Jumps - Overlapping action

>>Jumps overlapping action. So overlapping action is one of the principles of animation and what’s meant by overlapping action is any secondary motion that occurs in addition to the primary motion. So for example, if a character is jumping, then the primary motion would be the jump itself and then the motion of the arms and the head would be what I’d call active secondary motion, which is animated by the character, while there are also passive secondary motions such as the drag of the clothing, hair, so forth. Now the timing of the overlapping actions may or may not have timing that matches the primary motion. Passive overlapping actions, like follow-through and drag, they’re often synchronized with the primary motion and also sometimes active overlapping actions are also synchronized, especially if they are in support of the primary motion. A good example of that is swinging the arms in a jump. So the height of a jump is significantly higher if you swing your arms as you’re taking off. And the swinging of the arms has 2 related effects. As you’re swinging the arms upward, you actually exert more force on the ground and so you have a larger reaction force pushing you up. And then also once you takeoff because your arms are raised, your center of gravity is already higher up off the ground. Now the correct way to swing the arms when jumping is to swing them while the feet are still in contact with the ground. Let’s just look at a quick video of that. So this is the correct way of swinging the arms in a jump. Now the incorrect way to animate the arm swing in a jump would be to swing the arms late. Basically to be swinging the arms as the character has already left the ground. Let’s see what happens if you try to jump in this fashion. This is very unnatural and highly uncomfortable, so I strongly recommend that you try it yourself so that you can feel what it’s like. Now what happens is if you throw your arms upward after you’ve left the ground, that shift of the center of gravity is located in your body of the center of gravity shifts to a higher position in your body but the center of gravity is the same distance from the ground so basically that means that you throw your body downward. So your torso or your body will shift downward by the action of swinging the arms up. So again, in animation the correct timing of the arm swing in support of the jump is as the feet are on the ground. Now once someone who’s jumping, a characters jumping, is in the air, they often will move their arms and legs and here’s a video of long jumper and you’ll see once they are in the air they have some arm motion. And here we see much of that arm motion is to control the rotation of the body while it’s in the air in order to land with the correct orientation we’ll see more about this when we talk about somersaults and twists and other such motion. Now there’s also passive overlapping action, so any kind of motion of the hair, the clothing, with this horse the mane of the horse, the tail, the clothing of the rider and so forth. So these passive overlapping actions in a jump are affected by the weight gain and loss in the motion. So just to review how this works, if you have an object, and its either accelerating up or accelerating down, there’s going to be a variation in the weight. So whenever the acceleration is with gravity, so if you are say falling and gaining speed or if you’re rising and losing speed, so this is a deceleration if you will, then those 2 types of motion are with gravity. And so the weight of, the effect of weight actually, goes down. On the other hand, if the motion is against gravity, so if it’s rising and speeding up or falling and slowing down, then there’s an effective gain in the weight and this is seen in the overlapping action, passive overlapping action. Let’s look at the weight gain and loss in a jump. In this case I’m going to jump and I’m going to measure the weight gain and loss using this force plate. So start the recording, stand on the force plate. Now I’m wearing a skirt, hula skirt, wig, all of these to give you more items to look at their overlapping actions. So the first part, as I’m dropping into the crouch, it’s actually accelerating downward so I’m going with gravity but then I have to slow down to come to a stop. So then I’m going against gravity, gaining weight and then certainly when I’m pushing up and gaining speed I’m going against gravity, so I’ll gain weight. And you can see this in the follow-through and drag of the of all these items of things get lighter, say fluffier, as I lose weight but then when I gain weight everything’s pulled down as if it was heavier. See this in the headgear. Then once I’m in the air, then I’m actually in a weightless state flying through the air. So everything is very light and flouncy, and you especially see this in the lei. And then on landing I have this office sudden deceleration, big gain in weight, everything drops down very quickly. So here’s the data from the force plate. So first there’s nothing. I step on the plate, this is my normal weight. Then I drop into the crouch, hit the, slow down towards the bottom. Then this part I’m pushing up on the plate so I have a higher than normal weight. Then fly into the air, I’m actually in a weightless state and then finally land on the plate and the weight shoots way up at that point. Now you may you might argue that this 0 when I’m in the air is because my feet are not in contact with the plate, but even if the plate was glued to my shoes as I’m in the air in a weightless state similar to the vomit commit video in an earlier tutorial. So in that case it really is zero weight as you’re flying in the air. So in summary…. They don’t necessarily have to be jump in the air and turn your head back and forth looking around has nothing to do with the jump. But an example of an active overlapping action that is in support of the primary action would be swinging the arms when you jump…. Passive overlapping actions occur in a jump, such as your hair flying or your clothes, and much of that motion is effected by weight gain and loss…. So hopefully that helps you understand what’s going on with a jump.