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// 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.
#include "cc/output/bsp_tree.h"
#include <vector>
#include "base/memory/scoped_ptr.h"
#include "cc/base/container_util.h"
#include "cc/output/bsp_compare_result.h"
#include "cc/quads/draw_polygon.h"
namespace cc {
BspNode::BspNode(scoped_ptr<DrawPolygon> data) : node_data(std::move(data)) {}
BspNode::~BspNode() {
}
BspTree::BspTree(std::deque<scoped_ptr<DrawPolygon>>* list) {
if (list->size() == 0)
return;
root_ = make_scoped_ptr(new BspNode(PopFront(list)));
BuildTree(root_.get(), list);
}
// The idea behind using a deque for BuildTree's input is that we want to be
// able to place polygons that we've decided aren't splitting plane candidates
// at the back of the queue while moving the candidate splitting planes to the
// front when the heuristic decides that they're a better choice. This way we
// can always simply just take from the front of the deque for our node's
// data.
void BspTree::BuildTree(BspNode* node,
std::deque<scoped_ptr<DrawPolygon>>* polygon_list) {
std::deque<scoped_ptr<DrawPolygon>> front_list;
std::deque<scoped_ptr<DrawPolygon>> back_list;
// We take in a list of polygons at this level of the tree, and have to
// find a splitting plane, then classify polygons as either in front of
// or behind that splitting plane.
while (!polygon_list->empty()) {
// Is this particular polygon in front of or behind our splitting polygon.
BspCompareResult comparer_result =
GetNodePositionRelative(*polygon_list->front(), *(node->node_data));
// If it's clearly behind or in front of the splitting plane, we use the
// heuristic to decide whether or not we should put it at the back
// or front of the list.
switch (comparer_result) {
case BSP_FRONT:
front_list.push_back(PopFront(polygon_list));
break;
case BSP_BACK:
back_list.push_back(PopFront(polygon_list));
break;
case BSP_SPLIT:
{
scoped_ptr<DrawPolygon> polygon;
scoped_ptr<DrawPolygon> new_front;
scoped_ptr<DrawPolygon> new_back;
// Time to split this geometry, *it needs to be split by node_data.
polygon = PopFront(polygon_list);
bool split_result =
polygon->Split(*(node->node_data), &new_front, &new_back);
DCHECK(split_result);
if (!split_result) {
break;
}
front_list.push_back(std::move(new_front));
back_list.push_back(std::move(new_back));
break;
}
case BSP_COPLANAR_FRONT:
node->coplanars_front.push_back(PopFront(polygon_list));
break;
case BSP_COPLANAR_BACK:
node->coplanars_back.push_back(PopFront(polygon_list));
break;
default:
NOTREACHED();
break;
}
}
// Build the back subtree using the front of the back_list as our splitter.
if (back_list.size() > 0) {
node->back_child = make_scoped_ptr(new BspNode(PopFront(&back_list)));
BuildTree(node->back_child.get(), &back_list);
}
// Build the front subtree using the front of the front_list as our splitter.
if (front_list.size() > 0) {
node->front_child = make_scoped_ptr(new BspNode(PopFront(&front_list)));
BuildTree(node->front_child.get(), &front_list);
}
}
BspCompareResult BspTree::GetNodePositionRelative(const DrawPolygon& node_a,
const DrawPolygon& node_b) {
return DrawPolygon::SideCompare(node_a, node_b);
}
// The base comparer with 0,0,0 as camera position facing forward
BspCompareResult BspTree::GetCameraPositionRelative(const DrawPolygon& node) {
if (node.normal().z() > 0.0f) {
return BSP_FRONT;
}
return BSP_BACK;
}
BspTree::~BspTree() {
}
} // namespace cc
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