Graphics Reference
In-Depth Information
CHAPTER 8
Color
8.1
Introduction
This chapter covers some rudimentary facts about color and its role in computer
graphics. Describing what one needs to know for a basic modeling system is not that
hard. This is the main goal of this chapter, but we shall also sketch a more complete
view of what color is all about. The reader who is unfamiliar with color and the issues
surrounding it should be warned, however, that it is very easy to get confused in the
terminology and what it really means because this is a big topic and the discussion
here is extremely brief. A lot of terms having to do with the psychology of color do
not have precise meanings (in fact, there is no universal agreement on some of them)
and a real understanding comes only after extensive experience. For the reader who
wants to learn more, a good general reference for color is [AgoG87]. Hall's topic
[Hall89] is a good place to look for computer graphics applications and [Roge98] is
another.
The first three sections will cover general topics dealing with color. The last two
discuss the main practical facts one needs to know in order to use color in a model-
ing program.
8.2
What Is Color?
What is color? This may seem like a silly question, but there are some common mis-
conceptions, such as:
(1) Color is a property of materials (as in the case of a red dress).
(2) Color is a property of light (as in the case of a red traffic light).
Color is none of these, that is, there is, for example, no generic entity called “light” to
which the property of “red” is added to get “red light.” The fact is that under differ-
ent lighting conditions, colors change. Newton already knew that light rays are not
colored. Although the question about color is an old question, real progress has only
