Optimize ParticleSystems « cocos2d for iPhone

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Optimize ParticleSystems

(66 posts) (22 voices)

Started 2 years ago by adpro
Latest reply from neigaard

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adpro
Member

Hello,

As some of you know, I was asking questions about some other stuff earlier and it led me to the suggestion of pre-allocating particles for my ParticleExplosion I am using for my game.

Basically, I am using a bunch of particle explosions when sprites interact. Think of space invaders, but with different types of bullets that interact differently with different enemies. A lot of the time, there will be explosions when two sprites interact. Many explosions can be going on at the same time - in fact, there are usually at least 2 explosions going on at the exact same time.

I figured I would start a thread to help me, and others in search of the same answers, find answers to optimizing particle systems for their games.

After a bunch of explosions happen in my game (there has to be a lot), it slows down to about 30-40fps. It doesn't start slowing down until after about 150-200+ explosions.

It was suggested to pre-allocate the particles. I have gone into particle.m and other files, but haven't been able to figure out how to do this exactly. I'm also new to chipmunk, cocos2d, cocoa and objective-c, so maybe I am missing something simple. I searched google to see if there was anything, but I couldn't find anything.

I'm thinking these answers would help a lot of people, so any information would be greatly appreciated. I'll post what I find as well in here.

Thanks all!

Posted 2 years ago #
jd
Member

I'm wondering if it might be more efficient (and easier to implement) to have sprite explosion animations and just run those on impact.

Posted 2 years ago #
edisonslabs
Member

When I previously mentioned preallocating particles, it's something like this:

1. In your interface, make a NSMutableArray
2. In your layer/scene init function, alloc and init 10-20 or so ParticleSystems of your choice and add them into the array. Then call the method "stop system" (or something similar) on them, and then add them to your layer.
3. When you need to show particles, get one of the particle systems in the array and call reset system on it. How to choose which particle system in an array? I did it sequentially.

Posted 2 years ago #
zombie
Member

It will be MUCH faster when you only use one particle system. Make a spawn method that will add an explosion to that system. Call this method multiple times to spawn more than one explosion. Takes some changes/additions in/to cocos, but its not hard. And the speed improvement will be huge, if you have many particle systems.

Just compare

1 explosion with nX particles
to
n explosions with X particles

and you will see if this the way you should go.

Thomas

Posted 2 years ago #
coolman
Member

I use the method that edisonlabs told. And works fine.

zombie, can you put a brief sample code from your idea?

Posted 2 years ago #
riq
Key Master

yes, the next step is to have a sort of ParticleSystemManager, so particle systems of the same type are drawn all together.

Posted 2 years ago #
zombie
Member
here you go.
```
// do not mix spawn with addParticle (so also not with self emitting systems)
- (void) spawnParticles:(uint)n
{
	Particle* particle;
	for(uint i=0; i<n; i++)
	{
		particle = &particles[ particlePos ];
		[self initParticle: particle];
		particlePos++;
		particleCount++;
		if(particlePos==totalParticles)
		{
			particlePos=0;
		}
		if(particleCount>totalParticles)
		{
			particleCount=totalParticles;
		}
	}
}
```
This adds n particles. If there are already too much particles spawned, the oldest particles are reused. And this only works when you do not have systems that spawn particles continously. If you need that you have to schedule a timer method that calls spawnParticles every frame.

I also implemented a kind of a manager for my particle systems (batching calls of similiar systems), but there is too much code inside which is specific too my game as I also changed other thing of the particle systems. Would not be very useful.

Hope that helps.

Thomas
Posted 2 years ago #
zombie
Member

is there a way to edit posts? The code doesnt look nice. Sorry for that.

Posted 2 years ago #
riq
Key Master

done. edited.

Posted 2 years ago #
coolman
Member

Thanks zombie, interesting code.

Posted 2 years ago #
LongJohnnyE
Member

I did this for StickWars. I created an object to hold an NSArray of 10 pre-alloced 'explosion' objects and serve available explosion objects that were inactive.

I was very happy when the older bug with reset on a particle system was fixed :). That bug was driving me crazy before I figured out what was going wrong.

Unfortunately, I'm still kinda a newbie and wasn't really able to determine if caching the particle systems helped performance a lot, but my 'eyeball' tests by watching FPS seemed to say yes.

Posted 2 years ago #
zombie
Member

Using only one ParticleSystem has two advantages:

1) It is faster, as GL calls are batched.
2) You are not fixed in the number of e.g. explosions you can spawn simultaneously, just in the number of total particles.

Thomas

Posted 2 years ago #
coolman
Member

zombie,

But you can make only one explision .. right?

Posted 2 years ago #
zombie
Member

no, as much as you need.

-Set the position of the particleSystem for explosion 1
-call spawn

-Set the position of the particleSystem for explosion 2
-call spawn

The position is stored in each particle, so it is save to change it after calling spawn. You must use world coordinates for the system of course.

To make the spawn method work you have to make some changes in the PointParticleSystem.m, too. (Do not remove the dead particles,...)

Thomas

Posted 2 years ago #
coolman
Member

Interesting,

Can you submit a path to cocos2d with this feature?

It would be great to have it

Posted 2 years ago #
edisonslabs
Member

Hm.. Thanks for your suggestion, zombie. I'm trying to think of other easier ways to optimize my particle system, but the only way left I can think of is batching opengl calls via your method.

BTW, is there an easy way to experiment with particle system values (like during run time)? Or do I need to create my own particle system experimenter app? :/

Posted 2 years ago #
zombie
Member

My method is not really hard to implement, unfortunately I have no time currently to isolate the code and submit a patch. There are other changes to the particle system, too. If someone has specific questions however, I am happy to help if I can.

BTW:
I would buy a cocos particle system builder app :)

Posted 2 years ago #
zombie
Member

a note on how we handle code changes to cocos, as the main reason for not changing the ParticleSystem is that you have to do it in cocos directly:

We are working with the Cocos Trunk. All cvs folders are backed up. We have a script that chnages our cvs folders wiht the one from cocos and then updates from the cocos repository. After that it copies back our cvs folders. Doing it like this merges our changes with future cocos changes.

Maybe this is helpful for someone...

Posted 2 years ago #
Codemattic
Moderator

Has anyone been able to measure the performance gains you get from pre allocating particles?

Posted 2 years ago #
SpaceHunter
Member

"To make the spawn method work you have to make some changes in the PointParticleSystem.m, too. (Do not remove the dead particles,...)"

Zombie, could you outline (if you have time) the changes you are referring too?

Posted 2 years ago #
coolman
Member

Agreed with SpaceHunter, this could be quite interesting.

Posted 2 years ago #
edisonslabs
Member

"Has anyone been able to measure the performance gains you get from pre allocating particles?"

All I have observed was, if I was to allocate particles on the fly, my FPS would drop to 40 or lower when there were multiple particle explosions happening on screen.

If I was to pre-allocate particles, my FPS would stay 60, until there are too many things going on.

I know these data may not mean much, but there is definitely a noticeable boost in the FPS when you preallocate the particles.

Posted 2 years ago #
Codemattic
Moderator

thanks edisonlabs! Even if its not scientific, going from around 40 back to 60 sounds pretty good.

Posted 2 years ago #
coolman
Member

Yes Codemattic,

Is worth the try having the ParticleSystems initiated and stopped, and just resetsystem when you need one.

Posted 2 years ago #
zombie
Member
Here is what I changed in the step function of the pointparticlesystem. I removed the following code:
```
// removed by me
			//		} else {
			//			// life < 0
			//			if( particleIdx != particleCount-1 )
			//				particles[particleIdx] = particles[particleCount-1];
			//			particleCount--;
```
You also have to set the emissionRate of a system that uses the spawn mathod to 0. When I need a system that emits particles over time, I do that with a scheduled timer for the object that emits the particles.

So you have one particleSystem and several objects that spwn particles with that system. Each object sets the source of the particleSystem to the requeried position and calls the spawn method. Hope this is clear, and I hope that this was all I changed to make this work, as I changed several things for other extensions to the particle systems, too.

Zombie
They are coming... - Follow me on Twitter: http://twitter.com/ZombieSmash
Posted 2 years ago #
coolman
Member

Will dig into that, thanks!

Posted 2 years ago #
edisonslabs
Member

Thanks zombie! Will take a look into that.

Posted 2 years ago #
conor
Member

when you mention "spawn" method what are you referring to?

nevermind found this http://www.cocos2d-iphone.org/forum/topic/88#post-523 explaining the method.

Posted 2 years ago #
conor
Member

would this work if i have a number of objects all emitting fire at the same time? I tried setting this up as described but it seems when one objects starts emitting the rest stop. also if i comment out the pointparticle.m as zombie describes the simulator freezes, no error in console or debugger.

Posted 2 years ago #
vutronic
Member

Conor, in my method which you referenced to, you can only launch one explosion at a time. I believe making the changes zombie described above allow you to run multiple explosions at different positions using just one particle system. I haven't looked into it yet.

Posted 2 years ago #

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