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Hi!
I'm trying to achieve a trail effect on my particle system each time a particle gets drawn. I'm using particle designer for the emitter. I've searched the forums but I couldn't find anything. Could someone tell me if there's a simple way to do this? If there isn't, could someone guide me on what needs to be done?
Thanks!
There is no simple way to get this done ASAIK. A couple of potential approaches:
1) each "particle" is actually an "emitter" that generates its particles on the same spot (no gravity, no speed) and you create / move / destroy-reuse these emitters around with your own custom logic. As the emitters move, they leave a trail behind.
2) create a custom class that remembers the position of all particles in an emitter and draws them without animating them. It's essentially a CCSpriteSheet whose sprites are hooked into specific particles in a given particle emitter. You update the sprite sheet sprites with current particle positions before the particle positions are updated, effectively remembering their previous positions. You then draw this sprite sheet with 50% opacity over the real particles generated by the emitter to simulate motion blur.
There used to be a motion streak effect in the experimental folder....
CCMotionStreak, it's part of the library now; see here:
http://www.cocos2d-iphone.org/api-ref/latest-stable/interface_c_c_motion_streak.html
Since individual particles are not nodes, you may have to do some finagling to get it to work....
I saw the MotionStreak example but had no idea how to add it to each particle. I guess I'll try to create several emitters as if they were particles and control their behavior. I don't know which would be better (in performance), motionsteak to each particle or emitter for each particle?
Hmmm interesting question, I suppose the particle emitter is probably doing more work because it takes several factors like gravity and radial accel into account...
It sounds like it'd be a cool effect if you get it to work though.
I've managed to obtain the effect, but performance sucks! =(
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What I did was create a custom class for the emitter:
This is my class:
TrailParticles.h
#import "cocos2d.h"
@interface TrailParticlesSystem : CCNode
{
int totalParticles;
float life;
float lifeVar;
float timeToLive;
}
@property (nonatomic,readwrite,assign) float life;
@property (nonatomic,readwrite,assign) float lifeVar;
-(id) initWithTotalParticles:(int) numberOfParticles;
@endTrailParticlesSystem.m
#define kParticlesStartingTag
#import "TrailParticlesSystem.h"
#import "EmittingParticle.h"
static ccColor4F fireworksColors[] = {
{1.0f, 0.0f, 0.0f, 1.0f}, //Red
{0.0f, 1.0f, 0.0f, 1.0f}, //Green
{0.0f, 0.0f, 1.0f, 1.0f}, //Blue
{1.0f, 1.0f, 0.0f, 1.0f}, //Yellow
{1.0f, 1.0f, 1.0f, 1.0f}, //White
{1.0f, 0.0f, 1.0f, 1.0f}, //Purple
{1.0f, 0.5f, 0.0f, 1.0f} //Orange
};
@implementation TrailParticlesSystem
@synthesize life, lifeVar;
- (id) initWithTotalParticles:(int) numberOfParticles
{
self.life = 1.0f;
self.lifeVar = 0.5;
ccColor4F startColor = fireworksColors[arc4random()%7];
ccColor4F endColor = fireworksColors[arc4random()%7];
if( (self=[super init]) )
{
timeToLive = life + lifeVar;
totalParticles = numberOfParticles;
for (int i =0; i< totalParticles; i++)
{
EmittingParticle *particle = [EmittingParticle node];
particle.startColor = startColor;
particle.endColor = endColor;
particle.life = self.life;
particle.lifeVar = self.lifeVar;
particle.velocity = ccp(CCRANDOM_MINUS1_1()*50,CCRANDOM_MINUS1_1()*50);
particle.acceleration = ccp (0.0, -40.0);
[particle setPosition:self.position];
[self addChild:particle z:0 tag:kParticlesStartingTag + i];
}
[self scheduleUpdate];
}
return self;
}
- (void)update:(ccTime)dt
{
EmittingParticle *particle;
CCARRAY_FOREACH([self children], particle)
[particle updateSystem:dt];
timeToLive -= dt;
if (timeToLive <= 0.0)
[self removeFromParentAndCleanup:YES];
}
- (void)dealloc
{
[super dealloc];
}
@endI then add it to my scene like this:
TrailParticlesSystem *emitter = [[TrailParticlesSystem alloc] initWithTotalParticles:40];
emitter.position = pos;
[self addChild:emitter];Is there a way to preallocate all the emitters in the particle system or copy them without allocing?
You can re-purpose an emitter using reset() (or some method like it - I don't have the code in front of me). That way you could have a cache of emitters and just re-use them as you go along. I've done that in a number of projects and it works well.
Another option would be to derive from ParticleSystem (or copy the code and tweak it to your liking) such that the draw() method would draw several images per particle, interpolated with position and size from previous frame to the current frame.
The problem with your current solution is that you keep creating new systems AND that each system is its own OpenGL draw call (those are expensive). If you can mush it all into one draw call, your performance should increase considerably.
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