// initialize is called by ParticleSystem to set up the particle, and prepares
// the particle for use.
public void Initialize(Vector2 position, Vector2 velocity, Vector2 acceleration,
float lifetime, float scale, float rotationSpeed)
{
// set the values to the requested values
this.Position = position;
this.Velocity = velocity;
this.Acceleration = acceleration;
this.Lifetime = lifetime;
this.Scale = scale;
this.RotationSpeed = rotationSpeed;
// reset TimeSinceStart - we have to do this because particles will be
// reused.
this.TimeSinceStart = 0.0f;
// set rotation to some random value between 0 and 360 degrees.
this.Rotation = LaserBikes.RandomBetween(0, MathHelper.TwoPi);
}
/// <summary>
/// InitializeParticle randomizes some properties for a particle, then
/// calls initialize on it. It can be overriden by subclasses if they
/// want to modify the way particles are created. For example,
/// SmokePlumeParticleSystem overrides this function make all particles
/// accelerate to the right, simulating wind.
/// </summary>
/// <param name="p">the particle to initialize</param>
/// <param name="where">the position on the screen that the particle should be
/// </param>
protected virtual void InitializeParticle(Particle p, Vector2 where)
{
// first, call PickRandomDirection to figure out which way the particle
// will be moving. velocity and acceleration's values will come from this.
Vector2 direction = PickRandomDirection();
// pick some random values for our particle
float velocity =
LaserBikes.RandomBetween(minInitialSpeed, maxInitialSpeed);
float acceleration =
LaserBikes.RandomBetween(minAcceleration, maxAcceleration);
float lifetime =
LaserBikes.RandomBetween(minLifetime, maxLifetime);
float scale =
LaserBikes.RandomBetween(minScale, maxScale);
float rotationSpeed =
LaserBikes.RandomBetween(minRotationSpeed, maxRotationSpeed);
// then initialize it with those random values. initialize will save those,
// and make sure it is marked as active.
p.Initialize(
where, velocity * direction, acceleration * direction,
lifetime, scale, rotationSpeed);
}
/// <summary>
/// PickRandomDirection is used by InitializeParticles to decide which direction
/// particles will move. The default implementation is a random vector in a
/// circular pattern.
/// </summary>
protected virtual Vector2 PickRandomDirection()
{
float angle = LaserBikes.RandomBetween(0, MathHelper.TwoPi);
return(new Vector2((float)Math.Cos(angle), (float)Math.Sin(angle)));
}
/// <summary>
/// Constructs a new ParticleSystem.
/// </summary>
/// <param name="game">The host for this particle system. The game keeps the
/// content manager and sprite batch for us.</param>
/// <param name="howManyEffects">the maximum number of particle effects that
/// are expected on screen at once.</param>
/// <remarks>it is tempting to set the value of howManyEffects very high.
/// However, this value should be set to the minimum possible, because
/// it has a large impact on the amount of memory required, and slows down the
/// Update and Draw functions.</remarks>
protected ParticleSystem(LaserBikes game, int howManyEffects)
: base(game)
{
this.game = game;
this.howManyEffects = howManyEffects;
}
public ExplosionParticleSystem(LaserBikes game, int howManyEffects)
: base(game, howManyEffects)
{
}
static void Main()
{
using (var game = new LaserBikes())
game.Run();
}
