Cars and Motorcycles - Physics for Game Programmers - page 227

velocity, or braking. The omegaE field is the engine turnover rate in rpm . The names of the other
Car class fields are self-explanatory.
The Car constructor is used to initialize the fields in the Car , DragProjectile , SimpleProjectile ,
and ODE classes. The first thing the constructor does is to call the DragProjectile class constructor.
// The Car constructor calls DragProjectile constructor and
// then initializes the car-specific variables.
public Car(double x, double y, double z,
double vx, double vy, double vz,
double time, double mass, double area,
double density, double Cd, double redline,
double finalDriveRatio, double wheelRadius,
int numberOfGears) {
super(x, y, z, vx, vy, vz, time, mass, area,
density, Cd);
The Car constructor then initializes the fields declared in the Car class with values passed to
the constructor. The size of the gearRatio array is set according to the value of the numberOfGears
field. The gear ratios are initially given dummy values of 1.
// Initialize some fields based on values passed
// to the constructor.
this.redline = redline; // Redline rpm
this.finalDriveRatio = finalDriveRatio; // Final drive ratio
this.wheelRadius = wheelRadius; // Wheel radius
this.numberOfGears = numberOfGears; // Number of gears
// Initialize the array that stores the gear ratios.
// The array is shifted so the first index in the
// array correpsonds to first gear and so on.
// Give all gear ratios the dummy value of 1.0
gearRatio = new double[numberOfGears + 1];
gearRatio[0] = 0.0;
for(int i=1; i<numberOfGears+1; ++i) {
gearRatio[i] = 1.0;
}
Some of the Car field values will be set to the same value for all car classes including the
fields that represent the coefficient of rolling friction, initial engine rpm , starting gear number,
and mode.
// Set some fields the same for all cars.
muR = 0.015; // Coefficient of rolling friction
omegaE = 1000.0; // Engine rpm
gearNumber = 1; // Gear the car is in
mode = "accelerating"; // Accelerating, cruising, or
// braking
}