WIP BSP Tree for 3D Layer Sorting

cc/output/bsp_tree.h

Index: cc/output/bsp_tree.h
diff --git a/cc/output/bsp_tree.h b/cc/output/bsp_tree.h
new file mode 100644
index 0000000000000000000000000000000000000000..cd1ec7195da8440cfa276552598ec5e497a3f82e
--- /dev/null
+++ b/cc/output/bsp_tree.h
@@ -0,0 +1,101 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CC_OUTPUT_BSP_TREE_H_
+#define CC_OUTPUT_BSP_TREE_H_
+
+#include <list>
+#include <vector>
+
+#include "base/memory/scoped_ptr.h"
+#include "cc/base/scoped_ptr_deque.h"
+#include "cc/base/scoped_ptr_vector.h"
+#include "cc/output/bsp_compare_result.h"
+#include "cc/output/bsp_controller.h"
+#include "cc/quads/draw_polygon.h"
+
+namespace cc {
+
+struct BspNode {
+  // This represents the splitting plane.
+  scoped_ptr<DrawPolygon> node_data;
+  // This represents any coplanar geometry we found while building the BSP.
+  ScopedPtrVector<DrawPolygon> coplanars_front;
+  ScopedPtrVector<DrawPolygon> coplanars_back;
+
+  scoped_ptr<BspNode> back_child;
+  scoped_ptr<BspNode> front_child;
+
+  explicit BspNode(scoped_ptr<DrawPolygon> data);
+  ~BspNode();
+};
+
+class BspTree {
+ private:
+  scoped_ptr<BspNode> root_;
+  BspController* controller_;
+
+  void FromList(ScopedPtrVector<DrawPolygon>* list);

[Ian Vollick, 2014/07/16 20:54:33]

Would be nice to add comment explaining the difference between these two
functions.

[troyhildebrandt, 2014/07/18 21:48:26]

Done.

+  void BuildTree(const scoped_ptr<BspNode>& node,
+                 ScopedPtrDeque<DrawPolygon>* data);
+
+  template <typename ActionHandlerType>
+  void WalkInOrderAction(ActionHandlerType* action_handler,
+                         DrawPolygon* item) const {

[Ian Vollick, 2014/07/16 20:54:33]

If you define these templatized member functions outside the class, I think you
could order public before private in the usual way and improve readability.

[troyhildebrandt, 2014/07/18 21:48:26]

Simply changed the ordering, no complaints from the compiler. Not sure why I had
ordered it that way in the first place. Long story short: done.

+    (*action_handler)(item);
+  }
+
+  template <typename ActionHandlerType>
+  void WalkInOrderRecursion(ActionHandlerType* action_handler,
+                            const scoped_ptr<BspNode>& node) const {
+    // If our view is in front of the the polygon
+    // in this node then walk back then front.

[Ian Vollick, 2014/07/16 20:54:33]

Could this be made more concise by storing node ptrs for |first| and |second|
nodes and coplanar arrays conditionally upon GetCameraPositionRelative? That
would let you use the same traversal code for all of them.

[troyhildebrandt, 2014/07/18 21:48:26]

Done.

+    if (controller_->GetCameraPositionRelative(*(node->node_data)) ==
+        IN_FRONT) {
+      if (node->back_child)
+        WalkInOrderRecursion(action_handler, node->back_child);
+      // Add all items from this node level to the list in their current order.
+      for (unsigned int i = 0; i < node->coplanars_front.size(); i++) {
+        WalkInOrderAction(action_handler, node->coplanars_front[i]);
+      }
+      WalkInOrderAction(action_handler, node->node_data.get());
+      for (unsigned int i = 0; i < node->coplanars_back.size(); i++) {
+        WalkInOrderAction(action_handler, node->coplanars_back[i]);
+      }
+      if (node->front_child)
+        WalkInOrderRecursion(action_handler, node->front_child);
+    } else {
+      if (node->front_child)
+        WalkInOrderRecursion(action_handler, node->front_child);
+      // Add all items from this node level to the list in their current order.
+      for (unsigned int i = 0; i < node->coplanars_back.size(); i++) {
+        WalkInOrderAction(action_handler, node->coplanars_back[i]);
+      }
+      WalkInOrderAction(action_handler, node->node_data.get());
+      for (unsigned int i = 0; i < node->coplanars_front.size(); i++) {
+        WalkInOrderAction(action_handler, node->coplanars_front[i]);
+      }
+      if (node->back_child)
+        WalkInOrderRecursion(action_handler, node->back_child);
+    }
+  }
+
+ public:
+  BspTree(BspController* bsp_controller, ScopedPtrVector<DrawPolygon>* list);
+  scoped_ptr<BspNode>& root() { return root_; }
+
+  template <typename ActionHandlerType>
+  void TraverseWithActionHandler(ActionHandlerType* action_handler) const {
+    if (root_) {
+      WalkInOrderRecursion<ActionHandlerType>(action_handler, root_);
+    }
+  }
+
+  void Clear();
+  ~BspTree();
+};
+
+}  // namespace cc
+
+#endif  // CC_OUTPUT_BSP_TREE_H_