Original subtitles

- [Instructor] We are slowly but surely getting close

to the end of this chapter,

as we just need to polish the arm of our character.

It's gonna be very easy because we will deal

with the arms as a simple, overlapping motion,

animating the shoulders in reaction to the torso

the arms in reaction to the shoulders,

and the forearm, hands and fingers

in reaction of their parents in the chain.

To polish the shoulder, I prefer to hide the arms.

They bring a lot of motion to the screen,

and that could be distracting.

As usual, for most of our forward kinematic controllers,

I will start with the rotation.

The X rotation channel drives the rotation

that goes up and down on the shoulders,

while the Z rotation drive the forward

and backward motion of the shoulder.

We will then slightly adjust to Y rotation curve,

but without that much amplitude, because if you remember

in the rotation video, I explained

that if we go too far with this third axis,

we may encounter gimble lock.

Here, I'm starting with the X rotation curve

that drives the up and down motion of the shoulder.

Editing this curve will be pretty straight forward,

as we are animating the shoulders in reaction

to the torso motion.

Whenever the torso is raising, I will lower the shoulder,

and whenever the torso is falling,

I will raise the shoulder,

and we need to bring extra contrast on the extremes.

(mumbles) polishing the chest for the open-and-down motion,

we generally mirror or repeat the cycle over 16 frames,

as the chest is aligned with the center of gravity,

whether we were stepping with the left foot or right foot,

we had the same up-and-down behavior,

but in the case of the shoulder, there will be a difference

whenever we are hitting with the right foot

or the left foot, since the chest

is leaning left or right in those cases.

This is why I'm polishing the whole X curve,

not only the frame from zero to 16.

Goal is to add a bit of overlapping motion

to have a relaxed shoulder behavior.

We'll add extra bounce using the Z location curve

a little later on.

The Z rotation curve on the shoulder

(indistinct) drive the forward-to-backward motion

is way easier to understand.

It looks like curve that we have already edited before.

The fast transition motion, before we ease,

whether in the forward position or the backward position.

Boom, there is a slight plateau to hold the pose.

(indistincT) bell-shaped curve will give you

a very smooth motion, while a more stepped curve

will you give you more contrast in motion.

My preference goes generally

toward a more contrasting motion, which is more interesting.

The curve is just about the twisting of the shoulder,

which on a human being, is super subtle.

Bend is like a few degrees.

In this regard, I'm mainly smoothing the curve

so that this wide rotation curve

doesn't show that much on the animation

and we don't get any popping issues.

While I would like to add extra motion to the shoulder,

using its Z location to bring a bit of up-and-down bounce,

I've decided to mirror the motion

onto the other shoulder right away.

The idea is just to check

if the current polishing of the shoulder

is satisfying before I bring extra details.

I've done this a lot of time.

You can complete the curve from one shoulder,

then go on to the other.

Press control shift to V to paste them

with the mirror option, and then duplicate them

on the whole length by 32 frame

and offset them back by minus 16 frame.

As explained before,

I want to bring a bit of extra motion

with the shoulder bounce.

This might not be a good idea on a very slim character,

but since our character is pretty muscular,

it will bring extra weight to the shoulders

and they will look very relaxed.

So I have isolated the Z location curve

by IDing all the other ones.

Try to focus on the chest motion.

As the chest go down,

we will make the shoulder drag up.

There is a lot of compression, or impact,

on the chest on frame four.

So I'm hitting the lowest position for the shoulder

two frames later on frame six.

Then the character hit its highest point around frame 10.

So again, I'm pulling the shoulder up at its highest point

around the frame 12, two frames later.

There is no impact on the up pose.

This is why I have a hold on the pose, or a slight plateau.

The shoulder hits its extreme high pose around the frame 12,

and then it drags as the body is going down.

So it's keeping its up pose a bit

while the lowest (indistinct) changing the curve

on frame six and 22,

mark the impact after the contacting frame.

Again, our curve doesn't perfectly repeat along 16 frame,

since the torso is leaning left or right

during those 32 frames.

So as the torso is leaning to the right of the character,

I'm (indistinct) the up pose of the left shoulder.

I feel like I've reached a satisfying motion

for the shoulder.

I've run a strength test.

So basically, I will increase or decrease

the scale of the current curve and see how it looks.

It will increase

or decrease the up-and-down motion of the shoulder

and make it more or less noticeable.

To do so, we will need to use the 2D cursor

as a pivot point.

So I will first position it properly

by going into the view tab and setting its Y value to zero.

Then in the pivot point selection,

I will select the 2D cursor as being the pivot point.

With all the control points selected,

I can press S to scale and Y to constrain the scaling

along the Y axis of the curve.

Increasing the Y scale

will increase the amplitude of the motion

and make it more noticeable.

Decreasing it will make it more subtle.

What I advise you is to scale the curve

while playing the animation.

This way, you can have a real-time feedback,

that generally feels better than modifying the curve

and then playing the motion.

Once I'm happy with the result,

I will mirror the curve onto the other shoulder.

Don't forget to check your motion from every angle.

For the up-and-down motion, we can clearly see it

from the back view of the character.

It's great to make this up-and-down motion noticeable;

don't overdo it, though.

In the next video, we are going to polish the arm

for arms and hands.