cc/output/bsp_tree.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "cc/output/bsp_tree.h"
   6
   7 #include <vector>
   8
   9 #include "base/memory/scoped_ptr.h"
  10 #include "cc/base/scoped_ptr_deque.h"
  11 #include "cc/base/scoped_ptr_vector.h"
  12 #include "cc/output/bsp_compare_result.h"
  13 #include "cc/quads/draw_polygon.h"
  14
  15 namespace cc {
  16
  17 BspNode::BspNode(scoped_ptr<DrawPolygon> data) : node_data(data.Pass()) {
  18 }
  19
  20 BspNode::~BspNode() {
  21 }
  22
  23 BspTree::BspTree(ScopedPtrDeque<DrawPolygon>* list) {
  24   if (list->size() == 0)
  25     return;
  26
  27   root_ = make_scoped_ptr(new BspNode(list->take_front()));
  28   BuildTree(root_.get(), list);
  29 }
  30
  31 // The idea behind using a deque for BuildTree's input is that we want to be
  32 // able to place polygons that we've decided aren't splitting plane candidates
  33 // at the back of the queue while moving the candidate splitting planes to the
  34 // front when the heuristic decides that they're a better choice. This way we
  35 // can always simply just take from the front of the deque for our node's
  36 // data.
  37 void BspTree::BuildTree(BspNode* node,
  38                         ScopedPtrDeque<DrawPolygon>* polygon_list) {
  39   ScopedPtrDeque<DrawPolygon> front_list;
  40   ScopedPtrDeque<DrawPolygon> back_list;
  41
  42   // We take in a list of polygons at this level of the tree, and have to
  43   // find a splitting plane, then classify polygons as either in front of
  44   // or behind that splitting plane.
  45   while (polygon_list->size() > 0) {
  46     // Is this particular polygon in front of or behind our splitting polygon.
  47     BspCompareResult comparer_result =
  48         GetNodePositionRelative(*polygon_list->front(), *(node->node_data));
  49
  50     // If it's clearly behind or in front of the splitting plane, we use the
  51     // heuristic to decide whether or not we should put it at the back
  52     // or front of the list.
  53     switch (comparer_result) {
  54       case BSP_FRONT:
  55         front_list.push_back(polygon_list->take_front().Pass());
  56         break;
  57       case BSP_BACK:
  58         back_list.push_back(polygon_list->take_front().Pass());
  59         break;
  60       case BSP_SPLIT:
  61       {
  62         scoped_ptr<DrawPolygon> polygon;
  63         scoped_ptr<DrawPolygon> new_front;
  64         scoped_ptr<DrawPolygon> new_back;
  65         bool split_result = false;
  66         // Time to split this geometry, *it needs to be split by node_data.
  67         polygon = polygon_list->take_front();
  68         split_result =
  69             polygon->Split(*(node->node_data), &new_front, &new_back);
  70         DCHECK(split_result);
  71         if (!split_result) {
  72           break;
  73         }
  74         front_list.push_back(new_front.Pass());
  75         back_list.push_back(new_back.Pass());
  76         break;
  77       }
  78       case BSP_COPLANAR_FRONT:
  79         node->coplanars_front.push_back(polygon_list->take_front());
  80         break;
  81       case BSP_COPLANAR_BACK:
  82         node->coplanars_back.push_back(polygon_list->take_front());
  83         break;
  84       default:
  85         NOTREACHED();
  86         break;
  87     }
  88   }
  89
  90   // Build the back subtree using the front of the back_list as our splitter.
  91   if (back_list.size() > 0) {
  92     node->back_child = make_scoped_ptr(new BspNode(back_list.take_front()));
  93     BuildTree(node->back_child.get(), &back_list);
  94   }
  95
  96   // Build the front subtree using the front of the front_list as our splitter.
  97   if (front_list.size() > 0) {
  98     node->front_child =
  99         scoped_ptr<BspNode>(new BspNode(front_list.take_front()));
 100     BuildTree(node->front_child.get(), &front_list);
 101   }
 102 }
 103
 104 BspCompareResult BspTree::GetNodePositionRelative(const DrawPolygon& node_a,
 105                                                   const DrawPolygon& node_b) {
 106   return DrawPolygon::SideCompare(node_a, node_b);
 107 }
 108
 109 // The base comparer with 0,0,0 as camera position facing forward
 110 BspCompareResult BspTree::GetCameraPositionRelative(const DrawPolygon& node) {
 111   if (node.normal().z() > 0.0f) {
 112     return BSP_FRONT;
 113   }
 114   return BSP_BACK;
 115 }
 116
 117 BspTree::~BspTree() {
 118 }
 119
 120 }  // namespace cc