private void FireParticles(GameTime gameTime, ParticleManager <ParticleState> particleManager)
{
double t = gameTime.TotalGameTime.TotalSeconds;
var direction = new Vector2((float)Math.Sin(Ship.Rotation), (float)Math.Cos(Ship.Rotation) * -1);
float aimAngle = direction.ToAngle();
Quaternion rot = Quaternion.CreateFromYawPitchRoll(0, 0, aimAngle);
// The primary velocity of the particles is 3 pixels/frame in the direction opposite to which the ship is travelling.
Vector2 baseVel = direction.ScaleTo(2);
// Calculate the sideways velocity for the two side streams. The direction is perpendicular to the ship's velocity and the
// magnitude varies sinusoidally.
var perpVel = new Vector2(baseVel.Y, -baseVel.X) * (0.6f * (float)Math.Sin(t * 10));
var sideColor = new Color(200, 38, 9); // deep red
var midColor = new Color(255, 187, 30); // orange-yellow
var pos = Ship.Position; // position of the ship's exhaust pipe.
const float alpha = 0.7f;
// middle particle stream
Vector2 velMid = baseVel + random.NextVector2(0, 1);
particleManager.CreateLineParticle(pos, Color.White * alpha, 60f, new Vector2(0.5f, 1),
new ParticleState(velMid, ParticleType.Enemy));
particleManager.CreateGlowParticle(pos, midColor * alpha, 60f, new Vector2(0.5f, 1),
new ParticleState(velMid, ParticleType.Enemy));
// side particle streams
Vector2 vel1 = baseVel + perpVel + random.NextVector2(0, 0.3f);
Vector2 vel2 = baseVel - perpVel + random.NextVector2(0, 0.3f);
particleManager.CreateLineParticle(pos, Color.White * alpha, 60f, new Vector2(0.5f, 1),
new ParticleState(vel1, ParticleType.Enemy));
particleManager.CreateLineParticle(pos, Color.White * alpha, 60f, new Vector2(0.5f, 1),
new ParticleState(vel2, ParticleType.Enemy));
particleManager.CreateGlowParticle(
pos, sideColor * alpha, 60f, new Vector2(0.5f, 1),
new ParticleState(vel1, ParticleType.Enemy)
);
particleManager.CreateGlowParticle(
pos, sideColor * alpha, 60f, new Vector2(0.5f, 1),
new ParticleState(vel2, ParticleType.Enemy)
);
}