public void LoadNpcCars(World world, IList<Car> list, int quantity, Texture2D[] textures)
{
list.Clear(); //Delete any existing cars in operation
var rand = new Random();
var laneNum = 0;
for(var i = 0; i < quantity; i++)
{
var spawnAttempts = 0;
var textureId = rand.Next(0, textures.Count()-1);
var newCar = new Car(textures[textureId]);
world.InitializeNpcCar(newCar, laneNum, ref rand);
world.OptimizeSpawnPosition(this, list, newCar, laneNum, ref rand, ref spawnAttempts);
//If the car did not hit its number of maximum spawn attempts, assume it safe-spawned and spawn it
if(spawnAttempts <= World.MaxSpawnAttempts)
{
list.Add(newCar);
laneNum++;
if (laneNum >= world.Lanes.Count())
laneNum = 0;
}
}
}
/// <summary>
/// Checks a given area against all NPCs in order to find a collision - event terminates on the first collision in case there's more than one.
/// </summary>
/// <param name="cars"></param>
/// <param name="toCheck">the area to check for a collision</param>
/// <param name="collided">a reference to the car that collided with the given rectangle</param>
/// <returns>true or false</returns>
public bool CheckNpcHardCollision(IList<Car> cars, Rectangle toCheck, out Car collided)
{
foreach (var car in cars.Where(car => car.HardCollisionBoundary.Intersects(toCheck) && car.IsColliding == false))
{
collided = car;
return true;
}
collided = null;
return false;
}
public void InitializePcCar(Car car)
{
var laneNum = Lanes.Count() / 2;
car.Center = new Vector2((Lanes[laneNum].LaneBox.X + (Lanes[laneNum].LaneBox.Width - car.Width) / 2f), Bounds.Height - car.Height);
car.Velocity = new Vector2(0f, -10f);
}
/// <summary>
/// Recursively looks for an optimal place to spawn an NPC car where it won't collide with any other NPCs
/// </summary>
/// <param name="pcCar"></param>
/// <param name="list"></param>
/// <param name="car">The car we intend to spawn</param>
/// <param name="laneNum">the lane on the freeway the car belongs to</param>
/// <param name="rand">a random number generator we pass by reference</param>
/// <param name="attemptCount">the number of attempts it has taken us to spawn this car</param>
public void OptimizeSpawnPosition(PcCar pcCar, IList<Car> list, Car car, int laneNum, ref Random rand, ref int attemptCount)
{
Car collisionCar;
if ((CheckNpcHardCollision(list, car.SoftCollisionBoundary, out collisionCar)
|| pcCar.SoftCollisionBoundary.Intersects(car.HardCollisionBoundary)
) && attemptCount <= MaxSpawnAttempts)
{
/* All of this code needs to execute whenever an NPC car has:
* 1. Spawned on top of another NPC
* 2. Spawned on top of the PC
* 3. And the maxmimum number of spawn attempts has not been reached.
*/
attemptCount++;
InitializeNpcCar(car, laneNum, ref rand);
OptimizeSpawnPosition(pcCar, list, car, laneNum, ref rand, ref attemptCount);
}
}
public void InitializeNpcCar(Car car, int laneNum, ref Random rand)
{
var yPos = rand.Next(0, Bounds.Height - car.Height);
var velocity = (rand.Next(-45, 45) + 0.5f);
car.Center = new Vector2((Lanes[laneNum].LaneBox.X + (Lanes[laneNum].LaneBox.Width - car.Width) / 2f), yPos);
car.Velocity = new Vector2(0f, velocity);
}