changed Math.random to Common.random and use a seeded RNG

liabru · May 10, 2014 · 0a46cb2 · 0a46cb2
1 parent 3043baa
commit 0a46cb2
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Showing 3 changed files with 32 additions and 18 deletions.
diff --git a/demo/js/Demo.js b/demo/js/Demo.js
@@ -96,15 +96,15 @@
 
             // round the edges of some bodies
             var chamfer = null;
-            if (sides > 2 && Math.random() > 0.7) {
+            if (sides > 2 && Common.random() > 0.7) {
                 chamfer = {
                     radius: 10
                 };
             }
 
             switch (Math.round(Common.random(0, 1))) {
             case 0:
-                if (Math.random() < 0.8) {
+                if (Common.random() < 0.8) {
                     return Bodies.rectangle(x, y, Common.random(25, 50), Common.random(25, 50), { chamfer: chamfer });
                 } else {
                     return Bodies.rectangle(x, y, Common.random(80, 120), Common.random(25, 30), { chamfer: chamfer });
@@ -243,7 +243,7 @@
             switch (Math.round(Common.random(0, 1))) {
 
             case 0:
-                if (Math.random() < 0.8) {
+                if (Common.random() < 0.8) {
                     return Bodies.rectangle(x, y, Common.random(20, 50), Common.random(20, 50));
                 } else {
                     return Bodies.rectangle(x, y, Common.random(80, 120), Common.random(20, 30));
@@ -365,7 +365,7 @@
             switch (Math.round(Common.random(0, 1))) {
 
             case 0:
-                if (Math.random() < 0.8) {
+                if (Common.random() < 0.8) {
                     return Bodies.rectangle(x, y, Common.random(20, 50), Common.random(20, 50));
                 } else {
                     return Bodies.rectangle(x, y, Common.random(80, 120), Common.random(20, 30));
@@ -523,7 +523,7 @@
             switch (Math.round(Common.random(0, 1))) {
 
             case 0:
-                if (Math.random() < 0.8) {
+                if (Common.random() < 0.8) {
                     return Bodies.rectangle(x, y, Common.random(20, 50), Common.random(20, 50));
                 } else {
                     return Bodies.rectangle(x, y, Common.random(80, 120), Common.random(20, 30));
@@ -551,7 +551,7 @@
             switch (Math.round(Common.random(0, 1))) {
 
             case 0:
-                if (Math.random() < 0.8) {
+                if (Common.random() < 0.8) {
                     return Bodies.rectangle(x, y, Common.random(20, 50), Common.random(20, 50));
                 } else {
                     return Bodies.rectangle(x, y, Common.random(80, 120), Common.random(20, 30));
@@ -580,7 +580,7 @@
             switch (Math.round(Common.random(0, 1))) {
 
             case 0:
-                if (Math.random() < 0.8) {
+                if (Common.random() < 0.8) {
                     return Bodies.rectangle(x, y, Common.random(20, 50), Common.random(20, 50));
                 } else {
                     return Bodies.rectangle(x, y, Common.random(80, 120), Common.random(20, 30));
@@ -647,8 +647,8 @@
                     var forceMagnitude = 0.04 * body.mass;
 
                     Body.applyForce(body, { x: 0, y: 0 }, { 
-                        x: (forceMagnitude + Math.random() * forceMagnitude) * Common.choose([1, -1]), 
-                        y: -forceMagnitude + Math.random() * -forceMagnitude
+                        x: (forceMagnitude + Common.random() * forceMagnitude) * Common.choose([1, -1]), 
+                        y: -forceMagnitude + Common.random() * -forceMagnitude
                     });
                 }
             }
@@ -699,7 +699,7 @@
             switch (Math.round(Common.random(0, 1))) {
 
             case 0:
-                if (Math.random() < 0.8) {
+                if (Common.random() < 0.8) {
                     return Bodies.rectangle(x, y, Common.random(20, 50), Common.random(20, 50), bodyOptions);
                 } else {
                     return Bodies.rectangle(x, y, Common.random(80, 120), Common.random(20, 30), bodyOptions);
@@ -955,8 +955,8 @@
                     var forceMagnitude = 0.01 * body.mass;
 
                     Body.applyForce(body, { x: 0, y: 0 }, { 
-                        x: (forceMagnitude + Math.random() * forceMagnitude) * Common.choose([1, -1]), 
-                        y: -forceMagnitude + Math.random() * -forceMagnitude
+                        x: (forceMagnitude + Common.random() * forceMagnitude) * Common.choose([1, -1]), 
+                        y: -forceMagnitude + Common.random() * -forceMagnitude
                     });
                 }
             }
@@ -1069,7 +1069,7 @@
         ]);
 
         var stack = Composites.stack(20, 20, 15, 4, 0, 0, function(x, y, column, row) {
-            if (Math.random() > 0.35) {
+            if (Common.random() > 0.35) {
                 return Bodies.rectangle(x, y, 64, 64, {
                     render: {
                         strokeStyle: '#ffffff',
@@ -1110,7 +1110,7 @@
             switch (Math.round(Common.random(0, 1))) {
 
             case 0:
-                if (Math.random() < 0.8) {
+                if (Common.random() < 0.8) {
                     return Bodies.rectangle(x, y, Common.random(20, 50), Common.random(20, 50));
                 } else {
                     return Bodies.rectangle(x, y, Common.random(80, 120), Common.random(20, 30));
@@ -1275,6 +1275,9 @@
         // reset id pool
         Common._nextId = 0;
 
+        // reset random seed
+        Common._seed = 0;
+
         // reset mouse offset and scale (only required for Demo.views)
         Mouse.setScale(_engine.input.mouse, { x: 1, y: 1 });
         Mouse.setOffset(_engine.input.mouse, { x: 0, y: 0 });

diff --git a/demo/js/DemoMobile.js b/demo/js/DemoMobile.js
@@ -66,7 +66,7 @@
             switch (Math.round(Common.random(0, 1))) {
 
             case 0:
-                if (Math.random() < 0.8) {
+                if (Common.random() < 0.8) {
                     return Bodies.rectangle(x, y, Common.random(20, 40), Common.random(20, 40), { friction: 0.01, restitution: 0.4 });
                 } else {
                     return Bodies.rectangle(x, y, Common.random(80, 120), Common.random(20, 30), { friction: 0.01, restitution: 0.4 });
@@ -139,6 +139,8 @@
 
     Demo.reset = function() {
         var _world = _engine.world;
+
+        Common._seed = 2;
 
         World.clear(_world);
         Engine.clear(_engine);

diff --git a/src/core/Common.js b/src/core/Common.js
@@ -9,6 +9,7 @@ var Common = {};
 (function() {
 
     Common._nextId = 0;
+    Common._seed = 0;
 
     /**
      * Description
@@ -132,7 +133,7 @@ var Common = {};
      */
     Common.shuffle = function(array) {
         for (var i = array.length - 1; i > 0; i--) {
-            var j = Math.floor(Math.random() * (i + 1));
+            var j = Math.floor(Common.random() * (i + 1));
             var temp = array[i];
             array[i] = array[j];
             array[j] = temp;
@@ -147,7 +148,7 @@ var Common = {};
      * @return {object} A random choice object from the array
      */
     Common.choose = function(choices) {
-        return choices[Math.floor(Math.random() * choices.length)];
+        return choices[Math.floor(Common.random() * choices.length)];
     };
 
     /**
@@ -222,7 +223,9 @@ var Common = {};
      * @return {number} A random number between min and max inclusive
      */
     Common.random = function(min, max) {
-        return min + Math.random() * (max - min);
+        min = (typeof min !== "undefined") ? min : 0;
+        max = (typeof max !== "undefined") ? max : 1;
+        return min + _seededRandom() * (max - min);
     };
 
     /**
@@ -278,4 +281,10 @@ var Common = {};
         return Common._nextId++;
     };
 
+    var _seededRandom = function() {
+        // https://gist.github.com/ngryman/3830489
+        Common._seed = (Common._seed * 9301 + 49297) % 233280;
+        return Common._seed / 233280;
+    };
+
 })();