Game Development Reference
Guns and Explosions
One of the most widely successful video game genres is the venerable first-person
shooter. Ever since the breakthrough games of Wolfenstein 3D and Doom , the first-
person shooter has received the lion's share of research and development budgets. It is
amazing that the physics of aiming a gun and of a bullet traveling through the air are
rarely modeled accurately. In general, game designers treat guns like laser beams so that
wherever you point them, the bullet goes in an infinitely straight line. In this chapter
we'll discuss how to more accurately model both aiming and the trajectory of bullets,
which is known as ballistics.
There are actually four subtopics of ballistics. Internal ballistics is the study of what
happens to the bullet inside the barrel of the gun; transitional ballistics is the study of
what happens as the bullet exits the barrel. Once the bullet has fully exited the barrel, it
is in the realm of external ballistics . At this point the only acceleration is that of gravity,
and the same forces discussed in Chapter 6 take over. The last topic is terminal ballis‐
tics , which is the study of what happens when the bullet hits its target. The last two topics
are the ones we'll discuss here. The other phases are more important to firearm man‐
ufacturers and not so much to the shooter. If you don't recall the material in Chap‐
ter 6 , we highly recommend that you review it before continuing.
While we aren't very concerned about what happens in the barrel of the gun, there are
a few tidbits we do need to know about the system. The first is where the barrel is pointed.
This is referred to as the gun's aim , and is almost universally controlled by where the
mouse is on the screen.