WIP BSP Tree for 3D Layer Sorting

cc/output/bsp_tree.h

+// Copyright 2014 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/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 {
+ public:
+  explicit BspTree(ScopedPtrDeque<DrawPolygon>* list);
+  scoped_ptr<BspNode>& root() { return root_; }
+
+  template <typename ActionHandlerType>
+  void TraverseWithActionHandler(ActionHandlerType* action_handler) const {
+    if (root_) {
+      WalkInOrderRecursion<ActionHandlerType>(action_handler, root_.get());
+    }
+  }
+
+  ~BspTree();
+
+ private:
+  scoped_ptr<BspNode> root_;
+
+  void FromList(ScopedPtrVector<DrawPolygon>* list);
+  void BuildTree(BspNode* node, ScopedPtrDeque<DrawPolygon>* data);
+
+  template <typename ActionHandlerType>
+  void WalkInOrderAction(ActionHandlerType* action_handler,
+                         DrawPolygon* item) const {
+    (*action_handler)(item);
+  }
+
+  template <typename ActionHandlerType>
+  void WalkInOrderVisitNodes(
+      ActionHandlerType* action_handler,
+      const BspNode* node,
+      const BspNode* first_child,
+      const BspNode* second_child,
+      const ScopedPtrVector<DrawPolygon>& first_coplanars,
+      const ScopedPtrVector<DrawPolygon>& second_coplanars) const {
+    if (first_child) {
+      WalkInOrderRecursion(action_handler, first_child);
+    }
+    for (size_t i = 0; i < first_coplanars.size(); i++) {
+      WalkInOrderAction(action_handler, first_coplanars[i]);
+    }
+    WalkInOrderAction(action_handler, node->node_data.get());
+    for (size_t i = 0; i < second_coplanars.size(); i++) {
+      WalkInOrderAction(action_handler, second_coplanars[i]);
+    }
+    if (second_child) {
+      WalkInOrderRecursion(action_handler, second_child);
+    }
+  }
+
+  template <typename ActionHandlerType>
+  void WalkInOrderRecursion(ActionHandlerType* action_handler,
+                            const BspNode* node) const {
+    // If our view is in front of the the polygon
+    // in this node then walk back then front.
+    if (GetCameraPositionRelative(*(node->node_data)) == BSP_FRONT) {
+      WalkInOrderVisitNodes<ActionHandlerType>(action_handler,
+                                               node,
+                                               node->back_child.get(),
+                                               node->front_child.get(),
+                                               node->coplanars_front,
+                                               node->coplanars_back);
+    } else {
+      WalkInOrderVisitNodes<ActionHandlerType>(action_handler,
+                                               node,
+                                               node->front_child.get(),
+                                               node->back_child.get(),
+                                               node->coplanars_back,
+                                               node->coplanars_front);
+    }
+  }
+
+  // Returns whether or not nodeA is on one or the other side of nodeB,
+  // coplanar, or whether it crosses nodeB's plane and needs to be split
+  static BspCompareResult GetNodePositionRelative(const DrawPolygon& node_a,
+                                                  const DrawPolygon& node_b);
+  // Returns whether or not our viewer is in front of or behind the plane
+  // defined by this polygon/node
+  static BspCompareResult GetCameraPositionRelative(const DrawPolygon& node);
+};
+
+}  // namespace cc
+
+#endif  // CC_OUTPUT_BSP_TREE_H_