Game Development Reference
In-Depth Information
Cars
You can create a lot of exciting game simulations involving cars, whether it's car races, car
chases, or just simulating the life of a taxi driver. Putting realistic physics into a car simulation
really just involves applying some basic concepts from Newtonian mechanics and kinematics
with a little knowledge about how power is transferred from the engine to the wheels.
In this section, we'll start with the basics of straight-line driving and explore topics such as
the forces that act upon a moving car, engine torque, and how gears and a transmission transfers
the engine power to the wheels. We'll revisit the subjects of aerodynamics and rolling friction
as they apply to the motion of a car. With these topics in hand, we'll explore how to model the
acceleration and velocity of a car. Later, we'll investigate such topics as what happens when a
car drives around a curve and wheel traction, and we'll also develop a simple car simulator.
Keep in mind when reading this section that it provides the basic theory of car physics.
It will give you the information you need to create a fairly realistic car simulation. Advanced
topics such as weight transfer during braking and cornering are not included in the model we
will develop, but if you want to get “fancy” with your car simulation, it would be pretty straight-
forward to add advanced effects to the basic model. We'll discuss briefly how to go about adding
advanced effects at the end of the chapter.
A Brief History of the Automobile
People have been thinking about, designing, and building motorized vehicles for a very long
time. The first working motorized vehicle was a steam-powered tractor built by a French
engineer named Nicolas Cugnot in 1769. It was intended to pull cannons and had a top speed
of 4
km/hr
. Mr. Cugnot was also the first person to have a car accident when he drove his vehicle
into a stone wall in 1771.
The development of automobiles took a big leap forward towards the end of the nineteenth
century when a German engineer named Karl Benz designed and built the first vehicle powered by
an internal combustion gasoline-powered engine. While cars gained in popularity over the
next 20 years, they were quite expensive and considered mostly toys for the rich. In 1913, the
American Henry Ford perfected the assembly line, which could assemble a Model T car in only
93 minutes. Such improved productivity greatly reduced the cost of buying a car. By 1927, over
15 million Model T's had been built and sold.
Obviously, cars have never looked back, and they are a crucial element of the transporta-
tion systems of almost every country on Earth. Cars have also become a form of entertainment
for people who like to drive fast, look good, or just generally have a good time.
Basic Force Diagram
A schematic of the forces acting on a car driving in a straight line on an inclined surface is shown
in Figure 8-1. The angle of the slope is equal to
q
. The car is influenced by the forces of gravity,
static friction, rolling friction, and aerodynamic drag—all subjects you have learned about
earlier in the topic. The engine applies a torque,
T
e
, to the car wheels that generates the force
that moves the car forward. In Figure 8-1, the torque is applied to the front wheels of the car.
