QuickBox2D addTimeStepSequence() Preview

By Zevan | September 11, 2009
CLICK HERE TO COPY
Actionscript:
  1. import com.actionsnippet.qbox.*;
  2.  
  3. [SWF(width = 800, height = 600, backgroundColor = 0xFFFFFF, frameRate=60)]
  4.  
  5. // hide everything for 300 ms
  6. visible = false;
  7. setTimeout(function():void{ visible = true}, 300);
  8.  
  9. var canvas:MovieClip = MovieClip(addChild(new MovieClip()));
  10.  
  11. var sim:QuickBox2D = new QuickBox2D(canvas, {debug:true});
  12.  
  13. sim.setDefault({fillColor:0x666666, lineAlpha:0})
  14. sim.createStageWalls();
  15.  
  16. var boxA:QuickObject = makeLever(6 , 17.5, 9, "right", 0.7);
  17. var circleA:QuickObject = sim.addCircle({x:2, y:3, radius:0.5, mass:4});
  18. sim.addBox({x:15, y:12, width:2, height:0.5, density:0})
  19. var circleB:QuickObject = sim.addCircle({x:16, y:11, radius:0.5, mass:4, friction:0.2, fillColor:0});
  20. sim.addBox({x:20.5, y:12, width:2, height:0.3, angle:-0.6, restitution:4.6, density:0})
  21. var boxB:QuickObject = makeLever(20 , 17.5, 8, "right", 1);
  22. sim.addBox({x:9, y:9, width:2, height:0.5, density:0});
  23. var circleC:QuickObject = sim.addCircle({x:9, y:9, radius:0.5, mass:4, friction:0.2, fillColor:0});
  24. sim.addBox({x:7, y:12, width:2, height:0.5, angle:-0.3, density:0, restitution:2});
  25. sim.addBox({x:3, y:7, width:2, height:0.5, angle:Math.PI/2 - 0.22, density:0, restitution:3});
  26. sim.addBox({x:13, y:15, width:2, height:0.5, density:0, angle:0.3, restitution:1});
  27. sim.addBox({x:25.5, y:7, width:2, height:0.3, angle:-0.2, restitution:0.5, density:0})
  28. sim.addBox({x:26, y:10, width:1, height:1, density:0,restitution:0.3});
  29. sim.addBox({x:25, y:19, width:2, height:0.5, density:0, restitution:3.5, angle:-0.99});
  30. sim.addBox({x:1, y:17, width:0.3, height:2, density:0, angle:-0.15, restitution:0.999});
  31. sim.addBox({x:0.7, y:11, width:0.3, height:2, density:0, angle:-0.19, restitution:20})
  32. sim.addBox({x:0.4, y:11.5, width:1, height:0.3, density:0})
  33.  
  34. function makeLever(xp:Number, yp:Number, boxWidth:Number, dir:String, off:Number=0, hasBox:Boolean=true):QuickObject{
  35.     var angle:Number, xpos:Number, weight:QuickObject
  36.     if (dir == "right"){
  37.         angle = 0.43;
  38.         xpos = xp + boxWidth / 2 - off;
  39.     }else{
  40.         angle = -0.43;
  41.         xpos = xp - boxWidth / 2 + off;
  42.     }
  43.     if (hasBox){
  44.       weight = sim.addBox({x:xpos , y:yp, width:0.5, height:0.5, angle:angle, fillColor:0});
  45.     }
  46.     var plank:QuickObject = sim.addBox({x:xp, y:yp, width:boxWidth, height:0.5, angle:angle});
  47.     var fulcrum:QuickObject = sim.addPoly({x:xp, y:yp, verts:[[0,0, 1,2, -1,2]], density:0})
  48.     sim.addJoint({type:"revolute", a:plank.body, b:fulcrum.body, collideConnected:false});
  49.     return weight;
  50. }
  51.  
  52. sim.start();
  53.  
  54. // new feature, calls a function after a specific number of box2D timeSteps
  55. sim.addTimeStepSequence({time:70, callback:cam, args:[boxA]},
  56.                         {time:150, callback:cam, args:[circleB]},
  57.                         {time:200, callback:cam, args:[boxB, 1.3]},
  58.                         {time:580, callback:cam, args:[circleC]},
  59.                         {time:700, callback:cam, args:[circleC, 1.1]},
  60.                         {time:810, callback:cam, args:[boxB, 1.4]},
  61.                         {time:870, callback:cam, args:[boxB, 3]},
  62.                         {time:890, callback:cam, args:[boxB, 1.1]},
  63.                         {time:1200,callback:cam, args:[boxB, 1]});
  64.  
  65. // set values for matrix pan and zoom
  66. function cam(quickObj:QuickObject, scale:Number=-1):void{
  67.     currQuick = quickObj;
  68.     if (scale != -1){
  69.         scaleDest = scale;
  70.     }
  71. }                                
  72.                
  73. // matrix pan and zoom
  74. var scale:Number = 1;
  75. var scaleDest:Number = 1.2;
  76. var down:Boolean = false;
  77. var dx:Number = 0, dy:Number = 0, time:Number = 0;
  78. var currQuick:QuickObject = circleA;
  79. addEventListener(Event.ENTER_FRAME, onLoop);
  80. function onLoop(evt:Event):void {
  81.    scale += (scaleDest - scale) / 8;
  82.    dx += (currQuick.x*30 - dx) / 8;
  83.    dy += (currQuick.y*30 - dy) / 8;
  84.    // matrix zoom/pan
  85.     var m:Matrix = canvas.transform.matrix;
  86.    m.identity();
  87.    m.translate(-dx,-dy);
  88.    m.scale(scale, scale);
  89.    m.translate(dx,dy);
  90.    canvas.transform.matrix = m;
  91. }

This is a preview of an upcoming feature for the QuickBox2D 1.0 release. It shows how addTimeStepSequence() is going to work. QuickBox2D 1.0 will have an internal timer counting the number of world steps that Box2D has taken. This is really useful for sequencing in conjunction with QuickBox2D's default FRIM (framerate independent motion).

This snippet uses addTimeStepSequence() to move a 2D camera around the simulation (from yesterdays post) - the camera pans and zooms... If you'd like to use addTimeStepSequence() simply replace your QuickBox2D.as file with this updated one:

I plan to release QuickBox2D 1.0 on monday - so I didn't think it made sense to do alpha 110 just for this one change...


Have a look at the swf....

This entry was posted in Box2D, QuickBox2D, motion and tagged , , , . Bookmark the permalink. Post a comment or leave a trackback: Trackback URL.

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  1. By blog.alumican.net » Blog Archive » QuickBox2D正式版v1.0リリース on October 4, 2009 at 8:54 am

    [...] 22. 指定した時間ステップ後に呼び出される関数 – QuickBox2D addTimeStepSequence() Preview [...]

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