public void Update(GameTime gameTime)
{
if (Paused)
{
return;
}
//Update the total time
totalTimeAlive += (float)gameTime.ElapsedGameTime.TotalMilliseconds;
//Handle being dead
if (totalTimeAlive > EmitterLifespanMs || !Alive)
{
Kill();
return;
}
//Cache the initial value so we can do computations and get the exact position
var currentEmissionArea = EmissionArea;
//And move the emitter to its starting position
var emitterDelta = EmitterVelocity * (float)gameTime.ElapsedGameTime.TotalSeconds;
//Move the emitter based on the velocity
EmissionArea = new RectangleF(EmissionArea.X + emitterDelta.X, EmissionArea.Y + emitterDelta.Y,
EmissionArea.Width, EmissionArea.Height);
//Keep track of how many particles we can create
int numberOfParticlesToCreate = GetNumberOfParticlesToCreate();
if (numberOfParticlesToCreate <= 0)
{
return; //No particles to make, nothing to do
}
//Spawn the particles
for (var i = 0; i < numberOfParticlesToCreate; i++)
{
//Get one of the allowed assets (randomly)
var asset = BasicHelpers.ChooseRandom(Sprites);
var fadeOutTime = GetRandomBetween(MinFadeOutMs, MaxFadeOutMs);
var fadeInTime = GetRandomBetween(MinFadeInMs, MaxFadeInMs);
Vector2 velocity = GetRandomBetween(MinVelocity, MaxVelocity);
Vector2 acceleration = GetRandomBetween(MinAcceleration, MaxAcceleration);
float rotation = GetRandomBetween(MinRotation, MaxRotation);
//Get the size and scale either uniformly or randomly
Vector2 size;
if (ScaleUniform)
{
var factor = GetRandomBetween(0, 1);
var distX = MaxSize.X - MinSize.X;
var distY = MaxSize.Y - MinSize.Y;
size = new Vector2(distX * factor + MinSize.X, distY * factor + MinSize.Y);
}
else
{
size = GetRandomBetween(MinSize, MaxSize);
}
//Do you really have to ask with that variable name?
if (CalculateVelocityAndAccelerationRelativeToRotation)
{
var rotationRel = new Vector2(
(float)Math.Sin(rotation), (float)-Math.Cos(rotation)
);
velocity *= rotationRel;
acceleration *= rotationRel;
}
//And create the actual particle
var particle = new Particle()
{
Acceleration = acceleration,
SpriteInfo = asset,
ColorMask = GetRandomBetween(MinColorMask, MaxColorMask),
FadeInMs = fadeInTime,
FadeOutMs = fadeOutTime,
LifespanMs = GetRandomBetween(MinLifespanMs, MaxLifespanMs) + fadeInTime + fadeOutTime,
Position = GetRandomPosition(currentEmissionArea),
Rotation = rotation,
RotationVelocity = GetRandomBetween(MinRotationVelocity, MaxRotationVelocity),
Size = size,
Velocity = velocity,
RenderBelowObjects = RenderBelowObjects,
GrowInsteadOfFadeIn = ShrinkInsteadOfFadeOut,
ShinkInsteadOfFadeOut = ShrinkInsteadOfFadeOut
};
//Move the emitter to the exact location it should be for this particle
var exactEmitterDelta = EmitterVelocity *
(((float)i / numberOfParticlesToCreate) * (float)gameTime.ElapsedGameTime.TotalSeconds);
//Move the emitter based on the velocity
currentEmissionArea =
new RectangleF(EmissionArea.X + exactEmitterDelta.X, EmissionArea.Y + exactEmitterDelta.Y,
EmissionArea.Width, EmissionArea.Height);
//And add it to the list
Container.AddParticle(particle);
totalParticlesCreated++; //Note that we created another particle
}
}