1 files changed, 46 insertions, 1 deletions
diff --git a/o3d/samples/o3d-webgl/draw_list.js b/o3d/samples/o3d-webgl/draw_list.js
index 875f237..6132a8b 100644
--- a/o3d/samples/o3d-webgl/draw_list.js
+++ b/o3d/samples/o3d-webgl/draw_list.js
@@ -69,10 +69,55 @@ o3d.DrawList.BY_PRIORITY = 2;
 
 
 /**
+ * Compare function for by-priority sort.
+ */
+o3d.DrawList.comparePriority_ = function(drawElementInfoA, drawElementInfoB) {
+  return drawElementInfoA.drawElement.owner.priority -
+         drawElementInfoB.drawElement.owner.priority;
+};
+
+
+/**
+ * Compare function for by-z-coordinate sort.
+ * @param {!o3d.DrawElement} drawElementInfoA
+ * @param {!o3d.DrawElement} drawElementInfoB
+ */
+o3d.DrawList.compareZ_ = function(drawElementInfoA, drawElementInfoB) {
+  return o3d.Transform.transformPointZOnly(
+            drawElementInfoA.worldViewProjection,
+            drawElementInfoA.drawElement.owner.zSortPoint) -
+         o3d.Transform.transformPointZOnly(
+            drawElementInfoB.worldViewProjection,
+            drawElementInfoB.drawElement.owner.zSortPoint);
+};
+
+
+/**
+ * Sorts this list according to the given sort method.
+ * @param {o3d.DrawList.SortMethod} sort_method Which method to use.
+ * @private
+ */
+o3d.DrawList.prototype.sort_ = function(sort_method) {
+  switch (sort_method) {
+    case o3d.DrawList.BY_PRIORITY:
+      this.list_.sort(o3d.DrawList.comparePriority_);
+      break;
+
+    case o3d.DrawList.BY_Z_ORDER:
+      this.list_.sort(o3d.DrawList.compareZ_);
+      break;
+
+    case o3d.DrawList.BY_PERFORMANCE:
+    default:
+      break;
+  }
+};
+
+
+/**
  * Renders the draw list.
  */
 o3d.DrawList.prototype.render = function() {
-  // TODO(petersont): Add sort.
   for (var i = 0; i < this.list_.length; ++i) {
     var drawElementInfo = this.list_[i];
     var world = drawElementInfo.world;