Original subtitles

- Animation curves is one of the beginners' nightmare.

But I want them to become your best friends.

To display the animation curve of our ball,

let's go into the graph editor.

Right now, our curve looks a bit boxy,

not really curved, and this is because

we are still in constant interpolation.

But it will help us reading them.

The curve are just a graphical representation

of the value over time.

The yellow controller point accurately

the different key frame we have inserted before.

If I select the yellow point on the blue curve

at frame 7, it has a value of 4.

such as the Z location of our ball.

And if I now display all the object transform channel

in the graph editor,

we can see that the Z location is highlighted.

So the control point I've selected in the graph editor

is the key frame value of the Z location of our ball.

If I double click on one of these channels,

it will select all the control point of the current curve.

You can hide and unhide curve

as you would do with any object in the 3D view.

If I press Shift + H, I will hide everything

but the selected curve.

Or you can click on the little eye icon

to choose whether you want to see or not the curve.

With G, I can move the curve.

I can press G+Y to constrained the movement on the Y axis

or G+X to constrained on the X axis.

Before we start reading those curve,

let's get rid of any of the curve we don't need.

Since our ball is not rotating,

we can get rid of all the Euler rotation curve

by pressing X.

And we can also get rid of the X and Y locations

since our ball is just moving up and down.

This is a good practice to get rid of any unwanted channel

to keep your graph editor clean.

We can find the Z corresponding value

onto the control point of the curve,

but also in the transform channel of the object.

Pressing the N key will open the F-curve panel.

This is a little (inexact) here to check the position value

and interpolation mode of the key frame channel.

Let's now select all the key frames, press T,

and switch to Bayesian interpolation.

If we now play the animation,

we get way smoother motion of the ball.

When you switch from step mode to Bayesian mode

or curve mode, we call this the splining stage.

If we have a quick look to our curve now,

we can see that the Z location curve

is getting higher value when the ball is getting higher.

I will unhide the scale channel by clicking the eye icon.

I will select the first controller point of those curve

and press the dot key on the Num pad to zoom on it.

You can easily identify the Z scale channel,

which is in blue, allow us to control the height

of the ball.

And the X and Y that are one on top of the other

that allow us to control the width of the ball.

Let's check a couple of example to betterly understand

the behavior of the curves.

In this example,

the curve is controlling the rotation of the arrow

from a value of -90 degree to +90 degree.

The curve is rising rapidly

before easing into the frame number 24.

And when we scrub through the animation,

we can see that we have big spacing in the beginning

of the animation, and it gets lower in the end.

You seeing the motion we will have a preview

on the spacing of this animation.

And now, we can obviously see the difference of spacing

during the animation.

And the more vertical the curve is, the larger the spacing.

The more horizontal it gets, the smaller the spacing is.

In other word, the more vertical the curve,

the faster the animation.

The more horizontal, the slower.

In the next example, let's consider the X location curve

of the ball being the time.

It goes forward in a linear fashion

Now, if I activate the Z location curve,

and I frame it properly, look at all the Z location curve

and the motion path we on in the 3D view port align

or are comparable.

Again, when the curve is vertical,

the sphere will rise rapidly.

And as the curve gets more horizontal,

the sphere rise slower.

So if I now give an S shape to my curve,

the ball will move slowly in the beginning,

then in the middle of the animation,

it will accelerate as the curve get more vertical,

and in the end, it will slow down.

We are creating an easing out from the frame zero

into an easing in the frame 24.

And since we still have the linear motion

of the sphere on its X axis,

we can see that the Z curve really looks like

the motion path of the sphere.

Since my sphere is moving on the X location

in a linear fashion, any modification I will add

to the Z curve will show in the 3D view

as in the graph editor by updating the motion path.

You can use the few example available in the file

to play with the curve and recalculate the motion path

and check out the spacing.

Back to the rotation example,

I've modeled the curve so that

I have a fast acceleration in the beginning,

then a plateau, and then an ease out and ease in.

And it absolutely reflect on the motion path.

The pretty vertical shape of the curve

on the first two frame generate a big spacing.

The plateau shape or flat shape of the curve

indicate that the value is not changing over time,

so the arrow will stop,

while the final S shape of the curve

show an acceleration then a deceleration

into the final frame.

To summarize, we have seen that a curve is just

a representation of the evolution of a value over time.

The more vertical the curve shape,

the faster the value change.

And it translates in bigger spacing.

The more horizontal the curve, the slower the change.

Motion wise, it translate in smaller spacing.

A flat curve indicates that there is

absolutely no change in the value

and so no motion.