Graphics Reference
In-Depth Information
features like physical simulation, artificial intelligence for characters, and systems
for adapting display quality to maintain frame-rates.
A range of software systems are available to assist graphics programs, from
simple APIs that give fairly direct access to the hardware all the way to more
complex systems that handle all interaction, display refresh, and model represen-
tation. These can reasonably be called “graphics platforms,” a term we've been
using somewhat vaguely until now. The variety of systems and their features are
the subject of Chapter 16.
A Brief Overview
When you want to go from models of reality to the creation, in the user's mind, of
the illusion of seeing something in particular, you have to have the following:
• An understanding of the physics of light
• A model for the materials with which light interacts, and for the process of
interaction
• A model for the way we capture light (with either a real or a virtual camera,
or with the human eye) to create an image
• An understanding of how modern display technology produces light
• An understanding of the human visual system and how it perceives incom-
ing light
• And an understanding of a substantial amount of mathematics used in the
description of many of these things
The difficulty with a bottom-up approach to this material is that you have
to learn a great deal before you make your first picture; many reasonable stu-
dents will ask, “Why don't I just grab something from the Web, run it, and then
start tinkering until I get what I want?” (The answer is “You can do that, but it
will probably take longer for you to get to the end result than if you try to have
some understanding first.”) As authors, we have to contend with this tension. Our
approach is to tell you a few basic things about each of the items above—enough
so that you know, as you start making your first pictures, which things you're doing
are approximations and which are correct—and then take you through some very
effective approximate approaches to making pictures. Only then do we return to
the higher-level goal of understanding the ideal and how we might approach it.
Chapter 26 describes the physics of light in considerable detail. Right now, we
rely on your intuitive understanding of light and lay out some basic principles that
we'll refine in later chapters.
• Light propagates along straight-line rays in empty space, stopping when it
meets a surface.
• Light bounces like a billiard ball from any shiny surface that it meets,
following an “angle of incidence equals angle of reflection” model, or
is absorbed by the surface, or some combination of the two (e.g., 40%
absorbed, 60% reflected).
