Cloudsdale's fireworks background view.

FireworksView.mm

//
//  FireworksView.m
//  Cloudsdale
//
//  Created by Tyrone Trevorrow on 24/05/12.
//  Copyright (c) 2012 Cloudsdale. All rights reserved.
//

#import <QuartzCore/QuartzCore.h>
#import "FireworksView.h"

@interface FireworksView ()
@property (nonatomic, strong) CALayer *rootLayer;
@property (nonatomic, strong) CAEmitterLayer *mortor;
@property (nonatomic, strong) NSTimer *fireworkTimer;
- (void) setup;
@end

@implementation FireworksView
@synthesize rootLayer, mortor, fireworkTimer;

- (id) init
{
    self = [super init];
    if (self) {
        [self startAfterDelay: 1.0];
    }
    return self;
}

- (id) initWithFrame:(CGRect)frame
{
    self = [super initWithFrame: frame];
    if (self) {
        [self startAfterDelay: 1.0];
    }
    return self;
}

-(void)awakeFromNib 
{
    [self startAfterDelay: 1.0];
}

- (void) startAfterDelay: (NSTimeInterval) delay
{
    [NSObject cancelPreviousPerformRequestsWithTarget: self selector: @selector(setup) object: nil];
    [self performSelector: @selector(setup) withObject: nil afterDelay: delay];
}

- (void) fireworkTimerAction
{
    self.mortor.birthRate = 1;
    double delayInSeconds = 0.00001;
    dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
    dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
        self.mortor.birthRate = 0;
    });
}

- (void) setup
{
    //Create the root layer
	self.rootLayer = [CALayer layer];

	//Set the root layer's attributes
	self.rootLayer.frame = CGRectMake(0, 0, self.bounds.size.width, self.bounds.size.height);
	self.rootLayer.backgroundColor = [UIColor colorWithWhite: 0.0 alpha: 0.0].CGColor;;

	//Load the spark image for the particle
	id img = (id) [UIImage imageNamed: @"Sparkle.png"].CGImage;

	self.mortor = [CAEmitterLayer layer];
	self.mortor.emitterPosition = CGPointMake(self.rootLayer.bounds.size.width / 2.0, self.rootLayer.bounds.size.height);
	self.mortor.renderMode = kCAEmitterLayerAdditive;
    self.mortor.speed = 1.0;
    //self.mortor.birthRate = 0;

	//Invisible particle representing the rocket before the explosion
	CAEmitterCell *rocket = [CAEmitterCell emitterCell];
	rocket.emissionLongitude = (3 * M_PI) / 2;
	rocket.emissionLatitude = 0;
	rocket.lifetime = 1.2;
	rocket.birthRate = 1;
	rocket.velocity = 400;
	rocket.velocityRange = 200;
	rocket.yAcceleration = 250;
	rocket.emissionRange = M_PI / 4;
	rocket.color = [UIColor colorWithRed:0.5 green:0.5 blue:0.5 alpha:0.5].CGColor;;
	rocket.redRange = 0.5;
	rocket.greenRange = 0.5;
	rocket.blueRange = 0.5;

	//Name the cell so that it can be animated later using keypath
	[rocket setName:@"rocket"];

	//Flare particles emitted from the rocket as it flys
	CAEmitterCell *flare = [CAEmitterCell emitterCell];
	flare.contents = img;
	flare.emissionLongitude = (4 * M_PI) / 2;
	flare.scale = 0.4;
	flare.velocity = 100;
	flare.birthRate = 45;
	flare.lifetime = 1.5;
	flare.yAcceleration = -350;
	flare.emissionRange = M_PI / 7;
	flare.alphaSpeed = -0.7;
	flare.scaleSpeed = -0.1;
	flare.scaleRange = 0.1;
	flare.beginTime = 0.01;
	flare.duration = 0.7;

	//The particles that make up the explosion
	CAEmitterCell *firework = [CAEmitterCell emitterCell];
	firework.contents = img;
	firework.birthRate = 3000;
	firework.scale = 0.6;
	firework.velocity = 90;
	firework.lifetime = 2;
	firework.alphaSpeed = -0.2;
	firework.yAcceleration = 80;
	firework.beginTime = 1.1;
	firework.duration = 0.1;
	firework.emissionRange = 2 * M_PI;
	firework.scaleSpeed = -0.1;
	firework.spin = 2;

	//Name the cell so that it can be animated later using keypath
	[firework setName:@"firework"];

	//preSpark is an invisible particle used to later emit the spark
	CAEmitterCell *preSpark = [CAEmitterCell emitterCell];
	preSpark.birthRate = 80;
	preSpark.velocity = firework.velocity * 0.70;
	preSpark.lifetime = 1.7;
	preSpark.yAcceleration = firework.yAcceleration * 0.85;
	preSpark.beginTime = firework.beginTime - 0.2;
	preSpark.emissionRange = firework.emissionRange;
	preSpark.greenSpeed = 100;
	preSpark.blueSpeed = 100;
	preSpark.redSpeed = 100;

	//Name the cell so that it can be animated later using keypath
	[preSpark setName:@"preSpark"];

	//The 'sparkle' at the end of a firework
	CAEmitterCell *spark = [CAEmitterCell emitterCell];
	spark.contents = img;
	spark.lifetime = 0.05;
	spark.yAcceleration = -250;
	spark.beginTime = 0.8;
	spark.scale = 0.4;
	spark.birthRate = 10;

	preSpark.emitterCells = [NSArray arrayWithObjects:spark, nil];
	rocket.emitterCells = [NSArray arrayWithObjects:flare, firework, preSpark, nil];
	self.mortor.emitterCells = [NSArray arrayWithObjects:rocket, nil];
	[self.rootLayer addSublayer:mortor];
    
    [self.layer addSublayer: self.rootLayer];
}

- (void) dealloc
{
    [self.fireworkTimer invalidate];
    self.fireworkTimer = nil;
}

@end