flash particle system

Flash Particle Systemleonskywalker@163.com

1.Overview

A particle system usually consists of

3 parts.*

*Typical Implementation

Emitter Particle

Physics

Emitter

This is an emitter

What an emitter do:

1.emit particles.2.controls how to emit particles.

(birthrate, velocity, direction..etc).

3.holds a zone to generate particles. (can be a point, textfield or any bitmapdata using alpha mask..etc)

Uniform

Directional

Point

TextField

Particle

Particle is What is a particle?

1.What you just see(the little blocks).

2.Basic units of a particle system.

3.Usually in (really) large number.

4.Does not necessarily be small.

This is particle.

This is particle.

This is also particle!

Physics

Physics system controls the motion of every particle.

v GP( x , y )

f

aSome high-

school Physics!

Even more advanced physics

• Mutual Gravity

Even more advanced physics

Turbulence

2.Implement

Emitter Particle

Physics

Global Environmental Variables

• Gravity• Air Resistence Factor• Wind

Concrete calculation is in each particle’s loop.

Physics calculations

Emitter Particle

Physics

ParticleAttributes*

• Position• Velocity (speed and direction)• Color• Lifetime• Age• Shape• Size• Transparency

*By Siggraph

ParticleAttributes

• Position• Velocity (speed and direction)• Color• Lifetime• Age• Shape• Size• Transparency

Value Object

• Velocity• Lifetime• Age

• Position• Transparency• Color• Shape• Size

ItemRenderer

• Position• Mass• Update()

Pseudo codefunction update(){

age++;if(age > lifetime){

dispose();return;

}…calculateAcceleration(SpeedX,SpeedY);updatePosition(acceleration,oldX,oldY);…draw();

}

Uses global physics variables

Emitter Particle

Physics

• Generate and dispose particles.

• Interacting with mouse position(if needed).

• Update particles’ attributes(position, rotation, alpha..etc.).

We can put it in Emitter class

We need one major loop to

particle = new Particle() n timesn = number per frame = birthrate / frameratesetInitialAttribute(particle);

ENTER_FRAME

foreach particle in particlesArrayparticle.update();

A very basic particle system

3.Optimize

• large amount of objects are being generated.

• at the same time large amount of objects are marked for GC.

Facts #1:

Try using Object Pool.

Object Pool

Emitter

particles

Create

Trying to find an instance

Destroy

recycling to pool

create

if(pool.length >0){return pool.pop();

}else{return new Particle();

}

destroy particle.initialize();pool.push(particle);

• large amount of objects are being displayed at the same time.

Facts #2:

Try using BitmapData.

Value Object

• Velocity• Lifetime• Age

• Position• Transparency• Color• Shape• Size

ItemRenderer

• Position• Mass• Update()

Value Object

• Velocity• Lifetime• Age

• Position• Transparency• Color• Shape• Size

ItemRenderer

• Position• Mass• Update()

BitmapCanvas

Value Object

• Velocity• Lifetime• Age

ItemRenderer

• Position• Mass• Update()

BitmapCanvas

• Transparency• Color• Shape

pointbitmapdata.lock()foreach particle in particleArray

bitmapdata.setpixel32()bitmapdata.unlock();

sprite bitmapdata.draw(source,matrix, colorTransform)

bitmap Bitmapdata.copyPixels()

(No rotation and scale)

•More memory usage (compared to cacheAsBitmap=false)

•Drastic performance boostBecause we manually overrode the process of native displaying, bypassed the native rasterize engine

More speed means more effects available.

Glowing trails

Depth of Field

Advanced glow and motion blur

4.Real world use

We are looking

forward to see

your works!

Some popular open source particle enginesYou can start building your works today

http://flintparticles.org/

http://code.google.com/p/stardust-particle-engine/

Plugin StructureProvides more flexibility

addInitializer(new Color(color));

addInitializer(new Position(new SinglePoint(320, 480)));

addInitializer(new Velocity(bitmapZone));

addInitializer(new Life(new UniformRandom(120, 30)));

Initialize

var gravity:Gravity = new Gravity();

gravity.addField(new UniformField(0, 0.1));

addAction(gravity);

addAction(new Age());

addAction(new DeathLife());

addAction(new Move());

addAction(new AlphaCurve(0, 60));

Particle Behavior:

• http://mrdoob.com/lab/pv3d/dof/06/

• http://co.youa.baidu.com/content/promo/100shops7/index.html

Examples used in previous slides:

Thank you!

leonskywalker@163.comMar 2010

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