Rendering the Enforcer - ZBrush Creature Design: Creating Dynamic Concept Imagery for Film and Games - page 653

ZBrush materials are composed of one or more “shaders,” which are layered on top of each other. The in-
terface itself lists the shaders from left to right. The shader mixer is used to determine how the shaders are
blended together. It can get confusing really fast, so I like to try to work on each component of the material
individually to establish the basic properties and then spend some time blending them together.
One of the oddest quirks about materials in Zbrush is that you never create a material from scratch; in-
stead you edit an existing material and then save it under a new name. The same goes for the shaders that
make up the material. So there's no “new material” or “new shader” button. You start with a material that has
the number of shaders that you need, and then you copy other shaders into the shader slot and then tweak as
needed. It is an odd way to work and if you're already confused, don't stress out. Going through the process
a few times will make it a bit clearer. It's always best to break it down into its simplest components.
To create a believable skin material, we need three basic elements. I like to separate each of these ele-
ments into its own shader and then combine these shaders into a single three-shader material. The shaders
we'll need to achieve this are:
A Diffuse Shader This determines how the light is scattered as it is reflected off of the very surface of
the skin. This shader is responsible for the overall color when combined with the polypainting. I imagine
what dry skin would look like and then create a shader to simulate this look. We'll use the basic shader
to handle the diffuse shading.
A Specular Shader This determines how the skin reflects all of the light sources in the scene—in other
words, the shiny quality of the skin. This is layered on top of the diffuse shader and is responsible for
giving the skin a wet or oily quality. We'll use a standard shader to create the specular quality.
A Subsurface Scattering Shader This shader simulates the luminescent quality of the skin. As photons
of light penetrate the layers of skin they bounce around, pick up the color of the deeper layers of tissue,
and then exit the skin giving it a kind of glow. This helps make the model look as though it is made up
of living flesh. In many 3-D packages, this effect is simulated by more or less replicating the physical
properties of light. In ZBrush, the effect is done using a gradient of colors—this is a cheat, but it's an
effective one!
Create the Diffuse Shader
The diffuse shading is pretty straightforward. Using the Basic shader combined with the controls in the
LightCap editor, you'll create the overall surface quality of the skin. Diffuse shading simulates what hap-
pens when photons of light are reflected off of a rough surface. The tiny bumps on the surface cause the light
to be “diffused” back into the environment, in other words, they bounce off of the surface in all directions.
Think of sunlight reflected off of concrete. Skin is not as rough as concrete but you can imagine that by
adjusting the settings you can give the viewer some sense of the creature's character.
1. Continue with the project from the previous section.
2. Set the subdivision of the creature's body to 7 and turn on the paintbrush icon in the SubTool palette
to activate polyPainting. The colors of the skin appear on the surface but you'll also notice that a material
has been painted on the creature. Until you remove this material, you won't be able to see your new cus-
tom materials update as you work.
3. In the Material palette, select the Flat Color material. On the top shelf, press the M button. In the Color
palette press the Fill Object button ( Figure 10-9 ) .
Figure 10-9: Fill the surface with the Flat shader to remove any materials that have been painted onto the
model.