Sunday, June 8, 2008

Animation Ramble - Appealing ARCs = Happy Animator

I want to talk about a trend I have observed among some students in my time as a teacher. Its something that can happen when you start moving beyond basic exercises and venture into more complicated scenarios.

There is a special secret that you need to remember about the fundamental animation principles as you start animating more complex situations and it goes a little something like this. . . . The fundamentals are FUNDAMENTAL, you can't change em, amend them or ignore them because of a specific situation. They are called fundamental because they apply to 99.9% of the animation you will ever make.

Lets look at some different kinds of jumps here to explain what I mean......

Click the image to watch at or click HERE to download your own copy.

OK so the first clip is our base line, or standard. The little girl doesnt do much in the air, just tucks her legs up. The jumpers height eases in to the peak of the arc (decelerating) and then eases out from the peak (accelerating). With the possible exception of some further forward momentum from the man holding the jumpers hand its the standard arc we should all be familiar with from our very first bouncing ball exercise. Appealing and easy right?

So lets look at some more complicated things. Next up I want to look at some ballet. Ballet is really good for live action refference because it is all about control. The performer (a good performer) is as concerned with their form and movement as they are how high or hard they jump, if you want broad, cool, controlled, and slick looking movement then this is an excelent place to start. You may not want all of your characters to look like they are prancing around in a field of daisys, but remember we are looking at Fundamentals here, you can always tweek the poses to suit your own needs. As a refference point for the over all movement and arcs through the body you needn't go any further than a good ballet performance.I imported the clips into Flash so I could draw over the top of the video, I'll put some technical notes at the end on how to do this for anyone who wants to have a go at this sort of thing themselves. I found it quite educational myself.
You can see from this trace over of the first jump that there is quite a lot going on, especially in the legs. He dose a kind of double scissor kick and they are flinging back and forth quickly while his upper body maintains an serine flowing arc. Next I went over the same frames and drew a kind of blob over what I figured were the heavier parts of his body (from the head down to the pelvis). You can see we pretty much still have the basic bouncing ball shape in the arc. There are no suden changes in direction. There may be some slight variations in his forward movement created by the leg swinging, but they are very subtle, you definately wouldn't start by animating them in, they would be added in later. On the whole we have the same basic and appealing underlying movement.

Next lets look at something where the changes taking place in the air are even more dramatic. Someone doing a flying side kick into a punching bag.Some great action poses in this clip. Again I traced over a series of frames.The whole body is twisting sideways in the air, he flings his legs out in front of him, and then there is his impact with the punching bag. All important elemants within the scene, but the fundamental rule still wins out in the end.The blob test still reviels an appealing arc. Even his impact with the puching bag about 5 frames from the end of the section I have traced over here can't through him completly off his arc. It slows his forward momentum, but does not result in a sunden change of direction or total disruption of the arc. His leg and the object he is kicking absorb their fair share of the energy. It may have been a slightly different case if he hit a force comming back at him in the oposite direction, but I think it is still quite a striking demonstration of just how hard it is to through a large object flying through the air off its arc. I think we would all agree he kicks that bag pretty hard, but the arc continues with only a slight amendment to its path
Another great thing you can do when breaking down a live action scene this way is to track some of the more specific arc in the movement. As you can see here I found the fact that there were clear relationships between the arcs on different parts of the body, when I probably have a tendancy to think about them individually when I animate. I wonder if that relationship helps to keep the movement more appealing?

So we have broken down two situations where the character is in control, but what about when your character looses control? In this case the jumper starts with the best of intentions, but then changes his mind half way through the jump. I have to warn you that when I searched for this clip on youtube I found some truely hidious trampoline accidents, if your squeemish, be careful when searching.As I traced this one I moved each frame over a set amount to spread the action out so we can see it clearly. Things are looking OK up to about the 3rd frame, but then instead of tucking his legs up his body says no and stiffens out flat in the air. The problem with this "plan" is that while you can have quite a strong infuence on the rotation of your body in the air by flinging your arms, legs and head around, there isn't much you can do about the momentum you created as you were leaving the ground. Powerful forces are set in motion that can't be changed unless a second more powerfull force is applied, and I'm afraid flinging your limbs about is no match for the force you creat through phisical contact with a solid object like the ground. The result is that he may have slowed his rotation (probably making things worse), but he couldn't help but continue over, the weight of his head would almost definately counteracted any influence from him straightening his body. Ouch! I hope he wan't seriously hurt.

You can see in our blob breakdown that the same rules apply, and appealing sence of up and down.

Can you see what I'm getting at. What I'm trying to say is that in 99% of cases there is no excuse for disreguarding the basics. Its tricky I admit, but as you move into more complicated scenes you need to multi task, introducing the more complex elements but still stay true the the laws of physics. We talk a lot about appeal in our classes, but I think for many its just about a character design or single frame, but as an animator you are responsible for creating appealing movement .

This can be even harder in 3D animation, you character often progresses through the air as a conciquence of animation on a object outside of the body and overlaps with movement on individual elements within the rig. You have to keep your animator hat on, look at the overall poses and get them where you know they should be.

The last clip is just for further refference, watch all the different shapes he twists himselves into in the air, but always following the Fandamental rule and creating appealing arcs through the air.

Technical stuff:

  • To trace over these clips I fist downloaded the clips from Youtube. There are lots of free programs for doing this, I use this one.
  • Next I import the video into Flash - File>Import>Import Video.... You have to go through a few pages of options to import, the only one you need to change from the default is on the second page called "Deployment" and you have to choose, "Embed video in SWF and play in timeline"
  • So the video should open in a new layer on your timeline, now you can ad new layers and draw over the top of the video frames.
  • MOVING CAMERAS? - Many youtube clips are filmed with hand held video cameras that make it hard to use the video for reference, As long as the action is all in frame and there are object in the background not moving I have a work around for this. Pick a stationary element in the background that doesn't get obscured by the character too much. On a new layer (lets call it REF) put a dot on part of this object that is clearly visible. Before you move on to trace a new frame, grab the video layer and move it so that the object in the background stays in line with the mark on the REF layer. This locks the background down in the same place each time, effectively taking out the camera movement and leaving you with a pretty accurate recreation of the characters movement. In the flying side kick example I put a dot on the corners of the red mat against the back wall and used them to keep the background stationary.
  • Remember what Milt Karl said in the recent Youtube clip I posted about him, the point of live action reference is to use it to understand the action to a point that you don't need the live action reference any more. Just turning your brain off and tracing is not much help to you. :)

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