A Guide To - Skin Material With ZBrush and Single Pass BPR - PabloMunozG
A Guide To - Skin Material With ZBrush and Single Pass BPR - PabloMunozG
A Guide To - Skin Material With ZBrush and Single Pass BPR - PabloMunozG
a guide to
skin material
in zbrush &
single pass bpr
BONUS
repurposing
the SKIN MTL
for rendering
creatures
www.pablander.com
Including
resources
Introduction
I know I have kept you waiting for this tutorial for a while
but I took my time because I wanted to give you guys a
quality tutorial that you can easily follow.
Like my previous two eBooks: Creating dreadlocks with
fibermesh and Wet Clay material; this new tutorial is also
for an intermediate level user. However I do go over
some main things in detail and if you are an experienced
user you can follow the highlighted words and phrases that alone should give you a good understanding of my
workflow.
Lets get started!
Research
I didnt want to bore you too much with the research
behind this tutorial so I decided to filter the information
into what I consider to be the most relevant bits.
Dry:
Thin
almost invisible pores
Dull and rough
prompt to crack and peel... more wrinkles
Skin types
I have used many skin types in this project as well as
making new skin types by mixing several of the ones I
have made. For practical purposes, I will mention the
two fundamental types: dry and oily.
When working in ZBrush I used to think that dry skin
needed a diffuse shader and for the oily skin I could
just throw a specular shader on top to make it shiny.
Well, in some cases that simple approach could work but
it wont get very realistic results, there are a few other
differences between these types of skin, apart from the
specularity.
Oily skin is thick, usually has visible large pores and
is often regarded as bad skin because of an excessive
production of sebum (natural skin lubricant), which
causes shininess and pimples. Oily skin is also less
prompt to wrinkles.
Dry skin usually looks tight and is prompt to crack
and peel due to a lack of sebum (lubricant). It also has
a slower cellular renewal process which means that the
cells do not repair as fast, making the epidermis thinner
(more on this later). Also, you can see reddish spots
more clearly.
The above descriptions are concise but the main things
we need to know from each type are:
Oily:
Thick
large pores
shiny
less wrinkles
www.pablander.com
Skin Layers
Chances are you have probably used or heard about
Skin pigmentation
These three maps helped me to create something like
this:
Knowing this is
very useful and
when implemented
correctly, it give
amazing results.
The way that
ZBrush does SSS
is a bit differently
though, so lets see
if I can explain how
SSS works a bit
better:
First lets get
the meaning of
SSS out of the
way. SSS stands
for Sub-Surface
Scattering, and
www.pablander.com
www.pablander.com
Creating the
Skin Material
You are probably familiar with this but lets take a look
at it anyway to understand how this works could help
you enhance the effect of realistic skin with the BPR
single pass.
With all the testing that I have done with MatCaps and
Standard Materials I realised that in most cases (and
also depending on what effect you are after), when you
tweaked a MatCap to the point you are happy with and
then you added a colour or texture map, the result was
somehow inconsistent. With a standard material, on the
contrary, if a colourless model looks good with just the
material, when a polypaint layer or texture is applied the
render, will look much better!
www.pablander.com
www.pablander.com
www.pablander.com
Lets try to keep things as simple as possible, so the last thing I changed for the diffuse
shader was the specular: I gave it 2 points in the specular slider and tweaked the curve to
be smoother:
I also like the specular colour to always be white. To do this, I changed the colorise
specular slider to be 100 and selected white for the specular colour. Finally, I added a bit
to the high dynamic range modifier.
You might notice that the model looks overexposed, almost as white as it was when you first
applied the Quadshader. Dont panic, this is intentional, turn on the polypaint by clicking
on Colorise. Youll see that the texture looks OK on the model. Leave it on for now, and
we just need to tweak a couple more of sliders that Ive found to be very useful, but are
not that popular.
They are the Anisotropic Diffuse and the Anisotropic Specular, you can easily achieve the same velvet effect
I mentioned earlier by changing this attribute because what it does, is shift the effect of the diffuse (or specular)
shaderacrossthe model. So, 0 means there is no effect and 100 means iscompletelyinverted, I left the
Anisotropic Diffuse at 0.28 and the Anisotropic Specular at 0.19.
www.pablander.com
type and oily skin type (this way you can save a generic material that is easier to tweak depending on the nature of
your future projects).
The specular or shininess of the skin is achieve by adding a specular shader to our current material, which so
far has the diffuse shader we just built and 3 more generic shaders. First, lets set up the model so we can easily
judge the contribution of the specular by itself... Turn off polypaint, turn off the diffuse shader (click on the little
dot from the slot 1 of the material) and turn on the shader 3. The shader 3 will be the specular we are going to keep
shader 4 for the SSS contributions and shader 2 for an extra cool effect.
So you should have something like this again:
From this shader we are only interested in the specular. Go ahead and slide the ambient and diffuse attributes
down to 0.
www.pablander.com
more trick I would like to share with you, and its again
using the Anisotropic Specular slider.
OK, last but not least, we need to define the way our
specular shader is going to interact with the previously
created diffuse shader.
www.pablander.com
10
www.pablander.com
I would say that here we finish with the basic part of the
tutorial and we are ready to move on to the advanced
second part of building a skin material for BPR in a
single pass.
11
www.pablander.com
12
The next two sliders, Inner Blend and Outer Blend are
actually the attributes of this shader that I prefer to use.
The Inner Blend uses the same principle of the facing
ratio but it blends the colour set in the InnerBlend picker,
so if you move the slider to 1 youll see the effect:
www.pablander.com
13
Once you have done that, try BPR again and see if you
finally start to get excited about this process.
OK, lets put the outer blend slider to 1 and all the rest
of the sliders back to 0, including the Fresnel effect. Hit
the BPR button. You should get something that looks like
this:
www.pablander.com
Now that we have the SSS effect working for us, we can
start tweaking the settings from the render palette. What
I usually do, is create a document in Photoshop and
paste screenshots of the renders, so that every time I
do something different in the settings I can check and
compare the changes. I will guide you through what I
have found to be the best settings for this particular
project, so you dont have to do any of that.
From the render palette, expand
the sub-palette called BPR
SSS. The first thing you see, is
a button that says SSS Across
Subtools, click on it to enable
it. This button determines how
ZBrush will light up the subtools
14
Obviously, 100 rays look much better than 30, but usually
you dont really need more than 50 rays. However, for
the purpose of this tutorial, I will leave it set at 100 for
best results (youll see why after reading the next couple
of paragraphs).
The Angle will affect how narrow the SSS effect is,
based on the light source, the way I understand it, is that
the value you set in the Angle slider will determine how
much the SSS effect will spread around the model,
taking into account the light position. For example, in
these images, I set the Angle to 1 and to 360, and I
moved the light source to the right.
www.pablander.com
15
OK, so lets see how this was done using the mixer for
this SSS shader. Open up the Mixer sub-palette and
for this shader we are going to concentrate on only 2
attributes (that is all we need): The S Exp and blending
mode.
To sum up, these are the best values I found to work for
what I want toachieve:
www.pablander.com
16
www.pablander.com
17
www.pablander.com
Cool, you can see how the lights (red dots) you placed
in the LightCap sub-palette are then translated to the
scene, very closely to how they look in the black box. At
this point, we are going to turn everything ON again,
because now we need to judge how everything is
going to look as a whole, not simply individually. So
turn the SSS back ON from render properties as well as
the primary light properties.
From the LightCap sub-palette, once you create a light,
you will get its attributes below the black box. Create
another light byclickingnew Light again and move this
one to the right (you can use the Light Index to select
and navigate between the lights).
18
Hopefully you can now see some of the effect of the Skin
Material working nicely with the light setup. The next
thing I want to do is get rid of those strong shadows
coming from the KEY light and make them more
diffused. That is achievedthroughthe render settings.
For this reason, I like to treatLightingand rendering as
one section.
Open up the render palette and we are going to tweak
the BPR shadow:
www.pablander.com
19
the material creation which is theenvironmentsub-palette. The reason I avoided it was because it is more relevant
now that we are dealing with rendering settings and also, because it is awesome! So simple, but so powerful. Let me
explain:
Environment Sub-Palette
In the same way each individual shader we created has options in the mixer sub-palette, they also have an area
called Environment that has 3 simple options: Shadow, Ao and vibrant shadows and AO. These attributes are
unique to each shader and the Shadow and Ao slider refer to the strength of those features for each shader. Maybe
an image will illustrate better what I mean. Here are the 4 renders - I switched the Shadow slider to 0 for each one of
the shaders that make up our skin material:
Perhaps the image above gave you a better idea, but if not, I want to explain this in a different way BECAUSE I
really want you to understand theseEnvironmentsettings. If you didnt know about it, this is probably the best TIP
you will get out of this tutorial. Im serious! It blew my mind when I found out about it. It will slightly change the
final look of your renders but you willdefinitelysee the difference in many ways.
TIP: Each one of the shaders we created have different properties and different ways that they mix with each
other in order to create the Skin material, but they all react to the light in the same way (to some extent). The
Environment sub-palette allows you to change the intensity of the shadows for each shader that make up the material
INDIVIDUALLY. The reason I think this is very powerful, is because it lets you mask out or lower the influence of
the SSS shader shadows, for example. I can still get the shadows I need but wherever the effect of the SSS is, the
shadows will be less prominent, enhancing the overall look of the render.
Take a look at how it works with practical examples, for image A, I took our KEY light and placed it
behind the model and left all shader environment shadows at 100. For image B, I simply changed
theenvironmentshadows of the specular to a lower number (83) and the SSS shader to 0 nothing else:
So you see how different the renders are and how much more realistic the image B is. In the same way you can
change the Ao (ambient occlusion if its enabled from render settings) slider, to affect each material.
www.pablander.com
20
From the render, I can see 3 things that are not quite
right:
The next sliders are Rays and Angle which work in
the same way as the counterparts from the BPR SSS
sub-palette previously discussed so I wont get into the
details here. Just a quick tip: when you set the Angle
to a high value, you should then increase the number
of rays too in order to
retain a good quality
render. In this tutorial, I
have set the Rays to 60 (I
will change this value to
120 for final render). An
angle of 90 seemed to
work well to achieve the
look I was going for.
www.pablander.com
21
Render
At this point I will edit the size of the document to
get a larger image. Go to Document, and change the
I think it looks much better now,rememberthat when
dealing with materials, subtlety is key. Finally, before
getting into compositing with ZBrush I like to move my
lightaroundand make various renders to test the
consistency of the material:
www.pablander.com
22
Filters
If you are familiar with Photoshop, filters in ZBrush,
are like the different adjustments you can find in
Photoshop. One of my mentors once told me that
masking is the backbone of the technical aspects of
compositing and through my experience, I have to say
that knowing this has helped me a lot. In Photoshop
you can bring all your passes, start masking things OUT
and blending all the layers to create your final image. In
my opinion, the power of using filters inside ZBrush,
relies on the capability of masking the effect of the
filter by a wide range of attributes without having to
create a mask or extra stuff.
Lets start by opening the filters Sub-Palette within the
render palette. The filters selection and switches
(to turn them ON and OFF) are identical to the way
we selected the shaders in the Skin Material and by
default they are all OFF so lets turn the first filer ON
My filters workflow
I like to start in order, thats why I enabled the F1 and
turn more filters ON as I go.
Asopposedto what I did with the Skin Material set
up, where all shaders were turned OFF (except for the
one I was tweaking), I like to see how the filters work
together.
The first filter is the noise effect, when you turn it OFF
you see the effectimmediately, that is another great
thing, you dont have to re-renderevery timeyou adjust
a filter.
The whole filter sub-palette
looks a bit overwhelming at
first because of the number
of sliders it has, but once
you get the hang of it, the
level of control it provides,
is fantastic. I wont explain
every single filter but Im
sure that with a general
guide on how they work,
you can figure out the rest
for yourself. I divided this
sub-palette in 2 sections
to easily digest what the
attributes are for. The
sections are Filters A and
Filters B.
Section A contains:
www.pablander.com
23
You can see the effect very well, but what I want now
is to only to sharpen the areas that are closer to
the camera. Here is where the masking I mentioned
before, starts to shine. Change the Depth slider
tosomethinglike 0.2. Basically, what we are doing is
telling ZBrush to apply the Sharpen filter based on
the depth pass, sothe positivevalues will sharpen
areas closer to the camera and the negative values will
sharpen the parts of the model furthest from the camera.
Recap:
1. Turn on the filter slot F#.
2. Select the type of filter you want.
3. Set strength and opacity to 100 andRadiusto
ahighernumber than 1 to see the effect of the filter.
4. Use the rest of the sliders to decide where and how
the effect is applied.
www.pablander.com
24
The adjustments
www.pablander.com
25
Conclusion
So the tutorial has ended up being quite long and it took
me a while to put everything together, but hopefully it will
give you a good insight into my workflow. It isnt perfect
or the only one by any means. If you are able to take
something away from this, even just a tip to improve your
art or speed up your process, then the time I put into this
is well worth it.
I know we are all super excited about the upcoming
ZBrush - Keyshot integration and that will supercharge
all of our renders. However, I still think that ZBrush can
produce amazing things as it is right now. This tutorial
was never intended to replace a more elaborate work
flow to produce higher quality images, but rather to
provide you with the option to obtain multiple variations
to choose from, without having to take your passes to an
external editing package, and to do this within very short
period of time (once you set everything up).
Keep in mind thatevery timeyou do a
BestPreviewRender, the individual passes are also
being created. So if you want, you can take your quick
render to Photoshop for further improvements, using the
passes that ZBrush generates.
Final Thoughts
I really enjoyed creating the material and the setup
as much as I likedwriting the tutorial. I tried to keep
everything very informal and casual because I write
based on my notes that I take as I progress on my
projects. However, if at some point you would like
to know more about something in particular or need
any help, feel free to contact me by email or on my
Facebook page, if I can I will always be happy to help.
www.pablander.com
26
Bonus Material
As I promised here is an extra bit of tutorial where I show you how easy is to modified the material to suit other
needs.
I will be using an alien head which is just a quick Dynamesh sketch with polypaint and I will show you how I
created this:
www.pablander.com
27
For the specular shader the render looked like this for
this creature.
www.pablander.com
28
www.pablander.com
29