Fundamentals of Computer Graphics, 3rd Edition

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Naty Hoffman

Computer Graphics in Games

Of all the applications of computer graphics, computer and video games attract

perhaps the most attention. The graphics methods selected for a given game have

a profound effect, not only on the game engine code, but also on the art asset

creation, and even sometimes on the gameplay, or core game mechanics.

Although game graphics rely on the material in all of the preceding chapters,

two chapters are particularly germane. Games need to make highly efficient use of

graphics hardware, so an understandingof the material in Chapter 18 is important.

Of course, games are interactive applications, and, as such, many of the principles

detailed in Chapter 19 apply.

In this chapter, I will detail the specific considerations that apply to graph-

ics in game development, from the platforms on which games run to the game

production process.

26.1 Platforms

Here, I use the term platform to refer to a specific combination of hardware, op-

erating system, and API (application programming interface) for which a game

is designed. Games run on a large variety of platforms, ranging from virtual

machines used for browser-based games to dedicated game consoles using spe-

cialized hardware and APIs.

In the past, it was common for games to be designed for a single platform.

The increasing cost of game development has made this rare; multiplatform game

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654 26. Computer Graphics in Games

development is now the norm. The incremental increase in development cost to

support multiple platforms is more than repaid by a potential doubling or tripling

of the customer base.

Some platforms are quite loosely defined. For example, when developing a

game for the Windows PC platform, the developer must account for a very large

variety of possible hardware configurations. Games are even expected to run (and

run well) on PC configurations that did not exist when the game was developed!

This is only possible due to the abstractions afforded by the APIs defining the

Windows platform.

One way in which developers account for wide variance in graphics perfor-

mance is by scaling—adjusting graphics quality in response to system capabil-

ities. This can ensure reasonable performance on low-end systems, while still

achieving competitive visuals on high-performance systems. This adjustment is

sometimes done automatically by profiling the system performance, but more of-

ten this control is left in the hands of the user, who can best judge his personal

preferences for quality versus speed. Display resolution is easiest to adjust, fol-

lowed by antialiasing quality. It is also fairly common to offer several quality

levels for visual effects such as shadows and motion blur, including the option of

turning the effect off entirely.

Differences in graphics performance can be so large that some machines may

not run the game at a playable frame rate, even with the lowest quality settings;

for this reason PC game developers publish minimum and recommended machine

specifications for each game.

As platforms, game consoles are strictly defined. When developing a game

for, e.g., Nintendo’s Wii console, the developer knows exactly what hardware the

game will run on. If the platform’s hardware implementation is changed (often

done to reduce manufacturing costs), the console manufacturer must ensure that

the new implementation behaves exactly like the previous one, including timing

and performance. This is not to say that the console developer’s task is easy; con-

sole APIs tend to be much less abstract and closer to the underlying hardware.

This gives console development its own set of difficulties. In some sense, mul-

tiplatform development (which commonly includes at least two different console

platforms and often Windows as well) is the hardest of all, since the multiplatform

game developer has neither the assurance of a fixed platform or the convenience

of a single high-level API.

Browser-based virtual machines such as Adobe Flash are an interesting class

of game platforms. Although such virtual machines run on a wide class of hard-

ware from personal computers to mobile phones, the high degree of abstraction

provided by the virtual machine results in a stable and unified development plat-