All language subtitles for 07_09_character_rig_constraints

- [Zach] In this video,

let's add the constraints
to our character rig.

So here I have the finished character rig.

Don't worry, we get back to the point

where we were before in a second.

Here I just wanna quickly
show you something.

For this character, I now
disabled all the constraints.

And now imagine we have
a cup of coffee here

and I want to now maybe
make the character sit down

and with one hand grab the coffee

and this should be animated.

So I go to Pose mode and
start positioning this.

So I have to make this down.

Then let's rotate the legs.

Then this here.

Then let's move this arm
down and this arm down.

And then let's maybe place
the cup somewhere here

in front of him.

And now I want to make this
arm grab the cup of coffee.

So that means I have to
rotate this and this.

Then make this arm a bit move upwards.

And something like this.

Rotate this here by pressing
double R, place it here.

Now we can see, Okay,
the hand is not really

at the position of the cup

So let's start over, let's
rotate this here, this here.

Yeah, this maybe looks a bit
better, but it's too high.

So let's, again, try this.

Ah, damn it, it's not
at the right position.

And in this case,

I may be not even able to move the cup

because it should stand on the table

and you can see it is a pain in the butt

to place the bones at the right spot.

And this whole process is
called forward kinematics.

That means we are adjusting a bone shape

from the start to the end.

That means we would start
with the first bone,

then the second bone, then the third bone.

So this is the forward way.

However, we wanna make
our life much easier

by using the inverse kinematics,

which inverts the whole process.

That means we can move the hand

and the arm will adjust automatically.

So let me quickly enable
the constraints here,

which I already have set up.

You will learn in a second how this works

and now I can just move
one target bone here,

which controls the position
and rotation of the hand.

And you can see that the arm
is adjusting automatically.

So, and you can see how easy it is

to place the hand at the right spot.

And the same works for the legs.

Let's enable here the IK,

which stands for inverse kinematics

and one other constraint.

And now down here I
can also use one target

and the whole leg is moving correctly

and also the hip is
moving the legs nicely.

And here you can see the clear difference

between inverse kinematic
and forward kinematic.

So here I needed to adjust
everything manually.

And if I move the hip,

oh man, then I have to
adjust everything again.

So now you know why we
need to set things up

just to make our life later
on when animating much easier.

And for that, let's get
back to our rig in progress.

So here we have our rig.

And in order to be able
to add the constraints,

we have to go to Pose mode,
which we can also do up here.

So this is not working in
Edit mode or in Object mode.

Then here we have to take care

because we have the object constraints,

which we discussed in the previous video

with the cannon example.

And we can also add
constraint to the object.

That means the whole
thing here in Object mode.

However, when we wanna add
constraints to single bones,

we have to use the bone
constraints over here.

So, and in order to set up the
inverse kinematic constraint,

or IK constraint, we
have to select the bone,

which is directly in front of the target.

Maybe you remember, we
added this IK hand bone,

which is like a loose
bone floating around,

and this should be the target,

which the arm and the hand should follow.

And we cannot just use
the hand bone as target

because this is connected
to the lower arm here.

And this just don't work
if the bones are connected.

So the target should be a loose bone.

Then let's select the lower arm here,

go to the Bone Constraints

and let's add the inverse
kinematics constraint.

And you can see the constraints
are pretty much the same

as we have for the object constraints.

So let's add the inverse kinematics.

And first of all, let's
pick the target object.

For that, we first have
to pick the target rig

because you can have
multiple rigs in your scene.

So in this case, it's rig_male.

And then we wanna use the
male hand IK L as target.

That means if I now pick
the target here and move it,

you can see that not only
the arm is following along,

but the entire rig.

And that's because we have to define

how long the chain of bones is

which should use this IK constraint.

And in this case,

it should include the lower
arm and the upper arm.

That means we have to set
the chain length to two,

and then you can also
see this yellow line,

which is pointing to the
kind of root point of the IK.

And now when I move this,

you can see how nicely the arm is moving.

However, I can see we you
forgot one little thing.

We forgot to parent the thumb bone here.

So let's quickly go to Edit mode.

Let's hide the IK bone
with H, it's in the way,

and then select this one,
then we shift this one here,

press Control + P and click
on Make Parent, Keep Offset.

Now let's press Alt + H
to unhide the IK bone,

and let's go back to Pose mode.

Now, when I move the hand here,

the thumb is also moving along.

So now when I move the target,
we still have two problems.

First, the hand is not
aligning with the target bone,

which is very useful,

and I cannot control the
orientation of the elbow.

And for that, we have this bone over here,

which should be the target of the elbow.

So let's set up the target here first.

Let's select the bone with IK constraint,

and here we have the Pole Target.

For that, we need to use the rig_male.

And in this case, let's
simply search for the elbow,

which we have over here.

So now you can see it's
somehow rotating wrong.

If I disable the IK,

you can see something is happening here.

And that's because by default,
the X axis of this bone here

is pointing to the target.

However, if you remember,

we set up that the Z axis is
pointing to the back here,

which is absolutely no problem.

We just have to change
the pole angle here.

And if you don't know in which direction,

just play around with this value here

to see where it should go.

And this is in this case,
positive 90 degrees.

And now if I disable and
enable the IK constraint,

nothing should change.

And now it means if I move this bone here,

the arm will rotate accordingly.

So I can position this one
here and then move this one.

By the way, if you moved
something in Pose mode

and to get it back to the rest pose,

simply select everything, press Alt + R

to reset the rotation and Alt
+ G to reset the position.

Now, the only thing is left here

is that the hand should
follow the rotation

of this bone here, because
the location is also correct.

It will follow the lower arm,

but it should rotate along
with the target here.

So let's select the hand bone.

And in this case, let's add
a Copy Rotation constraint,

and as target here, again,
we wanna use the male_rig

and the hand IK L bone.

And that's basically all.

When I now select this bone here,

you can see the hand is
following and it's rotating.

And the reason why I
set this up in this way

is that later on, I can
only animate the target bone

to fully control the arm position,

the hand position, and the hand rotation.

The only thing I can't control
here is the elbow position,

which we have to do with another bone.

But that means, instead of
animating all these bones,

we only need to animate two bones

to control the hand and arm position.

Of course, if we wanna change the fingers,

we also have to animate these two here.

Let's reset this,

and now let's do a
similar thing for the leg.

So, but here in Pose mode there
we have a special shortcut

to add constraints.

For that, we need to select
the target object first,

which is the IK bone here for the foot,

and then we shift the bone

where we wanna place the constraint on.

And in order to quickly
add the IK constraint,

simply hit Shift + I, and
then click on To Active Bone.

So it will be edited to
the active bone here.

And then the cool thing

is that both the rig and the target bone

is already added over here.

So now when I move the target
here and is doing something,

of course, we have to set
the chain length to two,

in this case, again, for the
upper and lower leg bone,

and now it's doing the correct thing.

However, we still have to set up the pole.

So let's use the rig here
and pick the knee bone.

And again, the orientation is wrong.

So let's play around
with the pole angle here,

which should be negative 90.

And now I can also control
the orientation of the leg

and I can easily move the leg.

And by the way, when we created the bones,

we added a little bit of bending

to both the legs and the arms here.

And this is now in this stage important

because when moving
the target in this way,

the arm knows in which
direction it should bend.

When you just make it straight

or have a bending into
the other direction,

then it would bend into
the other direction

or do something weird.

So that's why it is important

to add a little bit of
bending in Edit mode.

And by the way,

if you forgot to add this
bending in Edit Mode,

you can always go back to Edit mode,

grab this joint here
and just move it along Y

in this case a little bit.

But yeah, we have done
it, so it's all correct.

Now we still need to add
the Copy Rotation constraint

to the foot here.

And there's also shortcut
which we can use.

First, let's select the target bone,

then we shift the one where
we wanna add the constraints.

And then with Control +
Shift + C, C for constraints,

we can basically add any constraint now.

And in this case, we wanna
add the Copy Rotation.

And as you can see, again,

the target is automatically added here.

So that means I can move the IK bone

and the foot will follow automatically.

So when I now move the hip bone here,

you can see that the leg is
also adjusting automatically.

Same if I move the main hip bone here,

all the arms and legs
will adjust automatically.

So now there's one last thing left to do,

which has to do with
the two IK bones here.

When rigging a character,
we have this root bone here,

and the purpose of the root
bone is to move the entire rig.

And that's why you parent
all important bones

to this bone here.

And if I move this here,

you can see that I
parented the hip bone here.

However, I have not
parented that IK bones here.

They are just floating here in space,

and we could just parent the
IK bones to the root bone.

However, I wanna be able to disable

and enable the parenting.

So for example, when the
character is sitting in a car

and has its hands on a steering wheel,

then I wanna rotate the steering wheel

and the hands should be
attached to the steering wheel.

So I wanna be able to change the parent.

And for that, we can also use a constraint

which is kind of a parent constraint,

but it's called Child Of.

So let's edit Child Of
to the hand IK bone,

pick the rig as target, and
the root bone as bone target.

And by the way, when using
the Child Of constraint

and you add the target,

and then the object is like
moving in a weird direction,

simply hit the set inverse button,

and then it will get back.

And now if I move the root bone,

you can see that the hand IK
bone is also following along,

but I can always turn it off.

Now it will stay here.

And I could even change the influence

that it's only moving along a little bit,

which is not useful in this case,

but, you know, in some other
cases it might be useful.

And what I can also do,

I can easily change the parent over here

by selecting a completely
different object.

Now let's do the same thing over here.

For this, let's use a shortcut again,

let's pick the root bone
then with shift the foot IK,

Control + Shift + C, and
choose the Child Of constraint.

Now you can see this is set up correctly.

And now when I move this, the
entire rig is moving along,

but I can also attach the
feet to something else.

And by way, the elbow target
bone was parented to the hips.

So it will rotate and move with the hips,

which is something which is recommended.

And the knee target which
is parented to the foot IK.

That means if I rotate this,

you can see that the leg
orientation will follow,

which is also something
which is recommended.

Yeah, now we set up all
the important constraints

and in the next video,

let's learn about the skinning basics,

which basically means how to
connect a mesh with the bones.

And as always, don't forget to save.