Tag Archives: as3

QuickBox2D Mini-Poly Editor

By Zevan | December 1, 2009
CLICK HERE TO COPY
Actionscript:
  1. [SWF(width = 800, height = 600, frameRate = 60)]
  2. import com.actionsnippet.qbox.*;
  3. stage.frameRate = 60;
  4.  
  5. var sim:QuickBox2D = new QuickBox2D(this);
  6.  
  7. sim.createStageWalls();
  8.  
  9. sim.start();
  10.  
  11. var output:TextField = new TextField();
  12. output.text = "Click anywhere to add points to a polygon. Hit any key to test.\n\n";
  13. output.x = output.y = 50;
  14. with(output) width = 300, height = 400, border = true, selectable = true, wordWrap = true, multiline = true;
  15. addChild(output);
  16.  
  17. function display(str:*):void{
  18.     output.appendText(str.toString() + "\n");
  19. }
  20.                                
  21. var points:Array = [];
  22. var poly:Shape = new Shape();
  23. addChild(poly);
  24.  
  25. stage.addEventListener(MouseEvent.CLICK, onClick);
  26. stage.addEventListener(KeyboardEvent.KEY_DOWN, onKeyPressed);
  27.  
  28. function onClick(evt:MouseEvent):void {
  29.     if (points.length == 0){
  30.         poly.graphics.beginFill(0xCCCCCC);
  31.         poly.graphics.lineStyle(1, 0xFF0000);
  32.         poly.graphics.moveTo(mouseX, mouseY);
  33.     }else{
  34.         poly.graphics.lineTo(mouseX, mouseY);
  35.     }
  36.     poly.graphics.drawCircle(mouseX, mouseY, 2);
  37.      
  38.     points.push(mouseX / 30.0, mouseY / 30.0);
  39. }
  40.  
  41. function onKeyPressed(evt:KeyboardEvent):void {
  42.      // average all points
  43.      var avgX:Number=0
  44.      var avgY:Number = 0;
  45.      
  46.      for (var i:int = 0; i<points.length; i+=2){
  47.          avgX += points[i];
  48.          avgY += points[i + 1];
  49.      }
  50.    
  51.      avgX /= points.length/2;
  52.      avgY /=  points.length/2;
  53.      avgX = avgX;
  54.      avgY = avgY;
  55.      
  56.      // subtract averages and fix decimal place
  57.       for (i = 0; i<points.length; i+=2){
  58.           var yp:int = i + 1;
  59.           points[i] -= avgX;
  60.           points[yp] -= avgY;
  61.           points[i] = Number(points[i].toFixed(2));
  62.           points[yp] = Number(points[yp].toFixed(2));
  63.      }
  64.      
  65.      display("points array:");
  66.      display(points);
  67.      
  68.      try{
  69.          var p:QuickObject = sim.addPoly({x:avgX, y:avgY, points:points});
  70.          p.userData.graphics.beginFill(0xFF0000);
  71.          p.userData.graphics.drawCircle(0,0,5);
  72.      }catch(e:*){
  73.         display("Invalid polygon data!");
  74.      }
  75.      
  76.      poly.graphics.clear();
  77.      points = [];
  78. }

This snippet shows the basic concepts needed to go about creating a polygon editor for QuickBox2D. I have an unreleased editor that I use for my QuickBox2D projects, at some point I may release it... but for now I figured I'd post this extremely simplified version for people to expand on.


Have a look at the swf here...

Posted in Box2D, QuickBox2D | Also tagged , , , | 26 Comments

Float as a Fraction

By Zevan | November 29, 2009
CLICK HERE TO COPY
Actionscript:
  1. // print some floats as fractions
  2. printFraction(0.5);
  3. printFraction(0.75);
  4. printFraction(0.48);
  5.  
  6. // try something a little more complex
  7. var float:Number = 0.98765432;
  8. trace("\na more complex example:");
  9. printFraction(float);
  10. var frac:Array = asFraction(float);
  11. trace("double check it:");
  12. trace(frac[0] + "/" + frac[1] +" = " + frac[0] / frac[1]);
  13.  
  14. /* outputs:
  15. 0.5 = 1/2
  16. 0.75 = 3/4
  17. 0.48 = 12/25
  18.  
  19. a more complex example:
  20. 0.98765432 = 12345679/12500000
  21. double check it:
  22. 12345679/12500000 = 0.98765432
  23. */
  24.  
  25.  
  26. function printFraction(n:Number):void{
  27.     var frac:Array = asFraction(n);
  28.     trace(n + " = " + frac[0] + "/" + frac[1]);
  29. }
  30.  
  31. // takes any value less than one and returns an array
  32. // with the numerator at index 0 and the denominator at index 1
  33. function asFraction(num:Number):Array{
  34.     var decimalPlaces:int = num.toString().split(".")[1].length;
  35.     var denom:Number = Math.pow(10, decimalPlaces);
  36.     return reduceFraction(num * denom, denom);
  37. }
  38.  
  39. // divide the numerator and denominator by the GCF
  40. function reduceFraction(numerator:int, denominator:Number):Array{
  41.     // divide by the greatest common factor
  42.     var divisor:int = gcf(numerator, denominator);
  43.     if (divisor){
  44.         numerator /= divisor;
  45.         denominator /= divisor;
  46.     }
  47.     return [numerator, denominator];
  48. }
  49.                    
  50. // get the greatest common factor of two integers
  51. function gcf(a:int, b:int):int{
  52.     var remainder:int;
  53.     var factor:Number = 0;
  54.     var maxIter:int = 100;
  55.     var i:int = 0;
  56.     while (1){
  57.         if (b> a){
  58.            var swap:int = a;
  59.            a = b;
  60.            b = swap;
  61.         }
  62.         remainder = a % b;
  63.         a = b;
  64.         b = remainder
  65.         if (remainder == 0){
  66.             factor = a;
  67.             break;
  68.         }else if (remainder==1){
  69.             break;
  70.         }else if (i> maxIter){
  71.             trace("failed to calculate gcf");
  72.             break;
  73.         }
  74.         i++;
  75.     }
  76.     return factor;
  77. }

This snippet contains a few functions for calculating fractions based on float values. Writing this brought back some memories from grade school math.

Posted in Math, misc | Also tagged , | 4 Comments

Greatest Common Factor (divisor)

By Zevan | November 28, 2009
CLICK HERE TO COPY
Actionscript:
  1. trace(gcf(75,145));
  2.  
  3. // outputs 5
  4.  
  5. function gcf(a:int, b:int):int{
  6.     var remainder:int;
  7.     var factor:Number = 0;
  8.     while (1){
  9.         if (b> a){
  10.            var swap:int = a;
  11.            a = b;
  12.            b = swap;
  13.         }
  14.         remainder = a % b;
  15.         a = b;
  16.         b = remainder
  17.         if (remainder == 0){
  18.             factor = a;
  19.             break;
  20.         }else if (remainder==1){
  21.          
  22.             break;
  23.         }
  24.     }
  25.     return factor;
  26. }

I was messing around with Egyptian Fractions and found myself in need of some interesting functions. The first function I realized I would be needing was for a greatest common factor (GCF or GCD).

The above snippet is a quick implementation of Euclid's algorithm. It will return 0 if no GCF is found...

I wrote a few helper functions while working with Egyptian fractions... will post them over the next few days.

Posted in Math | Also tagged , | 4 Comments

Ancient Egyptian Multiplication

By Zevan | November 27, 2009
CLICK HERE TO COPY
Actionscript:
  1. egyptianMultiply(12, 99);
  2.  
  3. // trace(12 * 99) // test to make sure it works
  4.  
  5. /* outputs:
  6. /64 768
  7. /32 384
  8.  16 192
  9.  8 96
  10.  4 48
  11. /2 24
  12. /1 12
  13. ---
  14. 1188
  15. */
  16.  
  17.  
  18. function egyptianMultiply(valueA:Number, valueB:Number):void {
  19.    
  20.     var left:Array = [];
  21.     var right:Array = []
  22.    
  23.     // swap if valueB is smaller than value A
  24.     if (valueB <valueA){
  25.         var swap:int = valueB;
  26.         valueB = valueA;
  27.         valueA = swap;
  28.     }
  29.    
  30.     // create left and right columns
  31.     var currentLeft:int = 1;
  32.     var currentRight:int = valueA;
  33.    
  34.     while (currentLeft <valueB){
  35.         left.push(currentLeft);
  36.         right.push(currentRight);
  37.         currentRight += currentRight;
  38.         currentLeft += currentLeft;
  39.     }
  40.    
  41.    
  42.     // add up the right column based on the left
  43.     currentLeft = 0;
  44.     var rightSum:int;
  45.     var leftSum:int;
  46.     var i:int = left.length - 1;
  47.    
  48.     while (currentLeft != valueB){
  49.      
  50.       leftSum = currentLeft + left[i];
  51.       // if the next number causes the sum
  52.       // to go above valueB, skip it
  53.       if (leftSum <= valueB){
  54.         currentLeft = leftSum;
  55.         rightSum += right[i];
  56.         trace("/" + left[i]  + " " + right[i]);
  57.       } else {
  58.         trace(" " + left[i]  + " " + right[i]);
  59.       }
  60.       i--;
  61.     }
  62.     trace("---");
  63.     trace(rightSum);
  64. }

Someone mentioned egyptian multiplication to me yesterday... So read a little about it here and whipped up this example. For some reason I decided to do it in processing ... once it worked I ported it to ActionScript.

The above link describing the technique I used is from http://www.jimloy.com/... I haven't spent much time digging around the site, but it appears to have some pretty nice stuff on it...

If you're curious, here is the original processing version:

CLICK HERE TO COPY
JAVA:
  1. Vector left = new Vector();
  2. Vector right = new Vector();
  3.  
  4. int valueA = 10;
  5. int valueB = 8;
  6.  
  7. if (valueB <valueA){
  8.     int swap = valueB;
  9.     valueB = valueA;
  10.     valueA = swap;
  11. }
  12.  
  13. int currentLeft = 1;
  14. int currentRight = valueA;
  15. while (currentLeft <valueB){
  16.     left.add(currentLeft);
  17.     right.add(currentRight);
  18.     currentRight += currentRight;
  19.     currentLeft += currentLeft;
  20. }
  21.  
  22. currentLeft = 0;
  23.  
  24. int result = 0;
  25. int i = left.size() - 1;
  26. while (currentLeft != valueB){
  27.  
  28.   int temp = currentLeft + (Integer) left.get(i);
  29.   if (temp <= valueB){
  30.    
  31.     currentLeft = temp;
  32.     result += (Integer) right.get(i);
  33.     println("/" + left.get(i) + " " + right.get(i));
  34.   } else {
  35.     println(" " + left.get(i)  + " " + right.get(i));
  36.   }
  37.    
  38.   i--;
  39. }
  40. println("---");
  41. println(result);

After writing, this I took a look at the wikipedia entry... I also found myself on this short page about a scribe called Ahmes. (I recommend reading this if you are interested in PI)

Posted in Math, misc | Also tagged , , | 1 Comment