107 lines
3.0 KiB
C++
107 lines
3.0 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef MOZILLA_LAYERS_BSPTREE_H
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#define MOZILLA_LAYERS_BSPTREE_H
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#include "mozilla/gfx/Polygon.h"
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#include "mozilla/Move.h"
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#include "mozilla/UniquePtr.h"
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#include "nsTArray.h"
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#include <deque>
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namespace mozilla {
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namespace layers {
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class Layer;
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// Represents a layer that might have a non-rectangular geometry.
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struct LayerPolygon {
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explicit LayerPolygon(Layer *aLayer)
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: layer(aLayer) {}
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LayerPolygon(Layer *aLayer,
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gfx::Polygon3D&& aGeometry)
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: layer(aLayer), geometry(Some(aGeometry)) {}
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LayerPolygon(Layer *aLayer,
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nsTArray<gfx::Point3D>&& aPoints, const gfx::Point3D& aNormal)
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: layer(aLayer), geometry(Some(gfx::Polygon3D(Move(aPoints), aNormal))) {}
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Layer *layer;
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Maybe<gfx::Polygon3D> geometry;
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};
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LayerPolygon PopFront(std::deque<LayerPolygon>& aLayers);
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// Represents a node in a BSP tree. The node contains at least one layer with
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// associated geometry that is used as a splitting plane, and at most two child
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// nodes that represent the splitting planes that further subdivide the space.
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struct BSPTreeNode {
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explicit BSPTreeNode(LayerPolygon&& layer)
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{
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layers.push_back(Move(layer));
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}
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const gfx::Polygon3D& First() const
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{
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MOZ_ASSERT(layers[0].geometry);
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return *layers[0].geometry;
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}
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UniquePtr<BSPTreeNode> front;
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UniquePtr<BSPTreeNode> back;
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std::deque<LayerPolygon> layers;
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};
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// BSPTree class takes a list of layers as an input and uses binary space
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// partitioning algorithm to create a tree structure that can be used for
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// depth sorting.
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//
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// Sources for more information:
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// https://en.wikipedia.org/wiki/Binary_space_partitioning
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// ftp://ftp.sgi.com/other/bspfaq/faq/bspfaq.html
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class BSPTree {
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public:
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// This constructor takes the ownership of layers in the given list.
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explicit BSPTree(std::deque<LayerPolygon>& aLayers)
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{
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MOZ_ASSERT(!aLayers.empty());
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mRoot.reset(new BSPTreeNode(PopFront(aLayers)));
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BuildTree(mRoot, aLayers);
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}
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// Returns the root node of the BSP tree.
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const UniquePtr<BSPTreeNode>& GetRoot() const
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{
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return mRoot;
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}
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// Builds and returns the back-to-front draw order for the created BSP tree.
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nsTArray<LayerPolygon> GetDrawOrder() const
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{
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nsTArray<LayerPolygon> layers;
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BuildDrawOrder(mRoot, layers);
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return layers;
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}
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private:
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UniquePtr<BSPTreeNode> mRoot;
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// BuildDrawOrder and BuildTree are called recursively. The depth of the
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// recursion depends on the amount of polygons and their intersections.
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void BuildDrawOrder(const UniquePtr<BSPTreeNode>& aNode,
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nsTArray<LayerPolygon>& aLayers) const;
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void BuildTree(UniquePtr<BSPTreeNode>& aRoot,
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std::deque<LayerPolygon>& aLayers);
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};
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} // namespace layers
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} // namespace mozilla
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#endif /* MOZILLA_LAYERS_BSPTREE_H */
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