What is flow?
Flow, or fluidity, is keeping your animations moving constantly without changing the momentum. It’s avoiding unnecessary stoppages and making everything move smoothly and pleasantly. It makes an animation look better because when an animation is flowing the eye is instinctively looking at where it expects the animation to be next, and the less work you make a viewer’s eyes do the better.
Take a look at some examples:
This animation flows. The movement never stops and all the momentum is carried on. He changes direction a few times but it is always guided around in such a way as to let everything keep going. I’ll show you how to do this better later.
This animation mostly flows. When I started making it I wanted it to be my primary example, but I made a mistake and decided it would be easier to highlight the mistake than fix it. If you look closely you’ll see that he speeds up after the first handspring and then slows down again when he hits the ground. This is bad flow, because the speed changes unnecessarily.
This does not flow. There are sudden changes of direction and some things aren’t moving some of the time. Momentum is lost with no real cause. Worst of all, there is shakiness. Shakiness instantly destroys flow. If you are aiming for flow there cannot be a single frame that goes back on itself.
So how do I do it?
For most movements it will be the natural state of things. Look at this walk:
There’s nothing special about it beyond the fact that I made it (which instantly makes it awesome) but it all flows. If it didn’t flow it would not be an accurate representation of a walk. Some people’s walks do not flow, however. If you do one step at a time like this:
then you are not flowing properly. Sweet Jesus fuck, that's awful. Originally I had an awesome example here which was made by Cronos. It was perfect in every respect apart from flow. Then the link broke and this was the only suitable example I could find. I mean, holy shit. Just, like, imagine that the flow is the only problem. I'll try to get a better example up ASAP. (This note left 04/12/13. British dates - that's not an April thing. Anyway, if it's now 2015 or something then I guess I forgot. I'm sorry about that.)
The steps need to merge into one another. The point is, when you’re doing more than one movement the end of the last movement needs to be the start of the next. See how in my first example the front foot is already moving backwards when it hits the floor? That’s because in the next movement – the next step – that’s the direction that that foot is going to be moving. At the back of the stride the foot keeps going backwards for a moment after lifting off. Same principle. If it takes it one step at a time and moves forwards, back, forwards, back, then that’s precisely what he’s doing. He takes a step. He takes another step. No one moves like that.
Apply the same principle to this animation:
Watch the hand from the first punch. It doesn’t stop moving after the punch, but goes straight back around into the reaction hand for the strike. Watch the hand that doesn’t punch. After moving back as reaction for the punch it curves around without stopping into the strike. No pauses – fluid movement.
As opposed to this one:
In which he stops his hands after the first punch before the second one starts.
Circles
“But I want to change direction!” I hear you cry. Fear not, dear fellow. Nature hath provided us a means to get around the problem without the need to stop. You see, rather than moving from left to right and then back again like this:
We are going to be moving from left to right and then easing out of the horizontal motion straight into vertical motion[/I] and then around further into the horizontal motion the opposite way, like this:
See? The speed is never reduced – just redirected. If we were to track the middle of the balls along the bottom we would see that the horizontal easing is more or less the same for both. The only difference is the height.
That doesn’t look so impressive just with circles, so here it is when you give the circles legs:
See? Constant movement.
Multiple jumps
Jumping with flow is a funny one, because you have to have enough time on the floor to do the jump, and also not so much time on the floor that you seem to slow down and lose momentum. Mostly this is how to do it (minus the small handspring issue mentioned earlier):
The trick is to hit the ground at an angle rather than horizontally, so that you can absorb the impact and bend the knees whilst the body is getting itself vertical and then extend as it goes past. Here’s an example of what I mean slowed down and zoomed in:
Think of it like going into a roll. When you go to roll you hit the ground at an angle and then leave at an angle:
That’s what you have to do when jumping, just upside down and back to front.
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I hope you’ve found this tutorial helpful. If there is anything more you would like to know on the subject, feel free to either PM me or leave a comment. Feel free to PM me or leave a comment anyway. I always like a good PM.
Also recommended: http://www.youtube.com/watch?v=ylCLIKKCGC8 - the first half at least is a good illustration of flow.
I have a feeling I've missed something huge and glaringly obvious. Can anyone see anything I could go into more detail with or anything?