All language subtitles for 04-04-01 Leg motion

- [Pierre] In this video, we
will start animating the feet

based on the root of the torso motion.

The first thing to do

is to double the length of
the motion we just created.

And we need to repeat
this up and down cycle.

With all my curve controllers selected,

I will duplicate them.

But first, make sure that
the very first controller

and the very last are exactly the same.

Then press Shift + D to duplicate

and offset by the length
of your animation.

In my case, 36 frames.

So that my whole cycle
run through 72 frames.

Again, this is the rhythm I
have chosen for this animation.

Your animation can be faster or slower.

From there, I will press Alt
+ H to un-hide my controller,

select the visibility property bone

and they will re-enable the legs.

Since the legs are using an
inverse kinematic mechanism,

we will just have to
animate the foot controller.

The cool thing with this animation method

is that it's easy to tweak
the position of any controller

by slightly offsetting the curves.

If I want to raise the up and
down motion of the character,

I just need to select the root controller

and offset the whole curve

on the y-axis in the graph editor.

The up and down motion will occur higher,

giving more space for the foot motion.

But it doesn't matter, even
if it doesn't look good

I will be able to get back onto this curve

and offset it at will.

The first thing to do from there

is to position our feet based
on the motion of the torso.

Generally, the up pose,

the moment where the torso
is at its highest point

is close to the passing pose.

It is generally slightly delayed.

When the foot contacts the
ground, the torso goes down.

And when the foot is pulling
back, the torso is raising.

Since the torso is almost at
its highest point on frame 20,

I will slightly move the
foot back on this frame.

And on frame zero,

whenever the torso is at its lowest point,

I will push the foot forward.

The idea is not to get 100% accurate

but just create a few landmark

before we use the curve
and adjust the rhythm.

Finally, the foot will be
third or away on the back

whenever we have just hit the down pose.

And then when the character
is pushing on the other leg,

the current foot will be raising.

The idea here is to work only on one axis

as we did for the torso,

setting the position of the foot

just before it leaves the ground.

Finally, I need to find the moment

where this foot will get back forward,

and this should have happen
just before the body is falling.

The foot contact the ground

and then we have the
down pose of the torso.

Our animation doesn't look pretty at all

but at least we have the main landmarks.

Since the forward motion of
the foot will be mostly linear,

I will select all the
key frames of the foot,

press V and change the
handle type to vector.

As we did before with
our squirrel character,

we will consider the cycle to be linear,

meaning that the character is
moving at a constant speed.

Hence, I can remove the
key frame prior to key 33,

because we just need to key frame,

one starting point and one and point

to create this linear motion.

Let's switch to the graph editor.

To get the right pace of
the foot when on the ground,

I need to interpolate from
frame 60 back to frame 33

through the whole cycle.

Because frame 59 or 60 mark the moment

our character is
contacting with the ground,

while frame 33 is the moment
the foot is leaving the ground.

So this plateau is not correct

nor the interpolation between
frame zero and frame 33.

But what I can do or what I should do,

because I've made a slight mistake,

is to duplicate the key
from frame 34 on frame 105,

which stand for frame
72, the end of the cycle,

plus frame 33.

This way, between frame 60 and frame 105,

I have the whole motion of the
foot sticking to the ground

with the right interpolation.

From there, I can go on frame
72, the end of the cycle,

and insert a key frame on this channel.

I can now duplicate to this key frame

and move it on frame zero

and set both to free or to vector.

Now, both the first and
last key frame are the same

and they have the right interpolation

and the foot is moving at the
right speed on the ground.

Now I just need to work
on the up and down motion

between frame 33 and frame 60.

We can also adjust the moment

the foot is leaving the ground,

I think it could happen a little later.

Now that we know how to
fix the interpolation

between the beginning and
the end of the motion,

that's perfectly fine.

The other thing to consider

is that while the foot has
linear or motion on the ground,

it won't have linear motion in the air.

By rotating this handle,

I will create a slight overshoot backward

as if the foot was projected the backward

because of its inertia
when leaving the ground.

With this row editing done,

I will switch to the Z location curve

and they will simply add a new key frame

between the landing pose,
between the contacting pose

and the pose where the
foot is leaving the ground.

As usual, you can see here the final curve

for both the Y and Z axis.

As I did for the torso, to get
a satisfying sense of weight,

I will make a slight
plateau or moving halt

just before the foot hit the ground,

so that it will have some
kind of a hard time to raise.

It will stay up before
landing very quickly

because it's very heavy

and the robot is kind
of releasing the foot.

So it creates some kind of
nice contrast on the curve

that currently translates
on the animation.

The tricky thing about this method

is to focus on one motion at a time.

And here, you may find out
the motion looks a bit weird

because there is no rotation in the foot.

But we will input some
rotation in the foot

slightly later on.

Just focus on one channel at a time,

one controller at a time.

And even focus on the motion
of the controller itself.

Not necessarily the
motion of the whole robot.

As any other animation technique,

it will take you a bit
of time to get used to it

but it's very handy for
this kind of animation.

Before we call the base
motion of the foot down,

I want to slightly push forward the foot

just before it lands.

To do so, I've slightly rotated the handle

just before the contacting pose,

so that the foot gets
a little more forward

before it hits the ground.

From there, I can adjust
the up motion of the foot.

Don't hesitate to track
the arcs of your animation

using the motion path we have
seen in the previous chapter.

In the next video,

we will use the foot roll controller

to add a bit of rotation on the
ankle and on the whole foot.