WIP BSP Tree for 3D Layer Sorting

cc/output/bsp_controller.h

Index: cc/output/bsp_controller.h
diff --git a/cc/output/bsp_controller.h b/cc/output/bsp_controller.h
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+// 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_CONTROLLER_H_
+#define CC_OUTPUT_BSP_CONTROLLER_H_
+
+#include "cc/output/bsp_compare_result.h"
+#include "cc/quads/draw_polygon.h"
+
+namespace cc {
+
+// Specialization of the BSP Controller abstract class that deals specifically
+// with DrawPolygons
+class BspController {
+ public:
+  BspController();
+
+  // 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);
+  static bool SplitPolygon(scoped_ptr<DrawPolygon> polygon,
+                           const DrawPolygon& splitter,
+                           scoped_ptr<DrawPolygon>* front,
+                           scoped_ptr<DrawPolygon>* back);
+
+  // This heuristic uses the surface area of the polygon to determine whether
+  // or not a polygon is a good splitter. The idea is that if a polygon is
+  // larger, it is more likely to cross the planes of many other polygons,
+  // so using it as a splitter instead avoids many unnecessary splits.
+  virtual float SplitWeight(const DrawPolygon& polygon);
+
+  // This threshold controls how "thick" a plane is. If a point's distance is
+  // <= compare_threshold, then it is considered on the plane. Only when this
+  // boundary is crossed do we consider doing splitting.
+  static float compare_threshold;
+  static float split_threshold;
+};
+
+}  // namespace cc
+
+#endif  // CC_OUTPUT_BSP_CONTROLLER_H_