Actionscript:
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[SWF(width=401,height=401,background=0xEFEFEF)]
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var w:Number = stage.stageWidth-1;
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var h:Number = stage.stageHeight-1;
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var tileSize:Number = 20;
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var halfTileSize:Number = 20;
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var hTiles:Number = w / tileSize;
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var vTiles:Number = h / tileSize;
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var world:Shape = Shape(addChild(new Shape()));
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var map:Array=[];
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populateMap();
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var gridColor:uint = 0xCCCCCC;
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grid(tileSize, gridColor);
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vTiles -= 1;
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var movers:Array = [];
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for (var i:int = 0; i<100; i++){
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movers.push(makeMover(i % hTiles, int( i / hTiles),0x000000))
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movers.push(makeMover(i % hTiles, vTiles - int( i / hTiles),0xFF0000))
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}
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var moverNum:int = movers.length;
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hTiles -= 1;
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addEventListener(Event.ENTER_FRAME, onLoop);
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function onLoop(evt:Event):void {
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world.graphics.clear();
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for (var i:int = 0; i<moverNum; i++){
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movers[i]();
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}
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}
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function populateMap():void{
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for (var i:int = 0; i<vTiles; i++){
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map[i] = [];
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for (var j:int = 0; j<hTiles; j++){
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map[i][j] = 0;
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}
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}
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}
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function grid(size:Number=30, lineColor:uint=0xFFFF00, lineAlpha:Number=1):void {
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with(graphics){
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lineStyle(0, lineColor, lineAlpha);
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drawRect(0,0,w,h);
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for (var i:Number = size; i<w; i+=size) {
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moveTo(i, 0);
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lineTo(i, w);
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}
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for (i = size; i<h; i+=size) {
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moveTo(0, i);
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lineTo(h, i);
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}
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}
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}
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function makeMover(x:Number, y:Number, col:uint):Function{
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var xp:Number = x;
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var yp:Number = y;
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var prevX:Number = x;
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var prevY:Number = y;
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map[yp][xp] = 1;
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var dx:Number = xp;
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var dy:Number = yp;
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var counter:int = 0;
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return function():void{
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if (counter> 20){
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if (int(Math.random()*30) == 1){
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xp += int(Math.random()*2) - 1 | 1;
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xp = xp <0 ? 0 : xp;
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xp = xp> hTiles ? hTiles : xp;
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if (map[yp][xp] == 1){
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xp = prevX;
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}else{
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map[prevY][prevX] = 0;
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map[yp][xp] = 1;
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counter = 0;
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}
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prevX = xp;
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}else
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if (int(Math.random()*30) == 1){
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yp += int(Math.random()*2) - 1 | 1;
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yp = yp <0 ? 0 : yp;
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yp = yp> vTiles ? vTiles : yp;
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if (map[yp][xp] == 1){
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yp = prevY;
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}else{
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map[prevY][prevX] = 0;
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map[yp][xp] = 1;
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counter = 0;
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}
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prevY = yp;
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}
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}
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counter++;
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dx += (xp - dx) * 0.5;
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dy += (yp - dy) * 0.5;
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with(world.graphics){
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lineStyle(0, gridColor,1, true)
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beginFill(col);
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drawRect(dx * tileSize, dy * tileSize, tileSize, tileSize);
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}
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}
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}
This (somewhat long) snippet moves boxes around on a grid - the boxes avoid one another by reading values in a 2D array. This technique can also be used for collision detection in tile-based games.
Have a look at the swf here...
Actionscript:
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[SWF(width=800, height=600)]
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var xn1:Number;
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var xn:Number = Math.random() * Math.random() * .2;
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var inc:int = 0;
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var xp:Number = 10;
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var yp:Number = 10;
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var count:int = 1;
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scaleX = scaleY = 2;
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graphics.lineStyle(0,0x00000);
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addEventListener(Event.ENTER_FRAME, onLoop);
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function onLoop(evt:Event):void {
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-
xn1 = 2 * xn % 1;
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xn = xn1;
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if (inc == 0){
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graphics.moveTo(xp + inc, yp + 30 - xn1 * 30);
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}else{
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graphics.lineTo(xp + inc, yp + 30 - xn1 * 30);
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}
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inc++
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if (inc == 50){
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inc = 0;
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xp = 10 + count % 6 * 60;
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yp = 10 + int(count / 6) * 60;
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xn = Math.random() * Math.random() * .2;
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trace(xn);
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count++;
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}
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}
This snippet plots 2x mod 1 maps with random starting values for xn. More info over at wikipedia and mathworld.
Actionscript:
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var rand:Number = Math.random() * Math.random() * Math.random();
This is a trick I use when I need more contrast in my random numbers. In this case, the variable rand will get closer to the number 1 significantly less frequently than if you just used Math.random() once.
To illustrate this I created this snippet:
Actionscript:
-
[SWF(width=800, height=600)]
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var r:Number = Math.random() * Math.random() * Math.random();
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var inc:int = 0;
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var xp:Number = 10;
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var yp:Number = 10;
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var count:int = 1;
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-
var compare:Shape = Shape(addChild(new Shape()));
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compare.graphics.lineStyle(0,0x2222FF);
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graphics.lineStyle(0,0x00000);
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scaleX = scaleY = 2;
-
-
addEventListener(Event.ENTER_FRAME, onLoop);
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function onLoop(evt:Event):void {
-
-
r = Math.random() * Math.random() * Math.random();
-
-
if (inc == 0){
-
graphics.moveTo(xp + inc, yp + 30 - r * 30);
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}else{
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graphics.lineTo(xp + inc, yp + 30 - r * 30);
-
}
-
-
r = Math.random();
-
if (inc == 0){
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compare.graphics.moveTo(xp + inc, yp + 70 - r * 30);
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}else{
-
compare.graphics.lineTo(xp + inc, yp + 70 - r * 30);
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}
-
inc++;
-
if (inc == 50){
-
inc = 0;
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xp = 10 + count % 6 * 60;
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yp = 10 + int(count / 6) * 80;
-
r = Math.random()*Math.random();
-
count++;
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}
-
}
The blue lines plots normal Math.random() and the black lines plots Math.random()*Math.random()*Math.random()
Actionscript:
-
import com.actionsnippet.qbox.*;
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-
var sim:QuickBox2D = new QuickBox2D(this);
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-
sim.createStageWalls({lineAlpha:0,fillColor:0x000000})
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sim.addBox({x:3, y:3, width:3, height:3, skin:BoxSkin});
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sim.addCircle({x:3, y:8,radius:1.5, skin:CircleSkin});
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sim.addPoly({x:6, y:3, verts:[[1.5,0,3,3,0,3,1.5,0]], skin:TriangleSkin});
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-
sim.addBox({x:6, y:3, width:3, height:3, skin:BoxSkin});
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sim.addCircle({x:6, y:8,radius:1.5, skin:CircleSkin});
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sim.addPoly({x:12, y:3, verts:[[1.5,0,3,3,0,3,1.5,0]], skin:TriangleSkin});
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-
sim.start();
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sim.mouseDrag();
You'll need this fla to run this snippet since the graphics are in the library. This snippet shows how to easily use linkage classes as the graphics for your rigid bodies. This was actually one of the first features I implemented in QuickBox2D.
Take a look at the swf here...
