Original subtitles

Welcome to another blender cookie tutorial my name is catcher mail

and in this video we're going to be taking another look at realistic skin shading

with blender.

So far we walked through this subject twice already.

Once in depth with the blender internal render engine in the realistic head series

and then we briefly touched on it

with cycles as in the pancake hobo course.

But thus far we haven't gone in depth with skin shading in cycles yet

so that's what i want to do.

Now if you've watched any of my training before hopefully you know right away that

the first order of business is taking time to observe reality

and for human skin this is especially necessary.

Because everyone see human skin every day and subconsciously knows precisely how it's

supposed to look.

That's why it's so hard for cg artists to get right because if it's the slightest bit off

we all can tell and the illusion is broken.

However understanding why human skin looks the way it does is another story

knowledge that isn't so common.

So please study as many reference for autographs as you can if you want to create a

believable skin material.

But since i have gone over skin observations before in the pancake hobo course.

I'm only going to hit the basics here

but if you want a more detailed explanation

please go see the skin lesson in that course.

So the buzzword when it comes to skin shading.

Is subsurface scattering

and this is basically a fancy term for translucency.

If we take a look at this reference photograph.

It's a very typical studio lighting setup

with very harsh back and rim lights which are pushing a lot of light through the ear

here and this is

typically when it comes to subsurface scattering and human skin

most people look straight at the ears because that's where the effect is most

noticeable and you can get a very bright orange red glow

and this color is what bleeds through the shadows

and softens the shadows.

Notice here at the nose.

If we zoom way in and then if i just right click and hover over.

The edge of our shadow

notice just how red the color is

that's actually happening on

all the shadows across the skin

and this is the key thing that i want you to take away from this observation

and that we will need to recreate

as we pull back out in general

the effects of sub-surface

causes a softening of the shadows and therefore a softening of the skin

detail

and as far as the orangish red color that is coming from.

Different layers underneath the surface of the skin

like blood like muscle and fatty tissue that combine

to give us that color as the light scatters through it.

And with all that in mind

let's jump into blender and take a look at the assets we have to start with.

So this comes from a personal project that i

did a couple of years ago.

It's a slightly stylized and

elderly man head

and the reason i want to use this is number one there is a ton of detail

built into the geometry

through a multi resolution modifier up to level five.

If we jump up to that level you'll see

all the skin and pore detail that I've included

in the actual geometry.

You can

see how heavy it is.

Considering the viewport

sluggishness now

and it's important that this is included in the geometry

meaning that it's breaking the silhouette

it's not only included in a bump map or some kind of cheat but it's actually

affecting the shape of the geometry this will

help to ensure

a more believable.

Subsurface scattering effect

so let's pump that back down to let's say level two.

And along with this very detailed.

Piece of geometry

i also have.

All the texture maps that i painted.

Specifically for human skin.

Things like.

Epidermal texture map and subdermal texture map.

Bump maps subsurface scale maps specular maps

all the textures that i would need for a realistic skin shader

have already created it just needs to be plugged into a shader appropriately.

So before we actually create the shaders let's go through through.

The render setups that i have i'm just going to split my user interface over here to

give me a very small.

Render viewport

and i should have a camera let's at zero there you go.

Making sure that i'm in the cycles render engine I'll go ahead and enable.

Viewport rendering or shift z in that viewport.

And we have a black silhouette because i have no lights visible

so let's jump over to my

layer management add on and enable

layer rin a.

Which is my firm first lighting scenario.

Pretty standard stuff with.

A strong key light.

A.

Back slash rim light

and then.

A large card which acts as a sort of global rim light that i will show up

particularly well.

With reflections

and then then let's go to the next one rin b.

This is a actually very similar except that.

I would change the world value so let me go choose a

environment map.

I will of course

include some environment maps in the source files.

And do

ok so if i bump this up to let's say point five.

Now we have a lot of environment lighting contributing to our shadows lightening them

up a whole lot

and then finally we have render scenario rio see.

Which if i

let's say turn off my environment light again

this setup is useful for looking at how back scattering works through the ears

and if

my sub surface values are good.

So yeah the reason i show you these is

in order to get the best

skin material.

You'll want to look at the shading through different light setups

and if it looks good in all the lighting situations then you can have confidence

in your material.

So i think I'll start with

scenario a.

Just because

it's a little bit more neutral and standard

and let's get started building materials lrs.

I'll switch my

three d viewport to the node editor

with the n key

and right now i have one of my cards selected

but if i select my head geometry over here.

We have no material associated so.

Let's create one

and i'm going to call this skin underscore simple.

Because i'm going to walk you through a couple different

skin shading setups

obviously i named this one simple so the first one is going to be a fairly bare-bones

approach just using the subsurface scattering node

and textures associated with the model

and then after that I'll show you a more complex

approach to sub surface scattering specifically for skin.

With Matt heimlich support of the Arnold skin shader

which has all the bells and whistles of three layer skin shading.

That you may be familiar with if you come from the re

mental ray.

Are obviously Arnold

but being more complex

means that it actually rings hers about half the speed

as the simple setup

and you can actually get a very believable result with the simple setup but

still i think it's good to know both ways.

So now let's introduce our subsurface scattering node with shift a.

Shader subsurface scattering.

And we'll remove our diffuse b sdf

and plug in the bss rdf output into the surface input.

And immediately we can see in our viewport.

That.

Way too much light is now penetrating the surface and scattering around

it's glowing way too much

so the first setting i usually tweak is going to be this scale value right here

where the higher the value

the easier it is for light to penetrate and the further through the surface it can

penetrate

the lower the value.

The harder it is for light to pass through

the surface and it doesn't go quite as deep.

So let's bump this down.

Two point one.

And you'll see that

less light is able to make it all the way through the ob checked and our shadows

appear

and if we go

down a little bit more let's go two point one five cut it in half.

Our shadows get even darker and more of our model starts to appear while we still

have a lot of light shining through especially.

In the ears

because they're the thinnest part of our head mesh

but that's still a little bit too high hi.

How about a point one three.

I think that's going to be a good value based on.

My exploration of this shader

and now with that dialed in it'll be a lot easier to go over these settings which i

will quickly

run through first we have.

The fall off algorithm that we can select.

Where i kind of look these in reverse order from bottom to top where compatible

is the old algorithm that's about to be phased out and removed from trunk so we don't

need to worry about that at all

and we're going to be left with cubic and goshen

cubic is a sharper fall off based on the documentation

and it actually renders a little bit faster

but then

goshen is slightly more complex of an algorithm so it takes

a little bit longer to render but it's perhaps a little bit more physically accurate

though when i compare the two i really don't see any noticeable difference

aside from a slight render time savings with cubic's i'm going to select that it is

the default or it should be

a below that we have color this is the general color of our object so if we.

Do let's see switch that too let's see zoom out here.

Switch that to green

you know it looks like a green object that scatters

which is probably pretty obvious to you of course that's what that does but with

subsurface scattering if we jumped down we've always.

As the scale option here below that we have radius

and

this is where we control.

What color the scattered light becomes

so if you remember that reference image we just looked at.

In the shadowed areas on the edges i pointed out how red the shadows were and this is

the scattered color glowing through the sh shadows and with skin it happens to be red

so if we open up those options we have three values with a really no description

but the first one is the red value

the second one is a green value and the third is the blue value so

rgb which gives us

an overall color.

So again with skin we're looking for a row red color so let's leave

the first value at one

and then start to decrease the green and blue which should leave us with more red.

So let's

bump these down to half point five point five.

And you'll start to see that we get an overall green color of our object

but the light that passes through

causes it to glow low read

and i think i want it to be a little bit more orange let's.

Remove the green color take saturation all the way down to zero

and.

Okay yeah so i don't have any green interfering and it's clearly a very red color

so in the radius let's.

Bump down my blue value.

So now we have a lie little bit more green in the mix which should

take it closer to orange or if i bump that up to point six.

Yeah we're starting to get.

A little bit

closer to orangish yellow

but still mainly.

Red.

All right i think that's good for the radius that is a very important setting i would

say radius and scale are the most important

but we have a couple more options

below radius we have sharpness.

Now.

What i can tell sharpness does

is kind of the same thing as decreasing scale

but just to support my theory on what it does let's go ahead and do.

A couple renders

number one we will render this with

sharpness turned off.

Then let's

switch to let's go to slot seven.

And.

Go back to the node editor

by hitting escape

and

let's change our sharpness all the way up to a value of one.

And render that again.

And now if we switch between slot eight

and seven.

You can see

in slot eight.

That.

The details especially in the forehead around the eyes

and will generally the front of the face it gets a little bit blurrier

but then.

At seven they sharpen up a bit.

But also there seems to be more light passing through the ears the glow gets a little

bit bored brighter.

So on

changing the sharpness setting is not exactly the same as.

Simply dialing down the scale

but

it's some sort of in-between that tries to sharpen

the details of the geometry

while still maintaining that scatter amount.

And jumping back to the node editor.

I usually leave sharpness off.

Because i.

Kind of think it detracts from the believability a little bit

but abelow that we have texture blur and this really only.

Is noticeable when we're using a texture

because it does exactly what you would expect it blurs that image

and the idea behind this is if you read the docs

it states how and.

For example if we used a photograph to create our textures.

It's already blurred there's already blurring happening

within the sub surface effect because the picture is of subsurface skin.

Whereas if we hand paint a texture we might not necessarily build that in

and especially if we use a

procedural

we'll want to blur based on the subsurface scattering algorithm

and that's really where this comes in handy so i rarely ever touch the texture blur

setting.

And that is all for the.

Features of the subsurface scattering node.

Do note that if we switch to goshen

we lose the sharpness option.

Which again lends itself

to me believing that sharpness is more of a cheat effect rather than being

physically accurate

but

anyway other than that that's.

All all for the subsurface scattering node

and we're ready to plug in our textures so i'm going to add an input texture

coordinate node.

Way over here off to the left

and then add input.

I'm sorry not input texture image texture.

First we're going to load

and

our general head.

Color texture

let's enable thumbnails so we can see exactly what we're looking for.

This is what i want head color right here.

And then

let's plug in our uvi to the vector.

And the color of our image into the color of our subsurface scattering node.

And right away

you know it looks a little bit more human

though.

In general the whole texture feels a little bit too orange.

So

let's

add.

A.

Letter see color

rgb curves note

in between the image.

Color output and the subsurface scattering node

and for the red channel.

I'm going to take the right upper corner

and just drag it down a little bit.

Then jump to the green channel

and drag that down about half as much.

Yeah that feels a little bit more natural.

Maybe a little less

red.

Air ago that feels better

and that's really it for having

a texture plugged into subsurface scattering color

but we can also use textures for everything else so i'm going to show you

what a scale texture does and

with shift control d.

To duplicate the image texture node while maintaining the connection to the texture

coordinate node

and let's go open another texture.

That i have already created and i have two different versions of this it's called ss

as scale and ssl as scale beep.

Now scale b was procedurally created by simply inverting

the head mesh and then baking an ambient occlusion map.

That will conveniently give you darkened areas

around the thinnest portions of the mesh like the.

Ears

the eyelids the nose and lips which is

you

if you want to control the scale that's where you're going to want to control it.

Sounds pretty cool but this first one is what

I'll use and it's just simply hand painted

around the.

Ears and the eyes so let's go with that one.

Both of them will be included in the source files for you to play with but.

Ok so now if we plug this directly the into the scale value.

There will be absolutely no subsurface taking place

in the majority of the head as you can tell but then

the eyes which is painted to be point five value gray.

That has

a scale of point five so we see scattering there and then we see a lot of scattering

around the ears.

Which of course doesn't look realistic at all so we need to dial in that value

and mix it with a shift a color.

Rgb.

Art mix rgb node

and let's.

For the top.

Color swatch

i'm going to copy the scale value that i was happy with point zero three

have moreover it hit control c

and then click on the color swatch and for the value.

Let's paste that in there.

And then for the operation let's choose add

because it once i add the color from r.

S as a scale texture.

It will allow any areas that are black will add nothing to this value

so the majority of the head will stay at point.

Zero three

and then anything above zero will simply be added increasing the scale

allowing more light to scatter through it.

Like the ears which is what we want so let's plug in the color to

color swatch number two

and then plug the color into the scale value.

Giving us continued

surface effect all over the mash but it's much

more concentrated in the ears and the eyes.

So here's where we have the option to

adjust the factor

and dial in how much of that scattering that we want

so let's go way down let's go to point one.

And that's still too much how about point of two.

Erykah

you know that's a little bit better

and

certainly easy to dial in if we want more scattering in the ears which is.

You know something common that

people like to do.

Let's see here i wonder how we're looking with

our other.

Lighting scenarios.

Let's disable render a and take a look at render be.

Yeah that looks pretty good from that angle how bout.

C which is basically just a backlight

it's still looking good still looking subsurface scattering.

So that's.

Great I'll stick with.

Render be for a little while

i think that's my favorite.

Lighting setup

and jump back over the node editor.

Because the only component that's missing from my

simplistic subsurface.

Skin material

is the specular component.

So if we add a shader.

Glossy b sdf.

And then mix it

lets the shader mix shader node.

Mix it with our sub surface.

We'll start to get some reflections which are certainly a necessary part

of a skin shader.

And

i'm going to sound like a broken record but with reflections comes for now.

So let's create that component now.

Shift a input.

Layer weight.

Shift a vector er.

Let's see

not vector i'm sorry converter

color ramp.

Plug in our facing value into the factor of our color ramp.

And just to

let's see dial this in

let's plug it into an emission node first before using it.

To control the factor of our mich shader node.

There we go let's switch our interpolation to be spline and drag our lower.

Dark flag up.

Yeah to be like that

and now plug this into.

The color output into the factor value of our mix shader.

Plug that back into the surface.

So we can see our specular component now.

I think that's looking a whole lot better.

But.

I will i'd like to take this one step further

and also use this color rant to control the roughness value

of our glossy b sdf so that.

As our geometry faces away from the camera

which is increasing the amount of the glossy be sdf which is why we get this nice rim

light

i also want it to.

Decrease the roughness value making it

more shiny.

So let's add a color mix node.

And let's make the top

color swatch the value of the surface that's facing more directly at the camera.

Change that to point.

Three.

And then

for color swatch number two let's change that

to be

much lower to be more shiny

and let's try point o one for that.

Than the color of our color ramp goes into the factor.

And this color goes into the roughness.

And then let's do a test with and without at first without.

And and.

Oh

okay i messed up

i messed up something let's go back.

I also need another mix node like this one to control the factor.

A little bit more because

right now it's black.

You know for the faces that are.

For the surface it's facing the camera more direct early

so there's no reflection happening which is

clearly not.

Accurate

so we'll plug that color ramp into the factor of another mix node

and the top value

needs to be let's say point one and then the bottom value needs to be.

Point.

Let's go point five.

That might be a little bit strong in both areas let's go.

Point three in the bottom

and point

o five

in the top.

Yeah let's give that a shot.

There you go that's much better.

With the.

Glossy clearly showing up on the

front of the forehead front of the nose and also the lips.

That's certainly helping

our skin out.

That's without the roughness maps now it's jumped to slot six.

And plug in our mix node.

For our roughness value.

And render again.

And here we have a much.

More subtle glossy effect

but this is how we can control.

How sweaty our character is so if we go to slot seven.

You know he looks a little bit shiny or a little bit more sweaty slot six.

Not so much.

So we can tweak those values i think i i would tweak the values for.

Let's see the upper slot to be let's see point two five instead of three.

And then maybe increase the factor how much.

How much gloss is being added.

Right now the value is a point o five i would increase that

let's see I'll actually increase that two point one double it

and then leave the roughness as is

at point three.

And then perhaps bring in a little bit more reflection on the sides of the head.

With this bottom value over here from point three let's go to point

four.

Yeah i think that's pretty good.

Do one more render.

Jumping back to the.

U the image editor.

Let's put this in slot five.

Yeah i think i'm pretty happy with that.

Switching back to slot six.

Then slot five.

More reflections.

Or higher gloss value.

On top of the sub surface i think works good

what we want is a nice balance when it comes to skin

wear with subsurface.

The detail sales will be washed out basically that's how it should be

and the way we get them back is with

you know specular reflections it really gives you a sense of the depth that the light

is penetrating

so that's definitely a key part is striking the balance between specular

and subsurface.

But yeah that's you know essential really all of my

components for the simplistic subsurface shader using the.

Subsurface node

and if we go back to the node editor and.

You know i have

all kinds of places to plug another map in.

For example.

Let's add a bump map

shift control d

my image texture sure.

Go grab that.

Texture map

sss bump right here.

And to test this out

let's unplug our color from the subsurface scattering node and leave it.

A whoops that was the scale let's unplug the

color texture

so that it's white and at this point i need to do render previews

at a higher resolution to see more details

i'm going to bump that up from fifty percent

of the render rez two hundred per cent

and also increase my samples well.

No i won't do that quite yet i still want

you know.

Optimize renders for the previews

and

anyway so the bump map is going to be plugged directly into art displacement output

of our material

and.

How about we make a little bit more room over here.

Right away i know that my bump is going to be way too strong.

Or at least usually it is so let's try doing a render as is and see if we need to

dial the bumped down at all.

Okay it might be kind of hard to tell because.

It's still a fairly grainy render.

That's another thing about subsurface it needs more samples to clean up

and since my bump map is a basically poor detail

you can't tell the difference between pores and noise.

So

i also didn't render

a

before comparison so let me do that real quick before we start to

dial in

the

button math

jump to slot five.

And.

Disconnect the bump image texture.

Here we go here is before

four is after.

So.

There's quite a large change

and it's almost like the face sort of

mushers and melts a little bit once the bump is applied and that's because the bump

is way too strong.

So let's jump back to our note editor and add

a a.

Converter math node.

Where we can plug our bump texture into

here's where we can change our operation to multiply

and change the.

Multiplied value down here

to make it point one of the original intensity of the map.

Now let's plug that into our displacement

output.

And try rendering again.

Here we are with a.

Bump map added let's see if we can even tell a difference.

We can certainly see a shift but.

You

can't really distinguish the extra detail due to the noise

but you know this'll be really good when i.

Render my final.

High sample high resolute ocean

image

but

for demonstration purposes i'm really just showing you how i go about.

Dialing in these values

and now that i have the bump dialed in i can

reconnect my.

Color texture to the subsurface scattering node.

And then lastly if i want to be thorough i can

duplicate my image texture node and again shift control d.

And this will become my specular map.

Keep in mind all of these maps i showed you how to create in the realistic heads series

so

if you went through that you should already have a detailed head model

with detailed textures like this to accompany it that you can just plug directly into

cycles to get.

That updated.

Subsurface sea goodness

like we're doing here

i don't want you to think i'm just breezing through these textures and happen to have

all of them

you know it's a fairly involved process that you can see in the realistic heads

series but

anyway.

The last map I'll show you is the spec map.

And if we plug this into.

An emission no to see exactly what we're dealing with.

You can see that it's based on the color map with

that's been

converted to a black and white value map

and that we have some highlighted areas of white around the eyelids to.

Give us more of a a

wet

eyelid kind of look also in the.

Lip ps we want those to be a little bit more reflective due to their wetness

but then in general we just have a breakup.

Of the skin

speculating.

So we're going to plug this into a

let's see color mix rgb node.

And use the image as the factor

and then from there we will I'll choose colors that we want to be

are low value and are high value

for this top color swatch which will be.

The lowest value of speculating.

Let's make that.

Point three.

And then take it towards the blue direction

a little bit.

I like that.

Because when it comes to human skin it helps to take the specular reflections into

the blue spectrum just a little bit.

Let's

copy that color swatch now

with hovering over it and hit and control c then pacing it with control v over the

next color swatch

and let's take that value from point three all the way up to one.

And now we have that variation.

In the specular map but we have a little bit more control over it and we don't want

the lower value to be zero we still want it to reflect a little bit

but and.

I tend to make my my controlling maps be black and white because that's easier for me

to understand.

It maps

and also i'd see how easy it is to plug it into a mix note and dial in specific

values after the fact like here

in the shading network but anyway now that i have that setup

let's plug that into our glossy color.

And

that should help to break up.

Our glossy component of the sky when.

A very realistically because.

Before this it was very uniform across the entire.

Head

and breaking that up certainly will help with realism

so at this point i think i'm happy with my shader

based on the preview down here and i will.

Let's increase my samples for for a final render from

five hundred to one thousand

and hopefully be done with this simplistic.

Skin shader.

And at about six and a half minutes.

Which really isn't too bad.

Considering you know we're at a fairly high resolution and certainly a lot of samples.

And.

It's a pretty good.

Representation of skin i think but like everything it could of course use some more

tweaking

but at this point i'm fairly satisfied fide

and

i would begin to do test renders in different lighting conditions one thing that i

notice can affect a skin material.

More than

you might expect is the environment light.

So

let's switch to slot number three

and.

Enable.

My world environment texture which is key currently at a strength of zero so it's

basically turned off.

What if we switch set to number one

and it's.

Clearly way too strong so it's good to point five.

And this represents more of a daytime.

Rendering scenario

and while this looks pretty good and typically.

In environment lights once they are introduced.

I'll have to go back and re address my subsurface settings because it needs to look

good in both lighting conditions

but i suppose at this point i'm pretty satisfied with the simplistic version of the.

Skin shader

and i know i'm calling it simplistic but if we take a look at the node editor

so some might not call this simplistic because we have a lot of nodes in here

but that's mainly due to the textures that i'm using.

Because as far as sub-surface goes it's just one node.

One layer if you will.

It's very common when it comes to skin shaders to have a tri layer system which i

went over with blender internal

in the realistic head series

and if you come from mental ray or v ray or other high end render engines.

You'll be familiar with the tri layer system

that's where it can get really complex and

in blender again Matthew heimlich has

ported Arnold's

complex shader.

Into blender as a node group and that's what i'm going to show you next but.

If you feel satisfied with the result that i'm kind of showing you and feel satisfied

with the

range of options that you have to tweak

just the subsurface scattering node by itself

then this is.

A good option for you it's what i tend to do.

Namely because i'm satisfied with the rest salt and this next method the complex.

Arnold port shader

takes almost twice the amount of time to render and clean up

but it does give you all those options that you're used to if you come from one of

those commercial render engines.

So that is what the next lesson is about.