Materials - Blender Master Class: A Hands-on Guide to Modeling, Sculpting, Materials, and Rendering - page 187

so the grain will be aligned with the v -axis in
UV space. In other words, it will be aligned
vertically in the UV Image editor, so ensure
you have unwrapped the object appropri-
ately when enabling this option.

Cubic Interpolation This alters how the sur-
face blends between light and shadow, usu-
ally with smoother-looking results though
often slightly darker.

Transparency Turn on the Transparency check-
box to render a material with transparency. This
panel offers three ways to render transparent
objects, using the surface's alpha value. The
simplest, Mask , simply blends the material into
the background where the color is transparent.
Z Transparency is slightly more sophisticated,
rendering whatever is behind the transparent
object. Ray-traced Transparency calculates proper
refraction. Choosing Ray-traced Transparency
brings up a variety of options that allow you to
set the index of refraction of the material and
the glossiness and amount of filtering done
by the material.

Figure 12-6: Different levels of hardness affect the
look of specular reflections. This checkerboard tex-
ture is used to control the hardness. (You could also
vary hardness using a texture map.)

Cycles Materials
Unlike the Blender Internal renderer, which is
packed with dirty tricks and approximations to
make rendering quicker, the Cycles renderer uses
more physically realistic models for materials. It
combines realism with a node-based approach that
focuses on building up complex materials from
simple parts. You can still use the Materials tab
of the Properties editor to edit Cycles materials,
which gives an overview of the current material,
but it's much simpler and clearer to use Blender's
Node editor, as shown in Figure 12-7.
To create a material with Cycles, all you need
is a Shader node and Material Output node. You
can build out from there and combine other shad-
ers, inputs, and textures to create a wide variety of
materials. To add a node, use shift -A and choose
the node you want from the menu that appears,
just like adding objects in the 3D viewport.
The BSDF (Bidirectional Scattering Distribution
Function) Shader nodes control how materials
work. These functions define how light interacts
with a surface—for example, whether the material
reflects light in a diffuse way, acts as a mirror, or
transmits light like glass. You'll find the BSDF shad-
ers under Shaders in the Add menu in the header,
along with a few other options.

Mirror Enable Mirror to turn on rendering ray-
traced reflections. The settings in this panel let
you define the amount ( (Reflectivity) ) and sharp-
ness ( Glossy Amount ) of ray-traced reflections.

Subsurface Scattering (SSS) This option controls
the effect of light scattering under the surface of
a material commonly found in skin or wax. I'll
discuss this in more detail in “Subsurface Scat-
tering” on page 194.

Options This panel contains some miscellaneous
options. For example, the Tracea bl e setting
controls whether an object is taken into account
when rendering ray-traced shadows and reflec-
tions. I'll cover these when they come up, and
you can look up any I don't mention on the
Blender wiki (at http://wiki.blender.org/ ).

Shadow This panel controls how an object receives
and casts shadows. For example, the Cast Only
option makes an object appear invisible except
for any shadows it casts. Shadows Only renders
a material's shadows as the only nontranspar-
ent parts. (This is particularly good for creat-
ing shadows that you can then composite into
another image.)