diff --git a/js/isomer.js b/js/isomer.js
index 155835f..5bd9bc7 100644
--- a/js/isomer.js
+++ b/js/isomer.js
@@ -36,6 +36,11 @@ function Isomer(canvasId, options) {
    */
   this.colorDifference = 0.20;
   this.lightColor = options.lightColor || new Color(255, 255, 255);
+
+  /**
+   * List of {path, color, shapeName} to draw
+   */
+  this.scene = [];
 }
 
 /**
@@ -67,25 +72,215 @@ Isomer.prototype._translatePoint = function (point) {
 /**
  * Adds a shape or path to the scene
  *
- * This method also accepts arrays
+ * This method also accepts arrays.
+ * By default or if expertMode=0, shapes are drawn
  */
-Isomer.prototype.add = function (item, baseColor) {
+Isomer.prototype.add = function (item, baseColor, expertMode, name) {
+  var expertModeValid = !!expertMode;
   if (Object.prototype.toString.call(item) == '[object Array]') {
     for (var i = 0; i < item.length; i++) {
-      this.add(item[i], baseColor);
+      this.add(item[i], baseColor, expertModeValid, name);
     }
   } else if (item instanceof Path) {
-    this._addPath(item, baseColor);
+    if(expertModeValid){
+      this.scene[this.scene.length] = {path:item, color:baseColor, shapeName:(name||'')};
+    } else {
+      this._addPath(item, baseColor);
+    }
   } else if (item instanceof Shape) {
-    /* Fetch paths ordered by distance to prevent overlaps */
     var paths = item.orderedPaths();
     for (var i in paths) {
-      this._addPath(paths[i], baseColor);
+      if(expertModeValid){
+        this.scene[this.scene.length] = {path:paths[i], color:baseColor, shapeName:(name||'')};
+      } else {
+        this._addPath(paths[i], baseColor);
+      }
+    }
+  }
+};
+
+/**
+ * Draws the content of this.scene
+ * By default, does not sort the paths between shapes
+ */
+Isomer.prototype.draw = function(sortPath){
+  var sortValid = !!sortPath;
+  if(sortValid){
+    this.sortPaths();
+  }
+  for (var i in this.scene){
+    this._addPath(this.scene[i].path, this.scene[i].color);
+  }
+}
+
+
+/**
+ * Sorts the paths contained in this.scene,
+ * ordered so that distant faces are displayed first
+ *  */
+Isomer.prototype.sortPaths = function () {
+  var Point = Isomer.Point;
+  var observer = new Point(-10, -10, 20);
+  var pathList = [];
+  for (var i = 0; i < this.scene.length; i++) {
+    var currentPath = this.scene[i];
+    pathList[i] = {
+      path: currentPath.path,
+      polygon: currentPath.path.points.map(this._translatePoint.bind(this)),
+      color: currentPath.color,
+      drawn: 0,
+      shapeName: currentPath.shapeName
+
+    };
+  }
+  this.scene.length = 0;
+
+ // topological sort
+  
+  var drawBefore = [];
+  for (var i = 0 ; i < pathList.length ; i++){
+    drawBefore[i] = [];
+  }
+  for (var i = 0 ; i < pathList.length ; i++){
+    for (var j = 0 ; j < i ; j++){
+      if(this._hasIntersection(pathList[i].polygon, pathList[j].polygon)){
+        var cmpPath = pathList[i].path.closerThan(pathList[j].path, observer);
+        if(cmpPath < 0){
+          drawBefore[i][drawBefore[i].length] = j;
+        }
+        if(cmpPath > 0){
+          drawBefore[j][drawBefore[j].length] = i;
+        }
+      }
+    }
+  }
+  var drawThisTurn = 1;
+  var index = 0;
+  while(drawThisTurn == 1){
+    index++;
+    drawThisTurn = 0;
+    for (var i = 0 ; i < pathList.length ; i++){
+      if(pathList[i].drawn == 0){
+        var canDraw = 1;
+        for (var j = 0 ; j < drawBefore[i].length ; j++){
+          if(pathList[drawBefore[i][j]].drawn == 0){canDraw = 0;}
+        }
+        if(canDraw == 1){
+          this.add(pathList[i].path, pathList[i].color, true, pathList[i].shapeName);
+          drawThisTurn = 1;
+          pathList[i].drawn = 1;
+        }
+      }
+    }
+  }
+  //purge 
+  //could be done more in a smarter order, that's why drawn is an element of pathList[] and not a separate array
+  for (var i = 0 ; i < pathList.length ; i++){
+    if(pathList[i].drawn == 0){
+      this.add(pathList[i].path, pathList[i].color, true, pathList[i].shapeName);
     }
   }
 };
 
 
+//+ Jonas Raoni Soares Silva
+//@ http://jsfromhell.com/math/is-point-in-poly [rev. #0]
+//see also http://jsperf.com/ispointinpath-boundary-test-speed/2
+function isPointInPoly(poly, pt){
+  for(var c = false, i = -1, l = poly.length, j = l - 1; ++i < l; j = i)
+    ((poly[i].y <= pt.y && pt.y < poly[j].y) || (poly[j].y <= pt.y && pt.y < poly[i].y))
+    && (pt.x < (poly[j].x - poly[i].x) * (pt.y - poly[i].y) / (poly[j].y - poly[i].y) + poly[i].x)
+    && (c = !c);
+  return c;
+}
+
+
+/**
+ * Does polygonA has intersection with polygonB ?
+ * Naive approach done first : approximate the polygons with a rectangle
+ * Then more complex method : see if edges cross, or one contained in the other
+ */
+Isomer.prototype._hasIntersection = function(pointsA, pointsB) {
+  var i, j;
+  var AminX = pointsA[0].x;
+  var AminY = pointsA[0].y;
+  var AmaxX = AminX;
+  var AmaxY = AminY;
+  var BminX = pointsB[0].x;
+  var BminY = pointsB[0].y;
+  var BmaxX = BminX;
+  var BmaxY = BminY;
+  for(i = 0 ; i < pointsA.length ; i++){
+    AminX = Math.min(AminX, pointsA[i].x);
+    AminY = Math.min(AminY, pointsA[i].y);
+    AmaxX = Math.max(AmaxX, pointsA[i].x);
+    AmaxY = Math.max(AmaxY, pointsA[i].y);
+  }
+  for(i = 0 ; i < pointsB.length ; i++){
+    BminX = Math.min(BminX, pointsB[i].x);
+    BminY = Math.min(BminY, pointsB[i].y);
+    BmaxX = Math.max(BmaxX, pointsB[i].x);
+    BmaxY = Math.max(BmaxY, pointsB[i].y);
+  }
+  
+  if(((AminX <= BminX && BminX <= AmaxX) || (BminX <= AminX && AminX <= BmaxX)) && 
+     ((AminY <= BminY && BminY <= AmaxY) || (BminY <= AminY && AminY <= BmaxY))) {
+    // now let's be more specific
+    var polyA = pointsA.slice();
+    var polyB = pointsB.slice();
+    polyA.push(pointsA[0]);
+    polyB.push(pointsB[0]);
+  
+    // see if edges cross, or one contained in the other	
+    var deltaAX = [];
+    var deltaAY = [];
+    var deltaBX = [];
+    var deltaBY = [];
+    var rA = [];
+    var rB = [];
+    for(i = 0 ; i <= polyA.length - 2 ; i++){
+      deltaAX[i] = polyA[i+1].x - polyA[i].x;
+      deltaAY[i] = polyA[i+1].y - polyA[i].y;
+      //equation written as deltaY.x - deltaX.y + r = 0
+      rA[i] = deltaAX[i] * polyA[i].y - deltaAY[i] * polyA[i].x;
+    }
+    for(i = 0 ; i <= polyB.length - 2 ; i++){
+      deltaBX[i] = polyB[i+1].x - polyB[i].x;
+      deltaBY[i] = polyB[i+1].y - polyB[i].y;
+      rB[i] = deltaBX[i] * polyB[i].y - deltaBY[i] * polyB[i].x;
+    }
+  
+    for(i = 0 ; i <= polyA.length - 2 ; i++){
+      for(j = 0 ; j <= polyB.length - 2 ; j++){
+        if(deltaAX[i] * deltaBY[j] != deltaAY[i] * deltaBX[j]){
+          //case when vectors are colinear, or one polygon included in the other, is covered after
+          //two segments cross each other if and only if the points of the first are on each side of the line defined by the second and vice-versa
+          if((deltaAY[i] * polyB[j].x - deltaAX[i] * polyB[j].y + rA[i]) * (deltaAY[i] * polyB[j+1].x - deltaAX[i] * polyB[j+1].y + rA[i]) < -0.000000001 &&  
+             (deltaBY[j] * polyA[i].x - deltaBX[j] * polyA[i].y + rB[j]) * (deltaBY[j] * polyA[i+1].x - deltaBX[j] * polyA[i+1].y + rB[j]) < -0.000000001){
+            return true;
+          }
+        }
+      }
+    }
+  
+    for(i = 0 ; i <= polyA.length - 2 ; i++){
+      if(isPointInPoly(polyB, {x:polyA[i].x, y:polyA[i].y})){
+        return true;
+      }
+    }
+    for(i = 0 ; i <= polyB.length - 2 ; i++){
+      if(isPointInPoly(polyA, {x:polyB[i].x, y:polyB[i].y})){
+        return true;
+      }
+    }
+  
+    return false;
+  } else {
+    return false;
+  }
+
+};
+
 /**
  * Adds a path to the scene
  */
diff --git a/js/path.js b/js/path.js
index 3ed803c..739a67c 100644
--- a/js/path.js
+++ b/js/path.js
@@ -87,6 +87,53 @@ Path.prototype.depth = function () {
   return total / (this.points.length || 1);
 };
 
+/**
+ * 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 result = pathA._countCloserThan(this, observer) - this._countCloserThan(pathA, observer);
+  return result;
+}
+  
+Path.prototype._countCloserThan = function(pathA, observer) {
+  var Vector = Isomer.Vector;
+  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;
+  var result = 0;
+  var result0 = 0;
+  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 >= 0.000000001){ //careful with rounding approximations
+      result++;
+    }
+    if(observerPosition * pPosition >= -0.000000001 && observerPosition * pPosition < 0.000000001){
+      result0++;
+    }
+  }
+
+  if(result == 0){
+    return 0;
+  } else {
+    return ((result + result0) / this.points.length); 
+  }
+};
+  
+
+
 
 /**
  * Some paths to play with