Original subtitles

Welcome to another Blender Cookie tutorial.

My name is Kent Tramel and in this video

we're going to be taking another look at

realistic skin shading with Blender. So far.

we've 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 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 sees 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 photographs 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. Okay 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 orangish 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 subsurface causes

a softening of the shadows and therefore

softening of the skin detail and as far

as the orangish red color that's 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 years ago. It's a

slightly stylized 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 poor 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 map, specular maps,

all the textures that I would need for a

realistic skin shader I've already created. It just needs to be plugged into

a shader appropriately. So before we actually create the shaders let's go

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 hit zero. There we 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

Ren A which is my first lighting scenario. Pretty standard stuff with a.

strong key light, a back/rim light and

then a large card which acts as a sort of

global rim light that will show up particularly well with reflections and.

then let's go to the next one Ren B. This is actually very similar except I

would change the world value. So let me

go choose an environment map. I will of

course include some environment maps

in the source files and okay so if I bump

this up to let's say 0.5 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 C which if I let's see turn off

my environment light again this setup is

useful for looking at how backscattering works through the ears and if my

subsurface 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. I'll switch my 3D viewport to the node editor with the

in 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_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 subsurface scattering

specifically for skin with matte Heimlich's

port 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 V-ray

mental ray or obviously Arnold but being

more complex means that it actually renders 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 BSDF and plug in the

BSSRDF 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

to point one and you'll see that less light is able to make it all the way

through the object and our shadows appear and if we go down a little bit

more let's go to point oh 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 about a point oh 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 at 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 Gaussian cubic is a

sharper fall off based on the documentation

and it actually renders a little bit faster but then Gaussian 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 I'm going to select that it is the default or it

should be and below that we have color and this is the general color of our

object so if we let's see switch that

to 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 jump down we've already addressed 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 shadows and with skin it happens to be

red so if we open up those options we have three values with 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 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 and 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 red and I think I want it to be a little bit more.

orange let's remove the green color to saturation all the way down to zero

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 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 orange is 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 well 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 brighter so 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 below

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 for example if we

used a photograph to create our textures

it's already blurred there's already

blurring happening within the subsurface

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 Gaussian 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 for the subsurface scattering node and we're ready to plug

in our texture 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

and first we're going to load our general head color texture let's enable

thumbnail 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 UV 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 let's see color RGB curves

node 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.

there we go 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 scale and SS

scale B 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 the lips

which is you know if you want to control

the scale that's where you're going to

want to control it so that one's 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 okay so now if we plug

this directly 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 0.5 value gray that has a scale of 0.5 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 I'm sorry

mix RGB node and let's for the top color

swatch I'm going to copy the scale value

that I was happy with 0.03 hover over 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 our SSS scale texture it will any areas that are

black will add nothing to this value

so the majority of the head will stay at

0.03 and then anything above 0 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 2 and then plug the color into

the scale value giving us continued subsurface effect all over the mesh 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 0.1

and that's still too much how about 0.02.

there we go you know that's a little

bit better 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 b yeah that

looks pretty good from that angle how about

c which is basically just a backlight.

it's still looking good still looking

subsurface scattering so that's you know

great I'll stick with render b for a little while I think that's my favorite

lighting setup and jump back over to

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 bsdf and then mix it let's see

shader mix shader node mix it with our subsurface we'll start to get some

reflections which are certainly a necessary part of a skin shader and I'm

gonna 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 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 mix shader.

node there we go let's switch our interpolation to b 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 would like to take this one step

further and also use this color ramp to

control the roughness value of our glossy bsdf so that as our geometry

faces away from the camera which is increasing the amount of the glossy bsdf

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

let's 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 0 1 for that.

then 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 it first without 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 that's facing the camera

more directly 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

oh five in the top yeah let's give that a

shot there we 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 map now let's jump 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

shinier a little bit more sweaty slot

six you know not so much so we can tweak

those values I think 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 0.05 I would

increase that let's see I'll actually

increase that to 0.1 double it and then

leave the roughness as is at 0.3 and then perhaps bring in a little bit more

reflection on the sides of the head

with this bottom value over here from 0.3

let's go to 0.4 yeah I think that looks

pretty good do one more render jumping

back to the UV 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 subsurface I think works good what we want

is a nice balance when it comes to skin

where with subsurface the details 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 essentially all

of my components for this simplistic subsurface shader using the subsurface

node and if we go back to the node editor 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 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 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 so I'm gonna bump that up from 50% of the render res to

100% and also increase my samples well

no I won't do that quite yet I still want

you know optimized renders for the previews and anyway so the bump map is

going to be plugged directly into our

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 bump 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 bump

map jump to slot 5 and disconnect the bump

image texture here we go here is before 4 is after so there's quite a large

change and it's almost like the face sort of mushes 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 node editor and

add a converter math node where we can

plug our bump texture into here is 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 know can't really distinguish

the extra detail due to the noise but

you know this will be really good when I

render my final high sample high resolution 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 again

shift control D and this will become my

specular map keep in mind all these maps I showed you how to create in the

realistic head 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 subsurfacey 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 head series but anyway the last map I'll

show you is the spec map and if we plug

this into an emission node 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 we have some

highlighted areas of white around the

eyelids to give us more of a wet eyelid

kind of look also in the lips 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

specularity 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 choose colors that we

want to be our low value and our high value for this top color swatch which

will be the lowest value of specularity let's make that 0.3 and then take it

towards the blue direction a little bit

about 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 0.3 all the way up to 1 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 0

we still want it to reflect a little bit

but I tend to make my my controlling maps be black and white because that's

easier for me to understand as I make

the maps and also I 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 set up let's plug that

into our glossy color and that should

help to break up our glossy component of

the skin 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 a final render from 500 to 1000 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 you know 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 and I would begin to do

test renders in different lighting conditions one thing that I noticed 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 currently at a strength of zero so it's basically turned off what if we

switch that to number one and it's clearly way too strong so let's go to

point five and this represents more of

a daytime rendering scenario and while

this looks pretty good typically environment lights once they are

introduced you know I'll have to go

back and readdress 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

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 subsurface

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 you know a

good option for you it's what I tend to

do namely because I'm satisfied with the

result 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.