# Monthly Archives: November 2008

## 3D Shape

Actionscript:
1. stage.frameRate = 30;
2. var centerX:Number = 200, centerY:Number = 200, zpos:Number, xpos:Number, ypos:Number, depth:Number;
3. var rotX:Number = 0, rotY:Number = 0, px:Number, py:Number, pz:Number;
4. var cosx:Number, cosy:Number, sinx:Number, siny:Number;
5.
6. var canvas:BitmapData = new BitmapData(400,400,true,0xFF000000);
8.
10.
11. function onLoop(evt:Event):void {
12.     canvas.fillRect(canvas.rect, 0xFF000000);
13.      rotX += (mouseX / 50 - rotX)/12;
14.      rotY += (mouseY / 50 - rotY)/12;
15.
16.      cosx = Math.cos(rotX);
17.      cosy = Math.cos(rotY);
18.      sinx = Math.sin(rotX);
19.      siny = Math.sin(rotY);
20.      for (var a:Number =0; a <6.28; a+=.1){
21.           for (var b:Number =0; b <6.28; b+=.05){
22.               px = 100 * Math.cos(a) * Math.cos(b) * Math.cos(b);
23.               py = 100 * Math.sin(a) * Math.cos(b)
24.               pz = 100 * Math.sin(b);
25.               zpos= pz*cosx - px*sinx  ;
26.               xpos= pz*sinx +px*cosx  ;
27.               ypos= py*cosy - zpos*siny  ;
28.               zpos= py*siny+ zpos*cosy ;
29.               depth = 1/((zpos/340)+1);
30.               canvas.setPixel((xpos * depth) + centerX, (ypos * depth) + centerY, 0xFFFFFF);
31.           }
32.      }
33. }

Renders a rotating 3D shape.

Posted in BitmapData, setPixel | Tagged , , | 5 Comments

## Simple Particles

Actionscript:
1. stage.frameRate = 30;
3. function onLoop(evt:Event):void{
4.     if (int(Math.random()*5)==1){
5.       for (var i:int= 0; i<10; i++) createParticle();
6.     }
7. }
8.
9. function createParticle():void{
10.     var s:MovieClip = new MovieClip();
11.     s.graphics.beginFill(0);
12.     s.graphics.drawCircle(0,0,Math.random()*10 + 2);
13.     s.velX = Math.random()*10-5
14.     s.velY =  Math.random()*10-5
15.     s.posX = s.x = 200;
16.     s.posY = s.y = 200;
19. }
20.
21. function onRunParticle(evt:Event):void {
22.     var s:MovieClip = MovieClip(evt.currentTarget);
23.     s.posX += s.velX;
24.     s.posY += s.velY;
25.     s.scaleX = s.scaleY -=  .04;
26.     if (s.scaleX <0){
27.         removeChild(s);
28.         s.removeEventListener(Event.ENTER_FRAME, onRunParticle);
29.     }
30.     s.x = s.posX;
31.     s.y = s.posY;
32. }

Nothing special here. But my students are always asking me about this - in class I have them alter this code to make fire, water and abstract particle systems.

Posted in motion, random | | 6 Comments

## Dynamic Timeline Vars

Actionscript:
1. this.myVar = "I am a dynamic variable";
2. trace(this.myVar);
3.
4. // trace(myVar) // will cause an error

This code will add dynamic untyped variables to the timeline. Although this example is pretty useless, it scratches the surface of an interesting topic.... by default all flash timeline code gets compiled into a giant dynamic document class that uses the undocumented addFrameScript() function. This means that all import statements on the timeline, even ones not on frame one become part of this large document class.

Posted in timeline, variables | Tagged , , | 2 Comments

## Recursion Trick w/ setTimeout()

Actionscript:
1. var counter:int = 0;
2.
3. graphics.lineStyle(0,0x000000);
4.
5. recursive();
6.
7. function recursive():void{
8.
9.     if (counter <4000){
10.        graphics.moveTo(10,10);
11.        graphics.lineTo(counter, 200);
12.        counter+=4;
13.           // don't call recursive(), use setTimeout instead
14.        setTimeout(recursive,0);
15.     }else{
16.         trace(counter / 4 + " lines were drawn");
17.     }

Be careful with this one, if you don't know what your doing you may be able to crash flash.

Anyway... if you use a recursive function in flash you may find yourself getting a stack overflow error. You can avoid this by using setTimeout():

Actionscript:
1. // don't call recursive(), use setTimeout() instead
2. setTimeout(recursive,0);

Of course... the stack overflow error is there for a reason, if used incorrectly you could bring the flash player to a standstill.

You can also achieve animated recursion by actually adding a delay to your setTimout() call:

Actionscript:
1. // don't call recursive(), use setTimeout() instead
2. setTimeout(recursive,10);