// 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 = ParticleSystem.RandomBetween(0, MathHelper.TwoPi);
}
// this function is called when we want to demo the explosion effect. it
// updates the timeTillExplosion timer, and starts another explosion effect
// when the timer reaches zero.
private void UpdateExplosions(float dt, Viewport viewport)
{
timeTillExplosion -= dt;
if (timeTillExplosion < 0)
{
Vector2 where = Vector2.Zero;
// create the explosion at some random point on the screen.
where.X = ParticleSystem.RandomBetween(0, viewport.Width);
where.Y = ParticleSystem.RandomBetween(0, viewport.Height);
// the overall explosion effect is actually comprised of two particle
// systems: the fiery bit, and the smoke behind it. add particles to
// both of those systems.
explosion.AddParticles(where);
smoke.AddParticles(where);
// reset the timer.
timeTillExplosion = TimeBetweenExplosions;
}
}
