Game Development Reference
In-Depth Information
CHAPTER 12
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The Physics of Solids
F or the most part in this topic, we have been studying the external physics of various objects—
how they fly through the air, drive across land, float over water. The main emphasis in the
earlier chapters has been in modeling the external forces of thrust, drag, lift, gravity, and fric-
tion. In this chapter, we will explore some internal physics of objects you may use in your game
simulations. For example, rather than discuss what happens to a projectile that is flying towards
a target, we will look at what happens to the target once the projectile strikes it.
Many topics could be characterized under the title “physics of solids.” In this chapter,
we will explore two subjects that have application to game programming scenarios. The first
subject we will cover is ballistic impacts—what happens to a target when a projectile or other
object slams into it. The second topic we will discuss is how heat energy is conducted through
solid objects. The applications to game programming for heat conduction might include deter-
mining how long before a gas tank exposed to a flame would explode or calculating how long it
would take a laser to burn through the hull of a spaceship.
Specific points that will be covered in this chapter include the following:
What happens to a projectile and target during a ballistic impact
The concepts of energy and work and how they relate to a ballistic impact
Ways to model the penetration of steel armor
Modeling arrow penetrations
Momentum and blunt trauma due to ballistic impact
The physics of body wounds
How Fourier's law relates heat energy transfer to a temperature gradient
The heat conduction equation
Methods to solve the heat conduction equation using the error function
Ballistic Impacts
A ballistic impact occurs when a projectile strikes another object at high speed. When this
happens, basically three things can happen: the projectile can bounce off of the object, it can
partially penetrate the object, or it can pass completely through the object. Which of these
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