Building Player Movement Controllers - C# Game Programming - page 111

toppling over in games, but it comes at a cost. If the car were to roll and flip over, it will roll
in an unrealistic way because of the way that the center of mass will affect its movement.
Look to the stabilizer bar simulation for a more realistic solution, but for now, this is as
far as we go:
// with this simple vehicle code, we set the center of mass
// low to try to keep the car from toppling over
myBody.centerOfMass= new Vector3(0,-4f,0);
If no engine sound source has been set up via the Inspector window of the Unity
editor, the script tries to find it with a call to GameObject.GetComponent(). The sound
source will be stored in engineSoundSource and used solely for engine sound effects:
// see if we can find an engine sound source, if we need to
if( engineSoundSource==null )
{
engineSoundSource= myGO.GetComponent<AudioSource>();
}
}
As with all of the movement controllers, SetUserInput sets a flag to decide whether or
not inputs should be used to drive the vehicle:
public void SetUserInput( bool setInput )
{
canControl= setInput;
}
Unlike other movement controllers from this topic so far, this one introduces a lock
state. The lock state is for holding the vehicle in place without affecting its y -axis. This dif-
fers from just disabling user input as it adds physical constraints to the physics object to
hold it still (its purpose being to hold the vehicle during the counting in at the start of a
race or other similar scenario):
public void SetLock(bool lockState)
{
isLocked = lockState;
}
LateUpdate() starts by checking for input via the GetInput() function, when canCon-
trol is set to true. Next, UpdateEngineAudio() is called to update the pitch of the engine
sound based on the engine speed:
public virtual void LateUpdate()
{
// we check for input in LateUpdate because Unity recommends
// this
if(canControl)
GetInput();
// update the audio
UpdateEngineAudio();
}