Graphics Reference
In-Depth Information
textures for the bottle: opaque, reflective, and transparent. You will explore several possibilities for each of
these categories so you will be able to have a good general idea of how to create a wide variety of surfaces.
Opaque Materials
At face value, opaque materials seem very simple. After all, they lack transparency and reflections for the
most part. Although many opaque surfaces can be easily constructed, there are a lot of things to take into ac-
count to make them look really good at render time. As you may recall from a previous chapter, all colored
materials are reflective. The color of an object is determined by the color wavelengths that are reflected.
Any visible object in the real world is reflective to some extent. The lack of mirrorlike reflections is simply
due to the microscopic roughness of the surface. As the surface of an object becomes more perpendicular
to our point of view, the reflective areas appear to get closer together because of the perspective, and the
amount of reflection appears to increase. Because of this, many materials that would be typically thought of
as nonreflective can benefit greatly from some amount of reflection and, specifically, Fresnel reflection.
In
Figure 6-24
, the bottle has a simple color applied. The look is relatively flat and basic. The material
does nothing to accentuate the form of the model and really doesn't feel like it is a part of the scene.
To help this, add some Fresnel reflection and turn on Blurry Reflection. To keep the effect subtle, a lower
Fresnel amount as well as a higher Roughness setting can be employed. Roughness controls the amount of
blur in the reflections. Think of this as the microscopic roughness on a surface; the higher the setting, the
less mirrorlike the reflections become. Another way to soften these reflections is to control the reflective
color. Do this by setting the Reflection Color value (or Specular Color if you are using the Match Specular
setting) to the same as the Diffuse Color value, or to a slightly lighter version of the same color. The closer
the reflected color is to the diffuse, the softer the reflections will appear.
Figure 6-25
shows the effect of 50%
Fresnel with Blurry Reflection, Roughness set to 100%, and Specular Color (along with Reflection Color)
set to the same as Diffuse Color.
In addition to reflections, the color of many objects shifts as the surface angles away from viewer. As the
reflection amount increases (because of the Fresnel effect), the diffuse amount decreases. Remapped (shif-
ted) colors can be achieved with a gradient layer (this is also called a
ramp
in some other programs). With
a gradient in this case, you can alter the effect of the diffuse amount. This material has the default of 80%
set for Diffuse Amount. With Fresnel set to 50%, that means you can subtract that amount from the diffuse
amount as the incidence angle approaches perpendicular. To set up the gradient layer you will need to do the
following:
1.
Add a gradient layer, set Input Parameter to Incidence, and change the layer effect to Diffuse
Amount.
Figure 6-24:
A basic opaque material with no adjusted settings
