Graphics Programs Reference
In-Depth Information
Chapter 1. Overview
of
Materials
in
Cycles
In this chapter, we will cover:
• Material nodes in Cycles
• Procedural textures in Cycles
• How to set the World material
• Creating a mesh-light material
• Using displacement (aka bump)
Introduction
Cycles materials work in a totally different way than in Blender Internal.
In Blender Internal, you can build a material by choosing a diffuse and a specular
shader from the Material window, by setting several surface options, and then by as-
signing textures (both procedurals or image maps as well) in the provided slots—all
these steps make one complete material. After this, it's possible to combine two or
more of these materials by a network of nodes, thereby obtaining a lot more flexibil-
ity in a shader's creation. But, the materials themselves are just the same you used
to set through the Material window, that is, shaders made for a scan-line rendering
engine as Blender Internal is, and their result is actually just an approximation of a
simulated light absorption-reflection surface behavior.
In Cycles the approach is quite different: all the names of the closures describing
surface properties have a Bidirectional Scattering Distribution Function ( BSDF ),
which is a general mathematical function that describes the way in which the light is
scattered by a surface in the real world. It's also the formula that a path tracer such as
Cycles uses to calculate the rendering of an object in a virtual environment. Basically,
light rays are shot from the camera, they bounce on the objects in the scene and keep
on bouncing until they reach a light source or an "empty" background. For this reason,
a pure path tracer such as Cycles can render in reasonable times an object set in an
open environment, while instead the rendering times increase a lot for closed spaces.
For example, furniture set inside a room, and this is just because the light rays can
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