All language subtitles for CustomMetahuman_1.3.mp4

All right.

So let's have a look
at how the metahuman system is set up.

At the beginning,

all those folders and files
might seem a bit confusing,

but we don't actually need
most of the stuff here.

Nonetheless, let's quickly
browse through the folder structure

and then have a look at the character
in more detail.

I will cover the following topics
in this video:

The metahuman skeleton
or rather skeletons,

because we actually have two of them.

The blueprint and the materials
and textures of the metahuman.

This is actually quite important
to understand since this will drive

some of the decisions that we make
in our customization workflow later on.

When we import a metahuman to Unreal,

we get a folder
with the name of our character,

in my case, the "Hero" folder,

and another folder called "Common"

This "Common" folder contains
all the assets that are actually shared

by all metahuman characters
independent of the specific model.

Like for example, the metahuman base
skeleton, physics assets,

most of the blueprints, materials
and animations.

The character folder is the place
where all assets that are unique

to this character are stored.
Like the character blueprint,

the head and body meshes and textures,
hair binding assets, etc.

Since it is sometimes

difficult to find a specific asset,
for example the skeleton

in all these folders,
I usually go to the blueprints components

and then open assets from there.

Or use the locate asset function
to jump to the correct file.

Okay.

Now let's have a look at the skeleton.

Select the body component in the blueprint,
and then double click on the skeletal mesh.

In the editor, you can
show all the bones of the body skeleton

by going to -> character -> bones,
and then choosing All Hierarchy.

You can click on the bones
to select them in the viewport,

but a better or more precise way is
to select the bones in the skeleton tree.

Compared to a simple character rig,

the metahuman skeleton
is a bit more complex with lots of tiny

little bones with names
like Twist, Bulge, Corrective and so on.

All these additional bones
are used to approximate

muscle movement in the body and face.

Let me demonstrate!

You see how the chest muscles deform

or how the biceps and triceps
are actually bulging

when the arm is bent?

Even for the fingers, there are
small bones that control the deformation.

Let's have a look at the face rig now.

Open the skeletal mesh
editor and show all bones.

You see, the face rig is even more complex.

It shares a couple of bones with the body
skeleton like the spine and neck bones.

But all the other hundreds of bones

are responsible
for driving the facial movement.

If you go to the animation asset,
you can actually see

how all the bones are moving
when the animation is played.

So our finding Number 1 is:

The character has not one
but two skeletons.

The body and face rigs are separated.

This is, of course, not without purpose.

That's the beauty of it, because you can
assign an animation to the body

and then drop a secondary animation layer
for the head and face on top of it.

You can use either prerecorded animation

for the face
using Faceware or other software,

or you can use the ARKit live link
for Real-Time

Facial Motion Capture.

Cool, interesting.

But how does it work that the head
actually follows the body movements?

Although it runs on a different rig?

If you open the Face_AnimBP,

which is the blueprint for the head
and face animation,

and then open up the AnimGraph
you will find a small node connection

called Copy Pose From Mesh
assigned to the body pose.

This copied pose
then feeds into a layered blend node

where the two rigs are joined together.

Let's see what happens
if we disconnect the copy pose node

in the blueprint

The head then stops following the animation
assigned to the body skeleton.

If we reconnect it,

the head gets back into place.

Another thing

that we should look into
is the skinning of the character.

As with all animated character models,
the deformation of the mesh

is driven by the vertex weights
assigned to each bone.

The process of weight
painting is also called skinning.

You can inspect the vertex
weights directly in the engine.

If you go to the mesh editor,
click on -> character -> mesh

and then activate Selected Bone Weight.

When you select a bone
in the skeleton tree, you can see which

part of the character mesh
would be affected by the bone's rotation.

Let me show you the skinning in Blender.

For this, I export the body and the face meshes as FBX files

and then import them in Blender.

If you select the skeleton and then Shift-select
the mesh, you can go into weight paint mode

and see how bone
rotation affects the body movement.

Now, why are we looking at this?

Well, we have a small complication here.

The separation of the body and head meshes

happens somewhere below the clavicle.

That means that if we create clothes
for a metahuman character,

the skinning of the body
does not have any information

on the upper chest and neck apart.

To make matters worse, the skinning of
the head is not straightforward either.

There are no vertex weights
assigned to the neck bones

between spine04 and the head bone,

all the skinning is regulated
by a multitude of tiny bones of the face rig.

This will be important for clothes
modeling and skinning.

What is usually done
is we copy the weights from the body

to the clothes, so the clothes deform in
approximately the same way as the body.

But since there is no information
on vertex weights

for the upper chest part,
there is nothing to copy from.

We will see later how we can deal

with this issue.

Okay.

We have now covered most of the questions
concerning the skeleton setup

of the metahuman characters.

So what else do those characters offer
in terms of functionality?

Well, for one, both the body

and face come with a control rig.

If you create a sequence
and drop the blueprint into the sequence,

it automatically detects and displays
the control rigs.

This is very useful for keyframe animation
or for polishing

your motion capture animation.

For a faster workflow,

there is also a utility widget
called the

Metahuman Control Picker, which you can
find in the utilities folder.

Here you can quickly select
one of the controls and switch between

IK and FK, which stands for inverse
kinematics or forward kinematics.

The last functionality

we want to look at, are the face blendshapes.

The face comes with over 200 different

blendshapes
or morph targets for facial animation.

This is how these characters
can achieve an incredible quality

of emotional expression.

All right, let's wrap it up.

What have we learned?

First, when we work on the character,
we want all this goodness

to remain intact.

If we export the head, for example,
modify it, say, with the sculpting tools

in Blender, and then bring the FBX back
into the engine,

it will lose all the blend shapes, control
rig, etc..

Now, I know all of this
and much more is possible

in Maya, since the metahuman characters
come with the Maya source files.

But for Blender users, this presents
a real challenge.

And second,

clothes need to be rigged to the body skeleton

since the head follows
along with the body animation.

And we need to solve the problem
of the upper chest.

Also, something to keep in mind:

In case you are using the head rotation
with the ARKit,

those head movements
will not be transferred onto the clothes

So the use case will determine

what we can do in terms of clothes items.

The decisions we make concerning
the animation workflow for our character

will influence the options we have
when it comes to creating clothes, hair,

and other props.

Next, we will have a look

at the blueprint
of the metahuman character.

So the main asset really
where everything comes together

is the character blueprint, that is located
in the main character folder.

In my case, the "Hero" folder.

By the way, there are different ways
to open the blueprint.

You can either double click
on the blueprint asset here in the content browser,

you can click on Edit Blueprint
in the Outliner, or you can click on this

blue button and select Open
Blueprint Editor

with your character selected.

With the Blueprint Editor open,

let's go and have a look at the character
in the viewport.

On the left, you see all the components
that come with the imported character.

You see that the body and face
skeletal meshes are here.

Attached to the face
are all the hair groom components.

Each hair groom
component is always accompanied

by a so-called binding asset.

This binding asset is responsible

for the movement of the hair
with the face geometry itself,

so that the hair is not just static,
but actually moves along

with the facial animations.

Let's see how it looks...

In addition,
the blueprint already contains three slots

for clothing: Torso, Legs and Feet

for upper body clothes, pants and shoes.

Since we disabled the clothes
when we created

this character in the metahuman creator,
the slots are empty

except for the flip flops,
which I already disabled as well

To disable the flip flops,

just click on the Feet component
and under Skeletal Mesh

select Clear

You are, of course, by no means

obliged to use all these slots
for clothes.

As you can, of course, also assign
a full body outfit to the torso alone.

But this gives you some flexibility
in setting up your character.

We will see how this works in a later
chapter

when we come to
creating clothes for our Hero.

At the bottom of the list,

there is another component
called LODSync.

This regulates the level of detail
for all the components

that are in this blueprint.

In the details panel,

you can force a specific LOD.

For example, set
all components to LOD0

if you don't want your hair to disappear
at a certain distance.

There is already a whole program
set up for the character

in the main blueprint
and also in the Face_AnimBP,

among other things.

But we will look into all that
in another chapter of this course.

Basically, what we need to know
for the purpose of customizing

our character is:
First, when we design clothes,

it is good to consider that
the torso, legs and feet can be different.

We can also assign a full body outfit,
as I said, including shoes

to the torso alone.

So we don't need to always split clothes
into those three parts.

But this modular
setup allows us to be more flexible.

And second:

In principle,
we have little limitations when it comes

to adding stuff to our character.

We can create new hair assets,
clothes, physics assets,

and even attach static meshes to it
like goggles, hats and other things.

Almost anything is possible in the blueprint.

All right.

Next, let's have a look at the materials
and textures and see what we can work with

and whether there are any limitations
when it comes to texturing the character.

Let's look at the face first.

The main material instance for the face
is the very first one on

the material list called HeadSynthesizedBaked.

It comes with an extensive set of
parameters to adjust the look of the face.

The master material for the face can be found here.

Let's open it up.

The face shader is quite complex,

but we don't need to understand
every single node in the material editor.

What is important to know
is which textures we can customize,

so the character still works as intended

For us,

the two most important texture
sets are the base color

and normal map textures.

To achieve more realism,

the metahumans use several sets of texture
maps for the color and normals.

There are four base color maps
that are used to show

little changes in how blood flow
is affected by facial movements.

When you squint your eyes or open
your mouth, certain skin areas become more

red or pale, depending on the stretching
or condensing of the skin.

This is what these three additional
base color maps are for.

In the normal maps,

there are three wrinkle maps for the face
which simulate

the skin deformation
in the facial animations.

As a test, let's remove the first wrinkle map, which
is mainly responsible for the forehead.

You see,

the result is quite considerable.

Quite interesting to see

is that the face textures
have different resolutions.

The metahumans are not brute
forcing their way into visual quality

to achieve a high level of details,

the normal maps come at 8K.

(Remember, by the way, it depends which
download settings you used in Quixel Bridge)

but the base color map is only 2K,

since most of the details
are controlled by the normal map.

So the guys who made this, already
thought about optimization,

even for LOD0.

If we now look at the body material,
this one is much simpler.

It only has one base color map
and one normal map.

The texture setup is similar.

We have a 4K texture for the base color
and an 8K texture

for the normal map.

The last thing I would like to show you
is how the UVs for the body and face

are laid out.

The UVs for the face
first look like a total mess.

This is because the UV maps for the head
mesh,

the eyes, eyelashes, tongue and teeth
are all sharing the same UV space.

The only UV that is interesting to us
however,

is the HeadSynthesized material.

The body UVs are located on
the second UV tile.

This is important
to know for our texturing workflow.

So wrapping up:

When it comes to customizing textures
for our character, for example, changes

in skin color, tattoos
or whatever else we would like to adjust,

we need to consider the following:

First, the facial deformations.

This is concerning color and wrinkle maps.

How important are those
and do we want to keep them?

If we don't, then we just replace all
those additional maps with the main map.

If we would like to keep those,
we need to work

on all those maps separately.

And second,
if we want to texture the body,

and especially if we want to add texture
elements like chest tattoos

that cross over from the body
mesh to the chest part of the head mesh,

we need to use a UDIM
texturing workflow in Substance Painter

or whichever
other software we use for texturing.

Well, this concludes our
analysis of the metahuman character setup.

You can find the main points,
that we have discussed here,

also in the course book, by the way,
so you don't have to watch the videos

every time you would like to go back
to this character inspection.

And equipped with this knowledge, I think we are now
ready to begin customizing our Hero.

In the next chapter,

we will dive into a workflow

for creating and baking
morph targets for our metahuman.

You will learn how to deform the mesh of
your character without breaking anything.

See you there!