I am trying to implement the arrive steering behavior that can be found in the book "Programming Game AI by Example". My project is in C# so I had to rewrite the code that came with the book. Below is the relevant part of my steering behavior class.
public Vector2 SteeringForce { get; private set; }
public Vector2 Target { get; set; }
private enum Deceleration
{
Fast = 1,
Normal = 2,
Slow = 3
}
private Vector2 Arrive(Vector2 target, Deceleration deceleration)
{
Vector2 toTarget = target - Position;
double distance = toTarget.Length();
if (distance > 0)
{
//because Deceleration is enumerated as an int, this value is required
//to provide fine tweaking of the deceleration..
double decelerationTweaker = 0.3;
double speed = distance / ((double)deceleration * decelerationTweaker);
speed = Math.Min(speed, MaxSpeed);
Vector2 desiredVelocity = toTarget * speed / distance;
return desiredVelocity - Velocity;
}
return new Vector2();
}
private Vector2 SumForces()
{
Vector2 force = new Vector2();
if (Activated(BehaviorTypes.Arrive))
{
force += Arrive(Target, Deceleration.Fast);
if (!AccumulateForce(force))
return SteeringForce;
}
return SteeringForce;
}
private bool AccumulateForce(Vector2 forceToAdd)
{
double magnitudeRemaining = MaxForce - SteeringForce.Length();
if (magnitudeRemaining <= 0)
return false;
double magnitudeToAdd = forceToAdd.Length();
if (magnitudeToAdd > magnitudeRemaining)
magnitudeToAdd = magnitudeRemaining;
SteeringForce += Vector2.Normalize(forceToAdd) * magnitudeToAdd;
return true;
}
public Vector2 Calculate()
{
SteeringForce.Zero();
SteeringForce = SumForces();
SteeringForce.Truncate(MaxForce);
return SteeringForce;
}
And this is how one of my game objects uses the steering behavior class:
public override void Update(double deltaTime)
{
Vector2 steeringForce = SteeringBehaviors.Calculate();
Vector2 acceleration = steeringForce / Mass;
Velocity = Velocity + acceleration * deltaTime;
Velocity.Truncate(MaxSpeed);
Position = Position + Velocity * deltaTime;
}
The problem is that I get an oscillating behavior around the target position, the object oscillates less and less and after awhile it stops at the target position. Can anyone see anything in the code I have posted that would cause this oscillating behavior? I fail to see what I have done wrong when I rewrote the code into C# from C++. The samples accompanying the book obviously work so I don't expect any errors in the original code.
I appreciate any help.
