Weight gain and loss. Now if you take a heavy object and you lift it up and down, I think you'll agree you notice that the object feels heavier sometimes and sometimes it feels lighter in your hand. Now if you look at this carefully, you realize that that apparent variation in the weight of the object depends on whether you're going with gravity or against gravity. Now going against gravity would be if you're lifting it and speeding up. On the other hand if you're lifting it but then slowing down then you're going with gravity. In other words if you throw a ball up into the air when the ball is going with gravity it's rising and slowing down. Now the ball when it's falling it naturally speeds up and so going with gravity with the object that you have in your hand you're going with gravity if you're lowering the object and speeding up but then if you bring it to a stop as you're coming down then it's coming down and you slow it down and then you're going against gravity and at that point the object should feel heavy in your hand. Now this kind of variation of weight you could call dynamic weight and this same variation of weight occurs with characters. So for example in different stages of a jump I say that the character first starts to drop into the crouch and so they're coming down and speeding up and during that part they're losing weight. But then when the characters in the crouch and starts to push up then they're gaining speed going upward at that point the character feels heavy so if the character has gained weight going against gravity. Then at some point the character is rising and slowing down in fact while the character is up in the air the character is just as the beginning of the jump the characters rising in the air and slowing down at that point they lose weight and then on the very last stage of the jump in the landing during the squash of the landing the character is falling but slowing to a stop and in that settle the character it's as if they gained weight. Now these variations of weight gaining weight and losing weight we can measure this by using a digital force plate. This digital force plate that you see me standing on is essentially just an electronic bathroom scale that can record data on my laptop and then the weight is displayed here on this projector screen and you'll see in the next clips that I will be either gaining weight or losing weight depending on whether my motion is going against gravity or with gravity. So let's look at the first clip I'm just going to be going moving my torso up and so let's play this first clip. Now if you watch that carefully you'll see that for example here I am rising and speeding up so here's two frames and if you look back on the graph my weight is going up it's already larger than my normal weight of about 180 pounds. I'm rising and speeding up so I'm up to 240 pounds and in fact as I'm speeding up even more my weight rises to an impressive 322 pounds. Well let's look at another example and this one I'm raising and lowering just my center of gravity by flapping my arms. Now watch the screen in the back you see the graph and you see how my weight is varying up and down as I'm flapping my arms. So here my normal resting weight would be about 180 pounds but these weight changes go all the way down to a weight of about 50 pounds and up to about 270 pounds simply by the fact that I'm raising or lowering my center of gravity by flapping my arms. Let's just look at one more example. So very general motion I wouldn't call this dancing it's more like flailing around so there you are. Now this variation in weight is noticeable in character effects so you see this in the characters clothing the hair the character has fur so forth this variation in weight is visible in these character effects. Here's an example watch the woman with the red hair watch her hair as she's walking. Here it's in slow motion make it easier to see those variations of her weight reflected in her hair. Now Richard Williams in the animator survival kit describes this or he calls this counter action and there he writes when the character goes up the drapery or hair or soft bits go down. So here in this illustration from his book the character is coming down and speeding up so she's going with gravity losing weight this next pose she's moving upwards and speeding up and so it's as if she gains weight everything on her body her hair clothing her body itself seems to be heavier. Let's see this in a short clip from Madagascar 3. So watch Gloria as she's running in this scene we see this counter action in her body so if you if you look carefully you see sometimes she's lighter as she's going with gravity say falling and speeding up but then in other parts of her run she's going against gravity say also falling but slowing down coming to a halt at the bottom of her step and in that case she gains weight and we see this and especially in her lower body now I should mention that this variation in weight gain and loss you can also understand this in terms of follow through and drag so she's coming and coming down in the step and because of follow through her body continues moving down so this idea of weight gain and loss is not different from follow through and drag this is just another way of understanding this effect so in in summary weight can vary when an object moves up or down and that depends on the acceleration so if it's accelerating downward going with gravity then it's a weight loss if it's moving upward and speeding up it's weight gain so so here's this weight increases when the motion goes against gravity such as rising and speeding up or falling and slowing down weight decreases when the motion goes with gravity such as rising and slowing down or falling and speeding up and this weight gain and loss in animation is sometimes called counteraction and it's especially noticeable in character effects now you shouldn't confuse this with weight shift weight shift is a different concept and that's covered in another tutorial