CODEWITHSUNDEEP
sprite-kitskemitternode
Todd
Todd

Reputation: 153

SKEmitterNode not acting as expected

In my SK game, I have a helicopter that launches rockets. The heli can only have one rocket on the screen at a time, the reason being that I didn't want to have to create a new SKEmitterNode every time a rocket is launched, because it seems this would be taxing on the CPU, having to unarchive the emitter every time.

Therefore, the rocket is a single instance. When someone launches a rocket, it is added to the scene as a child of the scene, launched, and when it hits something, removed from it's parent.

In my update{} metho, here's some psuedo-code:

if ([rocket parent]) {
     rocketSmoke.position = rocket.position;
     rocketSmoke.numParticlesToEmit = 0;
}else{
     rocketSmoke.numParticlesToEmit = 1;
}

So basically, the emitter follows the rocket if it exists and if it doesn't exist, the emitter turns itself off. No, I cannot just add the emitter as a child of the rocket because then when the rocket hits an object and I call removeFromParent the smoke trail behind the rocket will instantly dissapear and that's not the effect I'm going for.

The problem is, when a new rocket is launched and numParticlesToEmit is set back to zero, the particle emitter acts like it's been emitting particles the entire time! I want the particle emitter to simply turn back on, but a bunch of smoke instantaneously appears behind the helicopter as well. You can observe this effect by playing with an emitter file in SK and setting the "max" on the particles to emit to 1, and then setting it back to zero: your screen will instantaneously fill back up as if it had been emitting particles the whole time. Obviously that's not what I want.

I also can't call resetSimulation, because that will remove all existing particles, and so any lingering smoke from the last launch will instantaneously disappear, which would look pretty unnatural if two rockets were launched one after another.

Is my only option to write my own emitter?

Upvotes: 0

Views: 219

Answers (1)

meisenman
meisenman

Reputation: 1828

Create new instances of the emitter for each different rocket. That will resolve your problem.

If it becomes "Too Taxing on the CPU" then create two emitters and alternate which one is used.

Ex. Fire rocket 1, use emitter 1.
Fire rocket 2, use emitter 2.
Fire rocket 3, use emitter 1.

This will give you time for the emitter to finish the effect you want when a rocket hits something while also allowing your next rocket's emitter to behave as desired.

Upvotes: 0

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