Our next principle we're gonna learn is slow in  and slow out, otherwise known as ease in and ease out. And it's basically a reflection  of Newton's first law of motion. So we're gonna get into a little more science  and physics here,  but it basically says an object at rest  tends to stay at rest. And an object in motion tends to stay in motion  unless another force acts on it. And in our case, living on earth  and being a human, uh,  those forces are typically gravity, friction. And you know, in animation you could have the forces  of another character or object.

So we need to root our animation and motion  and familiar forces, even if we're going to caricature them  because our eyes are used  to seeing things move in a certain way. When they break those rules, it can be a bit jarring  and distracting as opposed to charming and inviting. So even Walt Disney said that our work has  to have a foundation of fact in order to have sincerity. And what that means is it just needs to reflect  what we're used to seeing to some degree,  even if we're gonna going to caricature or exaggerate it,  because we are used to seeing things move in a certain way  based on the real world physics that we live in  and expect to see in motion of objects. So what that means in practical terms,  if you're animating in 2D drawing,  that means there there would be more drawings,  or if it stopped motion, there'd be more pictures. Or in CG animation there'd be more frames  or more poses at the beginning of, of a motion, um,  as opposed to the middle of a motion.

So if it was slow in  and slow out, it'd be more poses at the beginning  or more pictures at the beginning and the end. So the middle would be the fastest area  and that would be covering the  most distance for that object. So from a stationary position,  I'm just gonna move it in real time. It would kind of look like this. It starts slow and then speeds up and then slows down again. So that's how we expect things to move.

You know, if you consider a car for example, you know,  there is some, it has to overcome the friction  of the ground, the weight of itself, or gravity. And you know, it's a, it's a measure of how fast the car is,  how quick it can get to zero to 60 kind of a thing. But there, there is a slow out no matter  how fast the car is. It can't just completely, you know, shoot off like,  uh, the speed of light. Um, things have to overcome these physical forces. And so that's what we can reflect in our animations  to give it that authentic feel and appeal.

Now, if you animate without this principle in mind,  it can make your animations look quite robotic  because robots move in a more linear fashion. And the instant torque of electronic motors kind  of allows them to overcome those initial, uh, forces  that we aren't used to seeing as much. So, you know, I'm moving a bit more fluidly,  but if I was a robot, I, you know,  it's a bit more jerky motion and that's a linear thing. So, you know, if I was to do the same example  with this little toy, it would be even the entire time,  it wouldn't speed up or slow down  from the first time it moves, it would be the same speed. Now, even if you slowed that down  because I'm a human moving it, you'd be able to tell that I  was slower at the beginning and slower at the end. 'cause I'm trying to stop my own, the weight of my own arm,  uh, even from going, let alone the weight of this.

So it can be important to know that, to  avoid robotic looking things  or to embrace it like I animated robots on the movie, one  of the Transformers movies. So it's important to know when you can break these rules  and intentionally lean into breaking them. And one of the most common exercises in animation to help  sell this principle is a character lifting a weight. And that's because the weight is imaginary. We're we have to put  that weight into the object through these principles. And one of the main ways is ease in and ease out  because a heavier object will take a lot more  force to overcome gravity or it's, or that object's mass.

So, you know, if I was to pretend  that this object was really heavy, I would do a lot  of different body maybe motions,  but you know, my arms would get straight and I'd pull  and it'd go very slow. If this thing was very light like it is,  I would just do this and it would  feel light and it would look light. So when you're animating, it's all made up. So you have to mimic those actions  to make it feel heavy or light. So let's take a look at the bouncing ball  example one more time. But instead of on the left side, uh, it having no squash  and stretch, we're gonna have it have no ease in  and ease out or slow in and slow out.

Can you see how the left ball feels robotic  and feels as though there's no weight to it,  but the ball on the right at the top of its bounce,  it slows into the top position  as gravity slowly overtakes its motion upward  to begin slowly pulling it down again  or to slow it out back into that falling motion. A mistake to look out for when you're starting  to do these types of exercises  and a bouncing ball, what I see a lot of time is  students ha having just learned this principle  and doing a bouncing ball test will actually slow a ball  down on impact. Now the ball doesn't know  that it's coming close to the ground. So the, we have to think about what,  why, why would it slow down? The force acting on it is consistent and it's gravity,  and if there was no table there  or floor there, it would just keep falling  until it reach reaches terminal velocity like  you do on skydiving. It would just keep falling until that falling is interrupted  by the ground, which is hopefully not like skydiving.

So just because you're starting  to grasp this principle doesn't mean it needs to be applied  to every situation. Like that falling ball example  or any falling object really, it will continue to speed up  until it reaches terminal velocity,  unless something intercepts or interrupts that falling. So when something is, is falling to the ground,  It just keeps speeding up. It doesn't decide, oh, I'm getting close to the ground,  I'm gonna slow down. Right? That doesn't make sense.

So look out for stuff like that and,  and really start to wrap your head around this principle in  the context of exercises like that. So one term you might hear in animation  and especially in regards to slow in and slow out or ease in  and ease out is the term spacing. And spacing refers to the amount of distance between  each pose basically. So let's take a look at the bouncing ball example one more  time just so that we can learn this new term as well  and how that applies to this principle. So if we look back at the bouncing ball on the left,  it has even or linear spacing. The speed stays the same on the way up  and on the way down, which means the distance  between each pose is the exact same, that's even spacing.

So that's just not physically correct in this case, right? So it's also boring to watch. Even spacing doesn't help communicate the weight  of the object, and it feels quite robotic as well. So because the ball on the left is even spacing,  you might think the ball on the right is uneven spacing,  but that's not the case. The ball on the right has a gradual incremental,  consistent change as it slows into the top and slows out. What uneven spacing means is that it has  an inconsistent distance between each frame.

So instead of a gradual change, it could be a big change  and then a small change, and then a bigger  change than the last one it had. And then a smaller one than the third. There's no, there's no consistency to the motion. So it can feel quite erratic  and it can happen sometimes in animation when you are having  a hard time keeping track  of more complicated animations like character animation when  there's a lot more moving pieces. In the next lesson, let's do our first stop motion animation  exercise and get a little practice using ease in  and ease outs or slow in and slow outs. I'll see you in the next lesson.