Category Archives: motion

Not a Snippet (wandering robots)

Actionscript:
  1. package {
  2.     import flash.display.Sprite;
  3.    
  4.     [SWF(width=500, height=500, backgroundColor=0xEFEFEF, frameRate=30)]
  5.     public class Main extends Sprite{
  6.         private var _robotManager:RobotManager;
  7.         public function Main(){
  8.           _robotManager = new RobotManager(this, 12);
  9.         }
  10.     }
  11. }
  12.  
  13. class RobotManager{
  14.    
  15.     private var _robots:Array;
  16.     private var _top:Sprite;
  17.     private var _robotNum:int;
  18.    
  19.     public function RobotManager(top:Sprite, robotNum:int){
  20.         _top = top;
  21.         _robotNum = robotNum;
  22.         _robots = new Array();
  23.         setupRobots();
  24.         top.addEventListener(Event.ENTER_FRAME, onRun);
  25.     }
  26.    
  27.     private function setupRobots():void{
  28.         for (var i:int = 0; i<_robotNum; i++){
  29.             _robots[i] = new Robot();
  30.             _robots[i].x = 100+(i % 3) * 150;
  31.             _robots[i].y = 100+int(i / 3) * 100;
  32.             _robots[i].addEventListener("death", onRobotDie);
  33.             _top.addChild(_robots[i]);
  34.         }
  35.     }
  36.     private function onRobotDie(evt:Event):void{
  37.         for (var i:int = 0; i<_robotNum; i++){
  38.             if (_robots[i] == evt.currentTarget){
  39.                 _robots.splice(i, 1);
  40.             }
  41.         }
  42.         _robotNum--;
  43.     }
  44.    
  45.     private function onRun(evt:Event):void{
  46.         collisions();
  47.     }
  48.    
  49.     private function collisions():void{
  50.         var currBot:Robot;
  51.         for (var i:int = 0; i<_robotNum; i++){
  52.             currBot = _robots[i];
  53.             for (var j:int = 0; j<_robotNum; j++){
  54.                 if (currBot != _robots[j]){
  55.                     var dx:Number = currBot.x - _robots[j].x;
  56.                     var dy:Number = currBot.y - _robots[j].y;
  57.                     if (Math.sqrt((dx * dx) + (dy * dy)) <40){
  58.                         currBot.die();
  59.                     }
  60.                 }
  61.             }
  62.         }
  63.     }
  64. }
  65.  
  66. import flash.display.*
  67. import flash.events.*;
  68.  
  69. class Robot extends Sprite{
  70.     private var _inc:Number
  71.     private var _td:Number;
  72.     private var _theta:Number;
  73.     private var _rad:Number;
  74.    
  75.     public function Robot(){
  76.         _theta = Math.random() * (Math.PI * 2);
  77.         _td = _theta;
  78.         _inc = Math.random() * .2 + .05;
  79.         _rad = _inc * 10;
  80.         with(graphics){
  81.             beginFill(0x666666);
  82.             drawRect(-10,-10,20,20);
  83.             endFill();
  84.             beginFill(0x333333);
  85.             drawRect(-5, -5, 20, 10);
  86.             lineStyle(0,0xAAAAAA);
  87.             endFill();
  88.             drawCircle(0,0,20);
  89.         }
  90.         addEventListener(Event.ENTER_FRAME, onRun);
  91.     }
  92.    
  93.     private function onRun(evt:Event):void{
  94.         _td  += _inc;
  95.         _theta += _inc * Math.cos(_td);
  96.         if (x <0 || y <0 || x> 500 || y> 500){
  97.             _theta += Math.PI;
  98.         }
  99.         x += _rad * Math.cos(_theta);
  100.         y += _rad * Math.sin(_theta);
  101.         rotation = _theta / Math.PI * 180;
  102.     }
  103.    
  104.     public function die():void{
  105.         removeEventListener(Event.ENTER_FRAME, onRun);
  106.         addEventListener(Event.ENTER_FRAME, onDie);
  107.     }
  108.    
  109.     private function onDie(evt:Event):void{
  110.         scaleX = scaleY += .1;
  111.         alpha -= .1;
  112.         if (scaleX> 2){
  113.             removeEventListener(Event.ENTER_FRAME, onDie);
  114.             if (parent){
  115.                 parent.removeChild(this);
  116.                 dispatchEvent(new Event("death"));
  117.             }
  118.         }
  119.     }
  120. }

This code should be placed in a document class... not the timeline (hopefully you already know that)

The above creates 12 wandering robots that die when they collide with one another.

This is not a snippet really... but it's only slightly over 100 lines and it contains a few tricks I find myself using from time to time.

You can view the swf here.

Also posted in Events, OOP, arrays | Tagged , , | 3 Comments

Animate Along Bezier Curve

Actionscript:
  1. var circle:Shape = Shape(addChild(new Shape));
  2. with(circle.graphics) beginFill(0x000000), drawCircle(0,0,5);
  3.  
  4. var bezierPoint:Point = new Point();
  5. function bezier(a:Number, x1:Number, y1:Number, x2:Number, y2:Number, x3:Number, y3:Number):void {
  6.         var b:Number =1-a;
  7.         var pre1:Number=a*a;
  8.         var pre2:Number=2*a*b;
  9.         var pre3:Number=b*b;
  10.         bezierPoint.x = pre1*x1 + pre2*x2  + pre3*x3;
  11.         bezierPoint.y = pre1*y1 + pre2*y2 + pre3*y3;
  12. }
  13.  
  14. var inc:Number = 0;
  15. var theta:Number = 0;
  16.  
  17. addEventListener(Event.ENTER_FRAME, onLoop);
  18. function onLoop(evt:Event):void {
  19.    
  20.      graphics.clear();
  21.      graphics.lineStyle(0,0xFF0000);
  22.      graphics.moveTo(200,200);
  23.      graphics.curveTo(mouseX, mouseY, 400, 200);
  24.  
  25.     theta+= .05;
  26.     inc = .5 + .5*Math.sin(theta);
  27.  
  28.     bezier(inc, 200, 200, mouseX, mouseY, 400, 200);
  29.     circle.x = bezierPoint.x;
  30.     circle.y = bezierPoint.y;
  31. }

The above animates a circle along a quadratic bezier curve. This snippet was written in response to a question spurned by some of the recent bezier posts. I used Math.sin() to animate the circle but you could just as easily use modulus... simply replace lines 25-26 with the following:

Actionscript:
  1. inc += .03;
  2. inc %= 1;

Also posted in Graphics, bezier, graphics algorithms | Tagged , | 3 Comments

Glitch Auto-asteroids

Actionscript:
  1. [SWF(width=600, height=400, backgroundColor=0x000000, frameRate=30)]
  2. // make some ships
  3. for (var i:int = 0; i<10; i++) makeShip();
  4. //
  5. function makeShip():void {
  6.     // setup vars
  7.     var char:Object ={posX:Math.random()*stage.stageWidth, posY:Math.random()*stage.stageHeight, velX:0, velY:0, rad:4, theta:Math.random()*6.28, thetaDest:Math.random()*6.28, mc: MovieClip(addChild(new MovieClip()))}
  8.     // draw and position the char
  9.     with(char.mc) graphics.lineStyle(0,0xFFFFFF), graphics.moveTo(-15, -5), graphics.lineTo(0, 0), graphics.lineTo(-15, 5), x=char.posX, y=char.posY;
  10.     // loop
  11.     addEventListener(Event.ENTER_FRAME, function(){
  12.         // change position based on velocity, .9 friction
  13.         with (char) posX += velX *= .9, posY += velY *= .9;
  14.         // randomize radius and theta
  15.         if (int(Math.random()*10) == 1) char.thetaDest += Math.random()*2-1;
  16.         if (int(Math.random()*90) == 1) char.rad = Math.random()*4 + 4
  17.         // apply changes to velocity
  18.         char.theta += (char.thetaDest - char.theta) / 12;
  19.         char.velX = char.rad * Math.cos(char.theta);
  20.         char.velY = char.rad * Math.sin(char.theta);
  21.         // screen bounds
  22.         if (char.posX> 620) char.posX = -20;
  23.         if (char.posX <-20) char.posX = 620;
  24.         if (char.posY> 420) char.posY = -20;
  25.         if (char.posY <-20) char.posY = 420;
  26.         // rotation
  27.         char.mc.rotation = (Math.abs(char.mc.y - char.posY)>.7 || Math.abs(char.mc.x - char.posX)> .7) ?  Math.atan2(char.posY - char.mc.y,char.posX -  char.mc.x) / Math.PI * 180 : char.mc.rotation;
  28.         // shoot
  29.         if(int(Math.random()*100) <20) shootBullet(char, 5 * Math.cos(char.mc.rotation * Math.PI / 180)+ char.velX, 5 * Math.sin(char.mc.rotation * Math.PI / 180) + char.velY);
  30.         // apply position
  31.         with(char) mc.x = posX, mc.y = posY;
  32.         });
  33. }
  34. //
  35. function shootBullet(char:Object, vx:Number, vy:Number):void{
  36.     var b:MovieClip = MovieClip(addChild(new MovieClip()));
  37.     b.life = 0;
  38.     with(b) graphics.beginFill(0xFFFFFF), graphics.drawCircle(0,0,2), x = char.mc.x, y = char.mc.y;
  39.     b.addEventListener(Event.ENTER_FRAME, function(){
  40.             with (b) x += vx, y += vy, life++;
  41.             if (b.life> 30) b.removeEventListener(Event.ENTER_FRAME, arguments.callee), removeChild(b);
  42.     });
  43. }

An asteroids inspired code snippet. See the swf here.

Also posted in misc | Tagged , | Leave a comment

Zeno’s [classic easeOut]

Actionscript:
  1. stage.frameRate = 30;
  2. var circle:Shape = Shape(addChild(new Shape()));
  3. with(circle.graphics) beginFill(0x000000), drawCircle(0,0,10);
  4. circle.y = 50;
  5.  
  6. addEventListener(Event.ENTER_FRAME, onLoop);
  7. function onLoop(evt:Event):void {
  8.     circle.x += (mouseX - circle.x) / 12;
  9. }

Also posted in one-liners | Tagged , | Leave a comment