Solves issue jdan#9 : paths ordering and shapes ordering

js/isomer.js

@@ -82,6 +82,32 @@ Isomer.prototype.add = function (item, baseColor) {
   }
 };
 
+/**
+ * Adds an array of {shape: yourShape, color: yourColor} to the scene,
+ * ordered so that distant faces are displayed first
+ *  */
+Isomer.prototype.addOrdered = function (item) { // array of {shape:, color:}
+  var Point = Isomer.Point;
+  var observer = new Point(-10, -10, 10);
+  var pathList = [];
+  var index = 0;
+
+  for (var i = 0; i < item.length; i++) {
+    for(var j = 0 ; j < item[i].shape.paths.length ; j++){
+      pathList[index] = {
+        path: item[i].shape.paths[j],
+        color: item[i].color
+      };
+      index++;
+    }
+  }
+  pathList.sort(function(pathA, pathB){return (pathA.closerThan(pathB, observer))?1:-1;});
+
+  for (var i = 0 ; i < pathList.length ; i++) {
+    this._addPath(pathList[i].path, pathList[i].color);
+  }
+};
+
 
 /**
  * Adds a path to the scene

js/path.js

@@ -88,6 +88,39 @@
   };
 
 
+  /**
+   * If pathB ("this") is closer from the observer than pathA, it must be drawn after.
+   * It is closer if one of its vertices and the observer are on the same side of the plane defined by pathA.
+   */
+  Path.prototype.closerThan = function(pathA, observer) {
+    var i = 0;
+    // the plane containing pathA is defined by the three points A, B, C
+    var AB = Vector.fromTwoPoints(pathA.points[0], pathA.points[1]);
+    var AC = Vector.fromTwoPoints(pathA.points[0], pathA.points[2]);
+    var n = Vector.crossProduct(AB, AC);
+
+    var OA = Vector.fromTwoPoints(Point.ORIGIN, pathA.points[0]);
+    var OU = Vector.fromTwoPoints(Point.ORIGIN, observer); //U = user = observer
+
+    // Plane defined by pathA such as ax + by + zc = d
+    // Here d = nx*x + ny*y + nz*z = n.OA
+    var d = Vector.dotProduct(n, OA);
+
+    var observerPosition = Vector.dotProduct(n, OU) - d;
+
+    for (i = 0; i < this.points.length; i++) {
+      var OP = Vector.fromTwoPoints(Point.ORIGIN, this.points[i]);
+      var pPosition = Vector.dotProduct(n, OP) - d;
+      if(observerPosition * pPosition > 0){ //same sign = same side
+        return 1;
+      }
+    }
+
+    return 0; 
+
+  };
+
+
   /**
    * Some paths to play with
    */