Ultimate Game Design : Building game worlds

Building Game Worlds
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U L T I M A T E G A M E D E S I G N
FIGURE 6-2
Simple sine wave attack
Figure 6-2 shows the shape of the resulting attack pattern for enemyactor as a
standard sine wave.
All right, so enemyactor follows the sine wave path. Well that’s okay for one attack
pattern (I think we’ve seen it before), but we want to build many others. In a very simple
shooter, we would probably want at least one unique attack pattern for each game
level. Maybe we want a big lazy sloping attack pattern. We can start to build one by
tweaking the sine wave values.
Here’s a practical point: Plenty of scripting work involves just tweaking or editing
variables, saving, and rebuilding. Sometimes you will spend days just working on
many tweaked script versions for a range of behaviors. In some cases, you won’t even
be writing the scripts or “line commands” as we’re looking at them here; you may
just tweak values to get an intended effect.
Now, let’s change the amplitude of the sine wave to create a different attack pattern.
This example should help demonstrate the idea that shaping many behaviors, like
this simple attack behavior, is often a matter of starting to tweak values:
// Alter sine wave attack for enemyactor by modulating amplitude
function moveEnemy() {
enemyactor.moveLeft();
// Modulate sine wave amplitude by another sine wave
var x = enemyactor.getX()%360;
enemyactor.setY((50*sin(x)+50) * sin(x*4) + 240);
}
Figure 6-3 shows the result of adjusting the attack pattern by modulating amplitude.
Now our enemyactor has a tweaked attack pattern. As you can see, we could make
many other attack patterns by simply changing values and playing around with
numbers. We might create even more types of attack patterns by altering the frequency
of the sine wave.