// 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 = RandomHelper.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 = (this._useDirection) ? this._direction : this.PickRandomDirection();
// pick some random values for our particle
float velocity =
RandomHelper.RandomBetween(this.minInitialSpeed, this.MaxInitialSpeed);
float acceleration =
RandomHelper.RandomBetween(this.minAcceleration, this.maxAcceleration);
float lifetime =
RandomHelper.RandomBetween(this.minLifetime, this.maxLifetime);
float scale =
RandomHelper.RandomBetween(this.minScale, this.maxScale);
float rotationSpeed =
RandomHelper.RandomBetween(this.minRotationSpeed, this.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 = RandomHelper.RandomBetween(0, MathHelper.TwoPi);
return(new Vector2((float)Math.Cos(angle), (float)Math.Sin(angle)));
}