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AS3 version of my endless starfield & parallax scrolling effect. This is a huge improvement over the last script in terms of performance and ease-of-use.

This version lets you set the width, height, and speed of the starfield, as well as position it anywhere on stage by setting the X & Y coordinates (old version only allowed it to be fullscreen).

This is great because you’ll now be able to use it in games (top-down and side scrollers), any size banners (horizontal or skyscrapers), and anywhere else you need the effect.

Using it is pretty simple: parallaxField.createField(containerMC, x, y, width, height, numberOfStars, speedX, speedY); You can also use: parallaxField.enable(); parallaxField.disable(); To start and stop the effect.

See Main.as for exact usage examples.

/** * Endless Starfield - Parallax Scrolling * --------------------- * VERSION: 1.0 * DATE: 6/26/2010 * AS3 * UPDATES AND DOCUMENTATION AT: http://www.FreeActionScript.com **/ package com. freeactionscript { import flash. display . MovieClip ; import flash. display . Sprite ; import flash. events . Event ; import flash. events . MouseEvent ; import flash. utils . getDefinitionByName ; public class ParallaxField extends MovieClip { // settings & vars private var acceleration: Number = .25; private var starBox:Sprite; private var starsArray: Array = [ ] ; private var starArrayLength: int ; private static var STAR_SMALL: String = "small" ; private static var STAR_NORMAL: String = "normal" ; private static var STAR_LARGE: String = "large" ; private var pathToContainer: MovieClip ; private var containerX: int ; private var containerY: int ; private var containerWidth: int ; private var containerHeight: int ; private var speedX: Number ; private var speedY: Number ; private var isStarted: Boolean = false ; private var _upPressed: Boolean = false ; private var _downPressed: Boolean = false ; private var _leftPressed: Boolean = false ; private var _rightPressed: Boolean = false ; /** * Creates Parallax Field * * @param $container The container that holds all our starfield assets. Must be created and added to stage before being used here. * @param $x The X position of our starfield. * @param $y The Y position of our starfield. * @param $width The width of our starfield. * @param height The height of our starfield. * @param $numberOfStars Number of stars to create. * @param $speedX The initial X speed of our starfield. * @param $speedY The initial Y speed of our starfield. */ public function createField ( $container: MovieClip , $x: int , $y: int , $width: int , $height: int , $numberOfStars: int , $speedX: int , $speedY: int ) : void { trace ( "createField" ) ; // save property references pathToContainer = $container; containerX = $x; containerY = $y; containerWidth = $width; containerHeight = $height; speedX = $speedX; speedY = $speedY; // create everything createStarBox ( ) ; addStars ( $numberOfStars, "small" ) ; addStars ( $numberOfStars, "normal" ) ; addStars ( $numberOfStars, "large" ) ; // enable enable ( ) ; } /** * Adds stars to star container * * @param $numberOfStars Amount of stars to create */ public function addStars ( $numberOfStars: int , $type: String ) : void { trace ( "Adding stars..." ) ; var newNumberOfStars: Number ; var graphic: String ; var speedModifier: Number ; var ClassReference: Class ; // set star properties if ( $type == STAR_LARGE ) { graphic = "StarLarge" ; speedModifier = 1 ; newNumberOfStars = Math . round ( $numberOfStars * .30 ) ; } else if ( $type == STAR_NORMAL ) { graphic = "StarNormal" ; speedModifier = .66; newNumberOfStars = Math . round ( $numberOfStars * .60 ) ; } else if ( $type == STAR_SMALL ) { newNumberOfStars = Math . round ( $numberOfStars * 1 ) ; graphic = "StarSmall" ; speedModifier = .33; } trace ( " type: " + graphic ) ; trace ( " amount: " + newNumberOfStars ) ; // run a for loop to create new stars (based on numberOfStars) var i: int ; for ( i = 0 ; i < newNumberOfStars; i++ ) { // get class via string name ClassReference = getDefinitionByName ( graphic ) as Class ; // create class var tempStar: MovieClip = new ClassReference ( ) ; // set random starting position tempStar. x = ( Math . random ( ) * ( containerWidth - tempStar. width ) ) + containerX; tempStar. y = ( Math . random ( ) * ( containerHeight - tempStar. height ) ) + containerY; // give the star its own speed modifier tempStar. speedModifier = speedModifier; // add new star to array that tracks all stars starsArray. push ( tempStar ) ; // add to display list pathToContainer. addChild ( tempStar ) ; } trace ( "Stars Added \n " ) ; } /** * Activates parallax effect */ public function enable ( ) : void { if ( ! isStarted ) { trace ( "Starting parallax effect..." ) ; isStarted = true ; // add enter frame pathToContainer. addEventListener ( Event. ENTER_FRAME , gameLoop ) ; } else { trace ( "Parallax effect already running." ) ; } } /** * Disables parallax effect */ public function disable ( ) : void { if ( isStarted ) { trace ( "Stopping parallax effect..." ) ; isStarted = false ; // remove enter frame pathToContainer. removeEventListener ( Event. ENTER_FRAME , gameLoop ) ; } else { trace ( "Parallax effect is not running." ) ; } } /** * key press getters and setters */ public function get upPressed ( ) : Boolean { return _upPressed; } public function set upPressed ( value: Boolean ) : void { _upPressed = value; } public function get downPressed ( ) : Boolean { return _downPressed; } public function set downPressed ( value: Boolean ) : void { _downPressed = value; } public function get leftPressed ( ) : Boolean { return _leftPressed; } public function set leftPressed ( value: Boolean ) : void { _leftPressed = value; } public function get rightPressed ( ) : Boolean { return _rightPressed; } public function set rightPressed ( value: Boolean ) : void { _rightPressed = value; } /*************************************************************************/ /** * @private * Creates a star container */ private function createStarBox ( ) : void { trace ( "Creating star container..." ) ; trace ( " path: " + pathToContainer ) ; trace ( " x: " + containerX ) ; trace ( " y: " + containerY ) ; trace ( " width: " + containerWidth ) ; trace ( " height: " + containerHeight ) ; // create new container for stars starBox = new Sprite ( ) ; starBox. graphics . beginFill ( 0x000000 ) ; // set container's properties starBox. x = containerX; starBox. y = containerY; starBox. width = containerWidth; starBox. height = containerHeight; // create mask var starBoxMask:Sprite = new Sprite ( ) ; starBoxMask. graphics . beginFill ( 0xFF0000 ) ; starBoxMask. graphics . drawRect ( containerX, containerY, containerWidth, containerHeight ) ; pathToContainer. addChild ( starBoxMask ) ; // Apply mask starBox. mask = starBoxMask; // add starBox to stage pathToContainer. addChild ( starBox ) ; trace ( " Container Created \n " ) ; } /** * @private * This function is executed every frame. */ private function gameLoop ( event:Event ) : void { updateSpeed ( ) ; updateStars ( ) ; } /** * @private * This function updates the movement speed */ private function updateSpeed ( ) : void { if ( upPressed ) { speedY = speedY - acceleration; } else if ( downPressed ) { speedY += acceleration; } if ( rightPressed ) { speedX += acceleration; } else if ( leftPressed ) { speedX -= acceleration; } } /** * @private * This function updates all the objects in the stars array */ private function updateStars ( ) : void { // setting the array length variable outside of the for loop improves speed starArrayLength = starsArray. length ; // setting the "tempStar" variable outside of the for loop improves speed var tempStar: MovieClip ; // setting the "i" variable outside of the for loop improves speed var i: int ; // run for loop for ( i = 0 ; i < starArrayLength; i++ ) { tempStar = starsArray [ i ] ; tempStar. x += speedX * tempStar. speedModifier ; tempStar. y += speedY * tempStar. speedModifier ; //Star boundres //check X boudries if ( tempStar. x > = containerWidth - tempStar. width + containerX ) { //outside boundry, move to other side of container tempStar. x = containerX; tempStar. y = ( Math . random ( ) * ( containerHeight - tempStar. height ) ) + containerY; } else if ( tempStar. x < = containerX ) { //outside boundry, move to other side of container tempStar. x = containerWidth + containerX - tempStar. width ; tempStar. y = ( Math . random ( ) * ( containerHeight - tempStar. height ) ) + containerY; } //check Y boudries if ( tempStar. y > = containerHeight - tempStar. height + containerY ) { //outside boundry, move to other side of container tempStar. x = ( Math . random ( ) * ( containerWidth - tempStar. width ) ) + containerX; tempStar. y = containerY; } else if ( tempStar. y < = containerY ) { //outside boundry, move to other side of container tempStar. x = ( Math . random ( ) * ( containerWidth - tempStar. width ) ) + containerX; tempStar. y = containerHeight + containerY - tempStar. height ; } } } } }

Download Fla Sample

I know this script is not perfect. I might update it in the near future to use bitmaps instead of movieclips, among other things.

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