Concepts of Computer Graphics/Introduction

This Wikibook is concerned with explaining the concepts of computer graphics to a non-technical audience. Most books on computer graphics are written from the perspective of a programmer who is attempting to complete an implementation of some algorithms, be they a computer game, a ray-tracer, or an animation system.

In contrast, this Wikibook seeks to explain the concepts of computer graphics to someone who has no intention of implementing anything and only a basic level of math knowledge (and patience). Such a reader might be an artist who seeks to better understand the systems he uses to produce his art or video game content, someone who is attempting to get started in computer graphics but has no previous experience, or perhaps just a curious person who would like to know more about the graphics that increasingly make up the media we experience.

Since we are starting at the very beginning, our first step will be to define the problem that the techniques of computer graphics attempt to solve. So to begin our discussion, we shall make a first (clumsy) attempt at explaining the problem by saying that the main problem in computer graphics is how to create a desired image.

Given the number of different reasons people want to create images, a statement that encompasses all of computer graphics must necessarily be vague. In order to give a better sense of what we are trying to understand, we'll discuss some specific problems that computer graphics attempts to solve.

One of the most common uses for computer graphics is the creation of an image that looks like a photograph from real life, but portrays something we could not actually take a picture of. For example, we might want to create an animation for a movie that portrays an alien creature or location, or we might want to create an architectural rendering to get an idea of what the final building will look like. We'll call this type of computer graphics photo-realistic. Typically there is a significant amount of time available for creating these images, and so the techniques often attempt to capture the properties of lights and surfaces as accurately as possible, at the expense of time needed to compute the image.

Another common use for computer graphics is the creation of images very quickly so that they can be used in an interactive animation; the application of these algorithms that most people are familiar with is computer games. As a user controls their character, we want to create a series of images very quickly (hopefully 30 per second or more) that respond to their inputs. We'll refer to this type of computer graphics as real-time, or interactive. We might want these images to look as realistic as possible, but the fact of the situation is that if we have more time to devote to computation, we can create better results. Thus, real-time computer graphics is usually concerned with techniques for creating the best-looking picture possible with the very short amount of time available between frames.

There are many other applications for computer graphics as well. We might be interested in automating a complex picture that we could make by hand for convenience, or we might be interested in creating an image that is abstract or random in nature. In fact, there are many applications of computer graphics that fall somewhere in-between the two extremes presented above, such as medical imaging and visualization systems. However, for an introductory text, it will suffice to present the two main techniques that are mixed and matched for the desired results in practice.

In the text that follows, we'll begin by attempting to understand the concepts of pixels and how computer represent color, which is the format for what computer graphics algorithms output. After that, we'll consider how we represent the input data that programs in computer graphics use, the 3D objects that get rendered. With these basics out of the way, we'll then delve into the techniques of photo-realistic and real-time rendering.