WIP BSP Tree for 3D Layer Sorting

cc/output/bsp_controller.cc

+// 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.
+#include "cc/output/bsp_compare_result.h"
+#include "cc/output/bsp_controller.h"
+#include "cc/quads/draw_polygon.h"
+#include "ui/gfx/vector3d_f.h"
+
+namespace cc {
+
+BspController::BspController() {
+}
+
+static gfx::Point3F camera_point(0.0f, 0.0f, 0.0f);

[Ian Vollick, 2014/07/19 00:45:01]

I think that this counts as a static initializer, which is discouraged in
chromium code. You should feel completely justified passing in gfx::Point3F()
whenever you need the camera's position rather than using this variable.

[troyhildebrandt, 2014/07/21 19:16:50]

Done.

+float BspController::compare_threshold = 1.0f;
+float BspController::split_threshold = 0.5f;
+
+BspCompareResult BspController::GetNodePositionRelative(
+    const DrawPolygon& node_a,
+    const DrawPolygon& node_b) {
+  return DrawPolygon::SideCompare(node_a, node_b, compare_threshold);
+}
+
+// The base comparer with 0,0,0 as camera position facing forward
+BspCompareResult BspController::GetCameraPositionRelative(
+    const DrawPolygon& node) {
+  // The dot product figures out if we're behind or in front of the
+  // current DrawPolygon based on its normal and a point from it.
+  gfx::Vector3dF camera_minus_point_on_plane = camera_point - node.points[0];
+  if (gfx::DotProduct(camera_minus_point_on_plane, node.normal) > 0.0f) {
+    return BSP_FRONT;
+  }
+  return BSP_BACK;
+}
+
+bool BspController::SplitPolygon(scoped_ptr<DrawPolygon> polygon,
+                                 const DrawPolygon& splitter,
+                                 scoped_ptr<DrawPolygon>* front,
+                                 scoped_ptr<DrawPolygon>* back) {
+  return polygon->Split(splitter, split_threshold, front, back);
+}
+
+float BspController::SplitWeight(const DrawPolygon& polygon) {
+  return polygon.area;
+}
+
+}  // namespace cc