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how to add particles using SpriteKit in iOS7

I'd like to add a particle to my SpriteKit app, but I can't find how to do it. I'm able to create using the particle editor, but how do I add them to my view?

Thanks a lot in advance!

Particle System libGDX [closed]

Can anyone give me a good example of where to start with making a particle system in libGDX? I have looked at the test example in the libGDX source but I am still having trouble getting my head around it. Maybe just a good explanation of it will help. I'm thinking I want to make some sort of explosion with a lot of colorful particles. Any help is greatly appreciated!

How do those java sand games keep track of so many particles?

Can anyone shed any light on how a program like that might be structured?

What java classes would they employ to keep track of so many particles and then check against them for things like collision detection? Particles need to know what particles they are next to, or that they're not next to anything so they can fall etc.

Here's an example, incase you're not sure what a sand game is.

particle effects?

I want to achieve particle effect when an object is found. I have relative Layout on which I have many ImageViews are Placed now when user click on the ImageViews I want some particle effect to happen ( I do not want sprite animation ). How will I achieve it ? any good reference or help ?

How do you stop a particle effect? (SKEmitterNode)

I currently have this code in a collide statement where if collide with object then this particle happens but how do I stop it? As it goes on forever whereas I only want to happen a couple of times per contactetc

SKEmitterNode *emitter =  [NSKeyedUnarchiver unarchiveObjectWithFile:[[NSBundle mainBundle]     pathForResource:@"ff" ofType:@"sks"]];
emitter.zPosition = 0;
emitter.particlePositionRange = CGVectorMake(0, self.size.height);
emitter.position = CGPointMake(self.size.width, self.size.height/2);
[self addChild:emitter];

Efficient particle system in javascript? (WebGL)

I'm trying to write a program that does some basic gravity physics simulations on particles. I initially wrote the program using the standard Javascript graphics (with a 2d context), and I could get around 25 fps w/10000 particles that way. I rewrote the tool in WebGL because I was under the assumption that I could get better results that way. I am also using the glMatrix library for vector math. However, with this implementation I'm getting only about 15fps with 10000 particles.

I'm currently an EECS undergrad and I have had a reasonable amount of experience programming, but never with graphics, and I have little clue as to how to optimize Javascript code. There is a lot I don't understand about how WebGL and Javascript work. What key components affect performance when using these technologies? Is there a more efficient data structure to use to manage my particles (I'm just using a simple array)? What explanation could there be for the performance drop using WebGL? Delays between the GPU and Javascript maybe?

Any suggestions, explanations, or help in general would be greatly appreciated.

I'll try to include only the critical areas of my code for reference.

Here is my setup code:

gl = null;
try {
    // Try to grab the standard context. If it fails, fallback to experimental.
    gl = canvas.getContext("webgl") || canvas.getContext("experimental-webgl");
    gl.viewportWidth = canvas.width;
    gl.viewportHeight = canvas.height;
}
catch(e) {}

if(gl){
        gl.clearColor(0.0,0.0,0.0,1.0);
        gl.clearDepth(1.0);                 // Clear everything
        gl.enable(gl.DEPTH_TEST);           // Enable depth testing
        gl.depthFunc(gl.LEQUAL);            // Near things obscure far things

        // Initialize the shaders; this is where all the lighting for the
        // vertices and so forth is established.

        initShaders();

        // Here's where we call the routine that builds all the objects
        // we'll be drawing.

        initBuffers();
    }else{
        alert("WebGL unable to initialize");
    }

    /* Initialize actors */
    for(var i=0;i<NUM_SQS;i++){
        sqs.push(new Square(canvas.width*Math.random(),canvas.height*Math.random(),1,1));            
    }

    /* Begin animation loop by referencing the drawFrame() method */
    gl.bindBuffer(gl.ARRAY_BUFFER, squareVerticesBuffer);
    gl.vertexAttribPointer(vertexPositionAttribute, 2, gl.FLOAT, false, 0, 0);
    requestAnimationFrame(drawFrame,canvas);

The draw loop:

function drawFrame(){
    // Clear the canvas before we start drawing on it.
    gl.clear(gl.COLOR_BUFFER_BIT);

    //mvTranslate([-0.0,0.0,-6.0]);
    for(var i=0;i<NUM_SQS;i++){
        sqs[i].accelerate();
        /* Translate current buffer (?) */
        gl.uniform2fv(translationLocation,sqs[i].posVec);
        /* Draw current buffer (?) */;
        gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
    }
    window.requestAnimationFrame(drawFrame, canvas);
}

Here is the class that Square inherits from:

function PhysicsObject(startX,startY,size,mass){
    /* Class instances */
    this.posVec = vec2.fromValues(startX,startY);
    this.velVec = vec2.fromValues(0.0,0.0);
    this.accelVec = vec2.fromValues(0.0,0.0);
    this.mass = mass;
    this.size = size;

    this.accelerate = function(){
            var r2 = vec2.sqrDist(GRAV_VEC,this.posVec)+EARTH_RADIUS;
            var dirVec = vec2.create();
            vec2.set(this.accelVec,
                G_CONST_X/r2,
                G_CONST_Y/r2
            );

        /* Make dirVec unit vector in direction of gravitational acceleration */
        vec2.sub(dirVec,GRAV_VEC,this.posVec)
        vec2.normalize(dirVec,dirVec)
        /* Point acceleration vector in direction of dirVec */
        vec2.multiply(this.accelVec,this.accelVec,dirVec);//vec2.fromValues(canvas.width*.5-this.posVec[0],canvas.height *.5-this.posVec[1])));

        vec2.add(this.velVec,this.velVec,this.accelVec);
        vec2.add(this.posVec,this.posVec,this.velVec);
    };
}

These are the shaders I'm using:

 <script id="shader-fs" type="x-shader/x-fragment">
        void main(void) {
        gl_FragColor = vec4(0.7, 0.8, 1.0, 1.0);
        }
    </script>

    <!-- Vertex shader program -->

    <script id="shader-vs" type="x-shader/x-vertex">
        attribute vec2 a_position;

        uniform vec2 u_resolution;

        uniform vec2 u_translation;

        void main() {
        // Add in the translation.
        vec2 position = a_position + u_translation;
        // convert the rectangle from pixels to 0.0 to 1.0
        vec2 zeroToOne = position / u_resolution;

        // convert from 0->1 to 0->2
        vec2 zeroToTwo = zeroToOne * 2.0;

        // convert from 0->2 to -1->+1 (clipspace)
        vec2 clipSpace = zeroToTwo - 1.0;

        gl_Position = vec4(clipSpace*vec2(1,-1), 0, 1);
        }
    </script>

I apologize for this being long-winded. Again, any suggestions or nudges in the right direction would be huge.

libgdx: Is there a way to "fast-forward" particle effects?

I've worked with Game Maker previously to using libgdx, and one thing you could do is skip ahead in a particle's animation. For instance, if you have a snow particle effect, when you enter a room the snow particles would only just begin falling. But if you used the part_system_update() method repeatedly upon entering the room, you could "fast-forward" the effect, making it appear as if the snow had been falling before you entered the room. Is there a way to achieve that same result in libgdx?

Simple particle system on Android using OpenGL ES 1.0

I'm trying to put a particle system together in Android, using OpenGL. I want a few thousand particles, most of which will probably be offscreen at any given time. They're fairly simple particles visually, and my world is 2D, but they will be moving, changing colour (not size - they're 2x2), and I need to be able to add and remove then.

I currently have an array which I iterate through, handling velocity changes, managing lifecyling (killing old ones, adding new ones), and plotting them, using glDrawArrays. What OpenGl is pointing at, though, for this call, is a single vertex; I glTranslatex it to the relevant co-ords for each particle I want to plot, one at a time, set the colour with glColor4x then glDrawArrays it. It works, but it's a bit slow and only works for a few hundred particles. I'm handling the clipping myself.

I've written a system to support static particles which I have loaded into a vertex/colourarray and plot using glDrawArrays, but this approach only seems suitable for particles which will never change relative location (ie I move all of them using glTranslate), colour and where I don't need to add/remove particles. A few tests on my phone (HTC Desire) suggest that trying to alter the contents of those arrays (which are ByteBuffers, pointed to by OpenGL) is extremely slow.

Perhaps there's some way of manually writing the screen myself with the CPU. If I'm just plotting 1x1/2x2 dots on the screen, and I'm purely interested in writing and not doing any blending/antialiasing, is this an option? Would it be quicker than whatever OpenGl is doing?

(200 or so particles on a 1ghz machine with megs of ram. This is way slower than I was getting 20 years ago on a 7mhz machine with <500k of ram! I appreciate I'm using Java here, but surely there must be a better solution. Do I have to use the NDK to get the power of C++, or is what I'm after possible)

Uncaught TypeError: Cannot read property 'getContext' of null

In my console I get the error: "Uncaught TypeError: Cannot read property 'getContext' of null" and I just can't find the error I've made... or what I've done wrong. So maybe you can help me find it? Please help :)

enter code here

var canvas = document.getElementById("myCanvas");

var ctx = canvas.getContext("2d");

var cW = canvas.width = 1000; 
var cH = canvas.height = 500; 

var particleAmount = 10; 
var particles = []; 

for(var i=0;i<particleAmount;i++) { 
particles.push(new particle());

}

function particle() { 
this.x = (Math.random() * (cW-(40*2))) + 40; 
this.y = (Math.random() * (cH-(40*2))) + 40; 
this.xv = Math.random()*20-10; 
this.yv = Math.random()*20-10; 

}

function draw () { 
ctx.fillStyle = "black";
ctx.fillRect(0,0,cW,cH);

for(var ii=0;ii<particles.length;ii++){
    var p = particles[ii]; 
    ctx.fillStyle = "red";
    ctx.beginPath(); 
    ctx.arc(p.x,p.y,40,Math.PI*2,false); 
    ctx.fill();
}


}

setInterval(draw,30);

How can I create a random simulation?

I've been playing this flash game and after I'd gotten over the initial ('lol, fire') reaction I started to wonder how I could replicate this contact-mutate behaviour in programming. I guess it's a little like the honeypot xkcd.

I was thinking of starting with a scenario where particles deflect off each other and the containing walls. The sequence would start with a set number of 'mutant' particles, and when these mutants collide with regular particles they'd become mutants themselves. I could work in some more fun things later.

My problem is how to get started with this. I'm planning to do it in C# using the Drawing elements of .NET (although I'm fairly new to C# - if there's a different part of .NET I should use let me know) but if there's any general papers on it I'd be interested to read them (if they're available online of course).

Thanks, Ross

cocos2d starting particles from a specific time in the future

I am developing a cocos2d based app with a space background in which I am exploiting a CCQuadParticleSystem to make blinking stars. I have generated this particle system with ParticleDesigner. As soon as I load the particle system white dots representing stars start appearing in the background and after a while they fade out so that, after few seconds in which the particle system reaches the regime state, a night sky full of stars comes out.

My problem is that I would like to know if there is a way to make the particle system starting from a specific time in the future (for instance t0 = 3sec) so that I do not have to wait to have all the starts blinking.

I hope I have clearly explained the problem

thank you in advance

Andrea

opengl modelling rocket flame and vapour trails with particles

Does anyone have any guidance for coding an approximation for the particle stream coming out of a jet engine (with afterburner) in opengl using particles drawing using vertex buffers / 4f color buffers?

I believe there are two aspects to this problem:

1. The colour of the light as particles exit the jet engine as a function of temperature and some constants relating to the type of gas being burnt. This article leads me to believe I will need some sort of array for the temperature / color conversion curve. Apprently hydrogen burns at 2,660C in oxygen and 2,045C in air whereas jet fuel burns at 287.5C in air. (but the temperature of jet fighter afterburner can reach 1700C somehow)

2. The vapour trail behind the rocket / jet which will be either white with alpha for the water base vapour trail if the rocket is in atmosphere. Also I believe my assumption is correct that this would not be necessary for a rocket burning fuel in space. The vapour trail will simulated as tiny water droplets which are much larger than the wavelength of visible light, so they would scatter light achromatically. As water itself is colorless the resulting color would be white?

Also I am looking to model this from a birds eye perspective so it does not need to be a full 3D model. So the positions of the 10 or so pilot lights around the afterburner cone for example could just be approximated as maybe 5 linear points.

Simulating a candle flame in Objective C

As part of a current project I've been asked to display a candle onscreen. Users should be able to tilt the device to tilt the flame, and perform an action (eg. tap) to blow out the flame. I'm at a real loss on how to achieve this. Some ideas I've had:

• purchase a movie of a candle from a stock video site. This won't let me tilt or blow out the flame though
• obtain a number of frames and animate them to give the appearance of a flickering flame
• use some form of particle emitter

I guess my preference would probably be to use the particle emitter, as I can't see the video working and getting the necessary assets for the frame animation could be a problem. I know Cocos2D has a particle emitter, but this is part of a larger UIKit project which can't be ripped apart and started again to build on top of Cocos2D.

Does anyone have any ideas on how I can achieve this?

particle system: particle generation

I have a system that generates particles from sources and updates their positions. Currently, I have written a program in OpenGL which calls my GenerateParticles(...) and UpdateParticles(...) and displays my output. One functionality that I would like my system to have is being able to generate n particles per second. In my GenerateParticles(...) and UpdateParticles(...) functions, I accept 2 important parameters: current_time and delta_time. In UpdateParticles(...), I update the position of my particle according to the following formula: new_pos = curr_pos + delta_time*particle_vector. How can I use these parameters and global variables (or other mechanisms) to produce n particles per second?

What STL container to perform removal of elements in between?

I need to pick a container to hold pointers to a type I defined (Particle). I'm using a pre-allocated Particle Object Pool ( which contain objects pre-allocated on an std::vector ).

My Particle emitters ask the Particle Pool for particles when they need to emit, ( in order to avoid in-game Particle allocation ). When a Particle expires, it is returned to the Particle Object Pool.

As you can see, as I iterate through my Particle Reference Container (need to pick one) in order to update it, I will have to check which particles have expired (lifetime <= 0.0) and return them back to the Particles Pool, the expired particles could be at any position in the container.

I've been thinking about using std::list, here's why:

A list (AFAIK) provides constant time insertion at the beginning , and constant time removal at any point ( assuming you have iterated to that point ).

Any suggestions or improvements to my system in order to better accomodate your container suggestions are welcome.

EDIT:

To explain myself a bit better:

The life time of the particles in an emitter is not exactly the same, it depends on a range, for example, 5.0 seconds +- (0.0 to 0.5). This is in order to give the particles a randomness element, and looks quite better than all in fixed time.

Algorithm Pseudo code:

    // Assume typedef std::container_type<Particle *> ParticleContainer

void update(float delta)
{   
    ParticleContainer::iterator particle = m_particles.begin();   

    for(; particle != m_particles.end(); ++particle)
    {
        updateParticle(*particle, delta);         //Update the particle

        if ( (*particle)->lifeTime <= 0.0 )
        {
            ParticlePool.markAsFree(*particle);   //Mark Particle as free in the object Pool
            m_particles.remove(*particle);        //Remove the Particle from my own ParticleContainer
        }   
    }
}