CG Basics - An Introduction to Computer Graphics for Artists - page 25

Fig. 2.19 On left , a ray is refl ected or not depending on the direction of normals. On right , a refl ection
is inside-out because normals are facing in, rather than out

Fig. 2.20 A geometry node chart where the child nodes are geometry and the group node is a
container for the geometry

wanted each of them to behave differently at the same time as they moved together,
you might connect all three to a single node, then manipulate each object separately.
This would allow them to move individually and together at the same time. Sometimes,
nodes are used to organize changes that are made to geometry, so that they can be
adjusted separately. These changes are called transforms (Fig. 2.20 ).

2.4.2 CG Attributes

2.4.2.1 Introduction

A polygon always has attributes that affect the way it looks when rendered, even if
you don't assign any to it. These are default values. A default value is used in the
absence of any other input. For instance, when a cube is made, it has to have a certain
size. If you don't specify a size, it will use a default value instead. This is often 1 or
10 units. To render an object, it must have material attributes. These tell the renderer
how the polygon reacts to light.