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