back and forth checking to make sure that each of your breakdowns are working properly. So for the first set of breakdowns, you might find yourself looking at your keys something like this:

You’d go back and forth, over and over, forwards and backwards, over and over, just to make sure everything is working with each other. These are just the first keys and breakdowns:

Frame 1 - Leaning out from the post
Frame 32 - Leaning out further (to accentuate the song lyric)
Frame 49 - Pulling backwards to escape the flying swords and spears

Then, once you were satisfied with how those frames were working together, you might check on your next breakdown or two:

Over and over, back and forth, forwards and backwards. Over and over. From one key to the next, over and over, forwards and backwards, back and forth.

If I’m coming across as repetitive, that’s part of the point. Remember, from an earlier post when I wrote about how Every Frame Is A Drawing? Well, I use back and forth every single time I make a new drawing. My “next key” and “previous key” buttons are some of the most used keys on my keyboard. It’s the best way I know to check how your keys are working before you put in your breakdowns. And then, you can check how your breakdowns are working before you put in your inbetweens.

Back and forth is all about keeping iron-clad control over your animation, and not letting the computer put in any motion that you don’t want there.

Good luck, and happy animating!