Tag Archives: QuickBox2D

QuickBox2D groupIndex Platforms

By Zevan | September 4, 2009
CLICK HERE TO COPY
Actionscript:
  1. import com.actionsnippet.qbox.*;
  2. import Box2D.Common.Math.*;
  3. import Box2D.Collision.Shapes.*;
  4.  
  5. [SWF(width = 800, height = 600, backgroundColor = 0x000000)]
  6.  
  7. var sim:QuickBox2D = new QuickBox2D(this);
  8.  
  9. sim.createStageWalls();
  10.  
  11. var boxNum:int = 8;
  12. var boxes:Array = [];
  13. var xp:Number, yp:Number, w:Number;
  14. for (var i:int = 0; i<boxNum; i++){
  15.     xp = 3 + Math.random() * 10;
  16.     yp = 4 + i * 2;
  17.     w = 2 + Math.random() * 3;
  18.     boxes.push(sim.addBox({x: xp, y: yp, width: w, height: 0.5, density:0, groupIndex:-1, fillColor:0xFF6532}));
  19. }
  20.  
  21. var char:QuickObject = sim.addBox({x:2, y:18, width:1, height:2, allowSleep:false, groupIndex:-1, fillColor:0x0099CC});
  22.  
  23. sim.start();
  24.  
  25. var charVel:b2Vec2;
  26. var charVelAng:Number;
  27.  
  28. addEventListener(Event.ENTER_FRAME, onLoop);
  29. function onLoop(evt:Event):void {
  30.      
  31.     charVel = char.body.GetLinearVelocity();
  32.     charVelAng =  char.body.GetAngularVelocity();
  33.     var filter:b2FilterData;
  34.    
  35.     if (key[Keyboard.RIGHT]){
  36.         charVel.x += 1
  37.         char.body.SetLinearVelocity(charVel);
  38.         charVelAng += 1;
  39.         char.body.SetAngularVelocity(charVelAng);
  40.     }
  41.     if (key[Keyboard.LEFT]){
  42.         charVel.x -=1;
  43.         char.body.SetLinearVelocity(charVel);
  44.         charVelAng -= 1;
  45.         char.body.SetAngularVelocity(charVelAng);
  46.     }
  47.     if (key[Keyboard.UP] && sim.w.GetContactCount()> 0){
  48.          charVel.y = -10;
  49.          trace(charVel.y);
  50.          char.body.SetLinearVelocity(charVel);
  51.          charVelAng *= 0.8;
  52.          char.body.SetAngularVelocity(charVelAng);
  53.     }
  54.     for (var i:int = 0; i<boxes.length; i++){
  55.         var rect:Rectangle = char.userData.getRect(this);
  56.         if (rect.bottom / 30 <boxes[i].y){
  57.             filter = boxes[i].shape.GetFilterData();
  58.             filter.groupIndex = 1;
  59.             boxes[i].shape.SetFilterData(filter);
  60.         }else{
  61.             filter = boxes[i].shape.GetFilterData();
  62.             if (filter.groupIndex != -1){
  63.                 filter.groupIndex = -1;
  64.                 boxes[i].shape.SetFilterData(filter);
  65.             }
  66.         }
  67.     }
  68. }
  69.  
  70. var key:Object = new Object();
  71. stage.addEventListener(KeyboardEvent.KEY_DOWN, onKeyPressed);
  72. stage.addEventListener(KeyboardEvent.KEY_UP, onKeyReleased);
  73. function onKeyPressed(evt:KeyboardEvent):void{ key[evt.keyCode] = true; }
  74. function onKeyReleased(evt:KeyboardEvent):void{ key[evt.keyCode] = false; }

NOTE: This requires the QuickBox2D mini-library

This snippet shows how to use groupIndex to create simple platforms for a character to jump on. A few people have asked me about this so I figured I'd post about it. It works by altering the groupIndex of each platform based on the characters position - if the character is below a platform, both the character and the platform have groupIndex -1 (meaning they will not collide). As soon as the character is above a platform, the platforms groupIndex is set to 1 (allowing the character to walk on the platform despite having just passed through it.


Have a look at the swf...


It's also worth noting that I'm using b2World.GetContactCount() to make sure it's ok to jump... if there were more going on in the demo you'd need to check a specific contact point(s), but since the only collision that could happen involves the character this works nicely...

Posted in Box2D, QuickBox2D | Also tagged , , , | 10 Comments

QuickBox2D Unicycler

By Zevan | August 17, 2009
CLICK HERE TO COPY
Actionscript:
  1. import com.actionsnippet.qbox.*;
  2. import Box2D.Common.Math.*;
  3. import Box2D.Dynamics.Joints.*;
  4. [SWF (backgroundColor=0x000000, width=700, height=600, frameRate=60)]
  5. var sim:QuickBox2D = new QuickBox2D(this, {debug:false,gravityY:10, renderJoints:false});
  6. sim.setDefault({fillColor:0xCC0000,lineAlpha:0});
  7. sim.createStageWalls();
  8.  
  9. for (var i:int = 0; i<20; i++){
  10.     sim.addCircle({x:1+i * 0.8, y:1, radius:0.1+Math.random()*0.1, restitution:0.3});
  11. }
  12.  
  13. sim.setDefault({fillColor:0xEFEFEF, fillAlpha:0.5, lineColor:0xFFFFFF, groupIndex:-2});
  14. var ancA:QuickObject = sim.addCircle({x:20, y:12, radius:0.5, density:0, skin:"none"});
  15. var ancB:QuickObject = sim.addCircle({x:20, y:2, radius:0.5, density:0, skin:"none"});
  16. var head:QuickObject = sim.addCircle({x:0, y:-0.6, radius:0.5});
  17. var neck:QuickObject = sim.addBox({x:0, y:1, width:0.5, height:2});
  18. var spindle:QuickObject = sim.addBox({x:0, y:3, width:0.1, height:2})
  19. spindle.userData.visible = false;
  20. var top:QuickObject = sim.addGroup({objects:[head, neck, spindle], x:10, y:5, fixedRotation:true});
  21. var upperLegA:QuickObject = sim.addBox({x:10, y:7.5, width:0.25, height:1.5});
  22. var lowerLegA:QuickObject = sim.addBox({x:10, y:9, width:0.25, height:1.5});
  23. var wheel:QuickObject = sim.addCircle({x:10, y:9, radius:1});
  24. var upperLegB:QuickObject = sim.addBox({x:10, y:7.5, width:0.25, height:1.5});
  25. var lowerLegB:QuickObject = sim.addBox({x:10, y:9, width:0.25, height:1.5});
  26. var upperArmA:QuickObject = sim.addBox({x:10.7, y:5.25, width:1.5, height:0.25});
  27. var lowerArmA:QuickObject = sim.addBox({x:11.8, y:5.25, width:1.2, height:0.25});
  28. var upperArmB:QuickObject = sim.addBox({x:9.5, y:5.25, width:1.5, height:0.25});
  29. var lowerArmB:QuickObject = sim.addBox({x:8.4, y:5.25, width:1.2, height:0.25});
  30. var anchor:b2Vec2 = new b2Vec2();
  31. function connect(a:QuickObject, b:QuickObject, lower:Number, upper:Number, offX:Number=0, offY:Number = 0):QuickObject{
  32.      var min:Number = Math.min(a.y, b.y);
  33.      var max:Number = Math.max(a.y, b.y);
  34.      anchor.y = min + (max - min) * 0.5 + offY;
  35.      min = Math.min(a.x, b.x);
  36.      max = Math.max(a.x, b.x);
  37.      anchor.x = min + (max - min) * 0.5 + offX;
  38.      return sim.addJoint({type:"revolute", a:a.body, b:b.body, x1:anchor.x, y1:anchor.y, lowerAngle:lower, upperAngle:upper});
  39. }
  40. sim.addJoint({type:"revolute", a:wheel.body, b:top.body, x1:wheel.x, y1:wheel.y});
  41. sim.addJoint({type:"revolute", a:lowerLegA.body, b:wheel.body, x1:lowerLegA.x, y1:lowerLegA.y + 0.7});
  42. sim.setDefault({enableLimit:true});
  43. connect(top, upperArmA, 0, 3, -.3, .1);
  44. connect(upperArmA, lowerArmA, -2.5, -1, 0, 0);
  45. connect(top, upperArmB, -3, 0, .3, .1);
  46. connect(upperArmB, lowerArmB, -2.5, -1, 0, 0);
  47. sim.addJoint({type:"distance", a:lowerArmA.body, b:ancA.body, frequencyHz:0.3});
  48. sim.addJoint({type:"distance", a:lowerArmB.body, b:ancB.body, frequencyHz:0.3});
  49. sim.setDefault({enableLimit:true});
  50. connect(top, upperLegA, -6.28, 6, 0, 0.8);
  51. connect(upperLegA, lowerLegA, .1, 6);
  52. wheel.angle = Math.PI;
  53. connect(top, upperLegB, -6.28, 6, 0, 0.8);
  54. connect(upperLegB, lowerLegB, .1, 6);
  55. sim.setDefault({enableLimit:false, type:"revolute"});
  56. sim.addJoint({a:lowerLegB.body, b:wheel.body, x1:lowerLegB.x, y1:lowerLegB.y + 0.7});
  57.  
  58. sim.start();
  59. sim.mouseDrag();
  60.  
  61. var sd:Number = 5, s:Number = 0, t:Number = 0;
  62. addEventListener(Event.ENTER_FRAME, function():void{
  63.     top.angle = Math.cos(t += 0.05) * 0.2;
  64.     if (top.x> 19) sd = -5
  65.     if (top.x <5) sd = 5;
  66.     s += (sd - s) / 8;
  67.     wheel.body.SetAngularVelocity(s);
  68. });

This chunk of code uses QuickBox2D to create a simple looking character riding a unicycle...

Have a look at the swf...

Posted in Box2D, QuickBox2D, motion | Also tagged , , , | 9 Comments

QuickBox2D Floating Walker

By Zevan | August 16, 2009
CLICK HERE TO COPY
Actionscript:
  1. import com.actionsnippet.qbox.*;
  2. import Box2D.Common.Math.*;
  3. import Box2D.Dynamics.Joints.*;
  4.  
  5. [SWF (backgroundColor=0x000000, width=700, height=600, frameRate=60)]
  6.  
  7. var sim:QuickBox2D = new QuickBox2D(this, {gravityY:.2});
  8.  
  9. sim.setDefault({fillColor:0xEFEFEF, fillAlpha:0.5, lineColor:0xFFFFFF});
  10.  
  11. sim.createStageWalls();
  12.  
  13. for (var i:int = 0; i<20; i++){
  14.     sim.addCircle({x:1+i, y:1, radius:0.2, restitution:1});
  15. }
  16.  
  17. var head:QuickObject = sim.addCircle({x:0, y:0, radius:0.5});
  18. var neck:QuickObject = sim.addBox({x:0, y:1, width:0.5, height:2});
  19. var top:QuickObject = sim.addGroup({objects:[head, neck], x:10, y:5, fixedRotation:true});
  20.  
  21. var upperLegA:QuickObject = sim.addBox({x:10, y:7.5, width:0.25, height:1.5,groupIndex:-2});
  22. var lowerLegA:QuickObject = sim.addBox({x:10, y:9, width:0.25, height:1.5,groupIndex:-2});
  23.  
  24. var upperLegB:QuickObject = sim.addBox({x:10, y:7.5, width:0.25, height:1.5,groupIndex:-2});
  25. var lowerLegB:QuickObject = sim.addBox({x:10, y:9, width:0.25, height:1.5,groupIndex:-2});
  26.  
  27. var anchor:b2Vec2 = new b2Vec2();
  28. function connect(a:QuickObject, b:QuickObject, lower:Number, upper:Number, offX:Number=0, offY:Number = 0):QuickObject{
  29.      var min:Number = Math.min(a.y, b.y);
  30.      var max:Number = Math.max(a.y, b.y);
  31.      anchor.y = min + (max - min) * 0.5 + offY;
  32.      min = Math.min(a.x, b.x);
  33.      max = Math.max(a.x, b.x);
  34.      anchor.x = min + (max - min) * 0.5 + offX;
  35.      return sim.addJoint({a:a.body, b:b.body, x1:anchor.x, y1:anchor.y, lowerAngle:lower, upperAngle:upper});
  36. }
  37.  
  38. sim.setDefault({type:"revolute", collideConnected:false, enableLimit:true, enableMotor:true, maxMotorTorque:250, lineColor:0xFFFFFF});
  39.  
  40. var upperLegAJoint:QuickObject = connect(top, upperLegA, -1, 1, 0, 0.8);
  41. var upperLegBJoint:QuickObject = connect(top, upperLegB, -1, 1, 0, 0.8);
  42.  
  43. var lowerLegAJoint:QuickObject = connect(upperLegA, lowerLegA, -1, 1);
  44. var lowerLegBJoint:QuickObject = connect(upperLegB, lowerLegB, -1, 1);
  45.  
  46. sim.start();
  47. sim.mouseDrag();
  48.  
  49.  
  50. var j:b2RevoluteJoint;
  51. var t:Number = -Math.PI * 0.5;
  52. addEventListener(Event.ENTER_FRAME, onLoop);
  53. function onLoop(evt:Event):void {
  54.    
  55.     var s1:Number = 1*Math.sin(t);
  56.     var s2:Number = 1*Math.sin(t+Math.PI);
  57.     t+= 0.05;
  58.    
  59.     top.body.SetAngularVelocity(s1 * 0.25);
  60.    
  61.     j =  upperLegAJoint.joint as b2RevoluteJoint;
  62.     j.SetMotorSpeed(s1);
  63.    
  64.     j =  upperLegBJoint.joint as b2RevoluteJoint;
  65.     j.SetMotorSpeed(s2);
  66.      
  67.     j = lowerLegAJoint.joint as b2RevoluteJoint;
  68.     j.SetMotorSpeed(-s2);
  69.    
  70.     j = lowerLegBJoint.joint as b2RevoluteJoint;
  71.     j.SetMotorSpeed(-s1);
  72. }

Experimenting with primitive robot designs... this was just an improvised design - it looks like it may make sense to break out a pencil and some paper - or my wacom... to get something interesting...


Have a look at the swf...


Posted in Box2D, QuickBox2D, motion | Also tagged , , , | 1 Comment

QuickBox2D Prismatic Joint

By Zevan | August 15, 2009
CLICK HERE TO COPY
Actionscript:
  1. import com.actionsnippet.qbox.*;
  2. import Box2D.Common.Math.*;
  3.  
  4. [SWF (backgroundColor=0x000000, width=700, height=600, frameRate=60)]
  5.  
  6. var sim:QuickBox2D = new QuickBox2D(this);
  7.  
  8. sim.setDefault({fillColor:0xCCCCCC, lineColor:0x3355AA});
  9.  
  10. sim.createStageWalls();
  11.  
  12. var box:QuickObject = sim.addBox({x:10, y:10, density:0});
  13. var circle:QuickObject = sim.addCircle({x:10, y:13});
  14.  
  15. sim.addJoint({type:"prismatic", a:box.body, b:circle.body, axis:new b2Vec2(1, 0), upperTranslation:3, lowerTranslation:-3, enableLimit:true, motorSpeed:10, maxMotorForce:10, enableMotor:true});
  16.  
  17. sim.start();
  18. sim.mouseDrag();

Simple prismatic joint demo. Prismatic joints are odd, it took me awhile to realize how to use them and what they can be used for... Plan on using them in the creation of some Box2D machines in the near futrure...

Check out the swf

Posted in Box2D, QuickBox2D, motion | Also tagged , , , | 1 Comment