Add a Dynamic BVH implementation.

-Based on Bullet Dbvh, has style and functional changes.
-Provides efficient pairing
-Needed to optimize rendering
-Needed to optimize physics

This PR is up for others to review the implementation.

core/math/dynamic_bvh.cpp

@@ -0,0 +1,400 @@
+/*************************************************************************/
+/*  dynamic_bvh.cpp                                                      */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2020 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+#include "dynamic_bvh.h"
+
+void DynamicBVH::_delete_node(Node *p_node) {
+	memdelete(p_node);
+}
+
+void DynamicBVH::_recurse_delete_node(Node *p_node) {
+	if (!p_node->is_leaf()) {
+		_recurse_delete_node(p_node->childs[0]);
+		_recurse_delete_node(p_node->childs[1]);
+	}
+	if (p_node == bvh_root) {
+		bvh_root = nullptr;
+	}
+	_delete_node(p_node);
+}
+
+DynamicBVH::Node *DynamicBVH::_create_node(Node *p_parent, void *p_data) {
+	Node *node = memnew(Node);
+	node->parent = p_parent;
+	node->data = p_data;
+	node->childs[1] = 0;
+	return (node);
+}
+
+DynamicBVH::Node *DynamicBVH::_create_node_with_volume(Node *p_parent, const Volume &p_volume, void *p_data) {
+	Node *node = _create_node(p_parent, p_data);
+	node->volume = p_volume;
+	return node;
+}
+
+void DynamicBVH::_insert_leaf(Node *p_root, Node *p_leaf) {
+	if (!bvh_root) {
+		bvh_root = p_leaf;
+		p_leaf->parent = 0;
+	} else {
+		if (!p_root->is_leaf()) {
+			do {
+				p_root = p_root->childs[p_leaf->volume.select_by_proximity(
+						p_root->childs[0]->volume,
+						p_root->childs[1]->volume)];
+			} while (!p_root->is_leaf());
+		}
+		Node *prev = p_root->parent;
+		Node *node = _create_node_with_volume(prev, p_leaf->volume.merge(p_root->volume), 0);
+		if (prev) {
+			prev->childs[p_root->get_index_in_parent()] = node;
+			node->childs[0] = p_root;
+			p_root->parent = node;
+			node->childs[1] = p_leaf;
+			p_leaf->parent = node;
+			do {
+				if (!prev->volume.contains(node->volume)) {
+					prev->volume = prev->childs[0]->volume.merge(prev->childs[1]->volume);
+				} else {
+					break;
+				}
+				node = prev;
+			} while (0 != (prev = node->parent));
+		} else {
+			node->childs[0] = p_root;
+			p_root->parent = node;
+			node->childs[1] = p_leaf;
+			p_leaf->parent = node;
+			bvh_root = node;
+		}
+	}
+}
+
+DynamicBVH::Node *DynamicBVH::_remove_leaf(Node *leaf) {
+	if (leaf == bvh_root) {
+		bvh_root = 0;
+		return (0);
+	} else {
+		Node *parent = leaf->parent;
+		Node *prev = parent->parent;
+		Node *sibling = parent->childs[1 - leaf->get_index_in_parent()];
+		if (prev) {
+			prev->childs[parent->get_index_in_parent()] = sibling;
+			sibling->parent = prev;
+			_delete_node(parent);
+			while (prev) {
+				const Volume pb = prev->volume;
+				prev->volume = prev->childs[0]->volume.merge(prev->childs[1]->volume);
+				if (pb.is_not_equal_to(prev->volume)) {
+					prev = prev->parent;
+				} else
+					break;
+			}
+			return (prev ? prev : bvh_root);
+		} else {
+			bvh_root = sibling;
+			sibling->parent = 0;
+			_delete_node(parent);
+			return (bvh_root);
+		}
+	}
+}
+
+void DynamicBVH::_fetch_leaves(Node *p_root, LocalVector<Node *> &r_leaves, int p_depth) {
+	if (p_root->is_internal() && p_depth) {
+		_fetch_leaves(p_root->childs[0], r_leaves, p_depth - 1);
+		_fetch_leaves(p_root->childs[1], r_leaves, p_depth - 1);
+		_delete_node(p_root);
+	} else {
+		r_leaves.push_back(p_root);
+	}
+}
+
+// Partitions leaves such that leaves[0, n) are on the
+// left of axis, and leaves[n, count) are on the right
+// of axis. returns N.
+int DynamicBVH::_split(Node **leaves, int p_count, const Vector3 &p_org, const Vector3 &p_axis) {
+	int begin = 0;
+	int end = p_count;
+	for (;;) {
+		while (begin != end && leaves[begin]->is_left_of_axis(p_org, p_axis)) {
+			++begin;
+		}
+
+		if (begin == end) {
+			break;
+		}
+
+		while (begin != end && !leaves[end - 1]->is_left_of_axis(p_org, p_axis)) {
+			--end;
+		}
+
+		if (begin == end) {
+			break;
+		}
+
+		// swap out of place nodes
+		--end;
+		Node *temp = leaves[begin];
+		leaves[begin] = leaves[end];
+		leaves[end] = temp;
+		++begin;
+	}
+
+	return begin;
+}
+
+DynamicBVH::Volume DynamicBVH::_bounds(Node **leaves, int p_count) {
+	Volume volume = leaves[0]->volume;
+	for (int i = 1, ni = p_count; i < ni; ++i) {
+		volume = volume.merge(leaves[i]->volume);
+	}
+	return (volume);
+}
+
+void DynamicBVH::_bottom_up(Node **leaves, int p_count) {
+	while (p_count > 1) {
+		real_t minsize = Math_INF;
+		int minidx[2] = { -1, -1 };
+		for (int i = 0; i < p_count; ++i) {
+			for (int j = i + 1; j < p_count; ++j) {
+				const real_t sz = leaves[i]->volume.merge(leaves[j]->volume).get_size();
+				if (sz < minsize) {
+					minsize = sz;
+					minidx[0] = i;
+					minidx[1] = j;
+				}
+			}
+		}
+		Node *n[] = { leaves[minidx[0]], leaves[minidx[1]] };
+		Node *p = _create_node_with_volume(nullptr, n[0]->volume.merge(n[1]->volume), nullptr);
+		p->childs[0] = n[0];
+		p->childs[1] = n[1];
+		n[0]->parent = p;
+		n[1]->parent = p;
+		leaves[minidx[0]] = p;
+		leaves[minidx[1]] = leaves[p_count - 1];
+		--p_count;
+	}
+}
+
+DynamicBVH::Node *DynamicBVH::_top_down(Node **leaves, int p_count, int p_bu_threshold) {
+	static const Vector3 axis[] = { Vector3(1, 0, 0), Vector3(0, 1, 0), Vector3(0, 0, 1) };
+
+	ERR_FAIL_COND_V(p_bu_threshold <= 1, nullptr);
+	if (p_count > 1) {
+		if (p_count > p_bu_threshold) {
+			const Volume vol = _bounds(leaves, p_count);
+			const Vector3 org = vol.get_center();
+			int partition;
+			int bestaxis = -1;
+			int bestmidp = p_count;
+			int splitcount[3][2] = { { 0, 0 }, { 0, 0 }, { 0, 0 } };
+			int i;
+			for (i = 0; i < p_count; ++i) {
+				const Vector3 x = leaves[i]->volume.get_center() - org;
+				for (int j = 0; j < 3; ++j) {
+					++splitcount[j][x.dot(axis[j]) > 0 ? 1 : 0];
+				}
+			}
+			for (i = 0; i < 3; ++i) {
+				if ((splitcount[i][0] > 0) && (splitcount[i][1] > 0)) {
+					const int midp = (int)Math::abs(real_t(splitcount[i][0] - splitcount[i][1]));
+					if (midp < bestmidp) {
+						bestaxis = i;
+						bestmidp = midp;
+					}
+				}
+			}
+			if (bestaxis >= 0) {
+				partition = _split(leaves, p_count, org, axis[bestaxis]);
+				ERR_FAIL_COND_V(partition == 0 || partition == p_count, nullptr);
+			} else {
+				partition = p_count / 2 + 1;
+			}
+
+			Node *node = _create_node_with_volume(nullptr, vol, nullptr);
+			node->childs[0] = _top_down(&leaves[0], partition, p_bu_threshold);
+			node->childs[1] = _top_down(&leaves[partition], p_count - partition, p_bu_threshold);
+			node->childs[0]->parent = node;
+			node->childs[1]->parent = node;
+			return (node);
+		} else {
+			_bottom_up(leaves, p_count);
+			return (leaves[0]);
+		}
+	}
+	return (leaves[0]);
+}
+
+DynamicBVH::Node *DynamicBVH::_node_sort(Node *n, Node *&r) {
+	Node *p = n->parent;
+	ERR_FAIL_COND_V(!n->is_internal(), nullptr);
+	if (p > n) {
+		const int i = n->get_index_in_parent();
+		const int j = 1 - i;
+		Node *s = p->childs[j];
+		Node *q = p->parent;
+		ERR_FAIL_COND_V(n != p->childs[i], nullptr);
+		if (q)
+			q->childs[p->get_index_in_parent()] = n;
+		else
+			r = n;
+		s->parent = n;
+		p->parent = n;
+		n->parent = q;
+		p->childs[0] = n->childs[0];
+		p->childs[1] = n->childs[1];
+		n->childs[0]->parent = p;
+		n->childs[1]->parent = p;
+		n->childs[i] = p;
+		n->childs[j] = s;
+		SWAP(p->volume, n->volume);
+		return (p);
+	}
+	return (n);
+}
+
+void DynamicBVH::clear() {
+	if (bvh_root) {
+		_recurse_delete_node(bvh_root);
+	}
+	lkhd = -1;
+	opath = 0;
+}
+
+void DynamicBVH::optimize_bottom_up() {
+	if (bvh_root) {
+		LocalVector<Node *> leaves;
+		_fetch_leaves(bvh_root, leaves);
+		_bottom_up(&leaves[0], leaves.size());
+		bvh_root = leaves[0];
+	}
+}
+
+void DynamicBVH::optimize_top_down(int bu_threshold) {
+	if (bvh_root) {
+		LocalVector<Node *> leaves;
+		_fetch_leaves(bvh_root, leaves);
+		bvh_root = _top_down(&leaves[0], leaves.size(), bu_threshold);
+	}
+}
+
+void DynamicBVH::optimize_incremental(int passes) {
+	if (passes < 0)
+		passes = total_leaves;
+	if (bvh_root && (passes > 0)) {
+		do {
+			Node *node = bvh_root;
+			unsigned bit = 0;
+			while (node->is_internal()) {
+				node = _node_sort(node, bvh_root)->childs[(opath >> bit) & 1];
+				bit = (bit + 1) & (sizeof(unsigned) * 8 - 1);
+			}
+			_update(node);
+			++opath;
+		} while (--passes);
+	}
+}
+
+DynamicBVH::ID DynamicBVH::insert(const AABB &p_box, void *p_userdata) {
+	Volume volume;
+	volume.min = p_box.position;
+	volume.max = p_box.position + p_box.size;
+
+	Node *leaf = _create_node_with_volume(nullptr, volume, p_userdata);
+	_insert_leaf(bvh_root, leaf);
+	++total_leaves;
+
+	ID id;
+	id.node = leaf;
+	return id;
+}
+
+void DynamicBVH::_update(Node *leaf, int lookahead) {
+	Node *root = _remove_leaf(leaf);
+	if (root) {
+		if (lookahead >= 0) {
+			for (int i = 0; (i < lookahead) && root->parent; ++i) {
+				root = root->parent;
+			}
+		} else
+			root = bvh_root;
+	}
+	_insert_leaf(root, leaf);
+}
+
+void DynamicBVH::update(const ID &p_id, const AABB &p_box) {
+	ERR_FAIL_COND(!p_id.is_valid());
+	Node *leaf = p_id.node;
+	Node *base = _remove_leaf(leaf);
+	Volume volume;
+	volume.min = p_box.position;
+	volume.max = p_box.position + p_box.size;
+	if (base) {
+		if (lkhd >= 0) {
+			for (int i = 0; (i < lkhd) && base->parent; ++i) {
+				base = base->parent;
+			}
+		} else
+			base = bvh_root;
+	}
+	leaf->volume = volume;
+	_insert_leaf(base, leaf);
+}
+
+void DynamicBVH::remove(const ID &p_id) {
+	ERR_FAIL_COND(!p_id.is_valid());
+	Node *leaf = p_id.node;
+	_remove_leaf(leaf);
+	_delete_node(leaf);
+	--total_leaves;
+}
+
+void DynamicBVH::_extract_leaves(Node *p_node, List<ID> *r_elements) {
+	if (p_node->is_internal()) {
+		_extract_leaves(p_node->childs[0], r_elements);
+		_extract_leaves(p_node->childs[1], r_elements);
+	} else {
+		ID id;
+		id.node = p_node;
+		r_elements->push_back(id);
+	}
+}
+
+void DynamicBVH::get_elements(List<ID> *r_elements) {
+	if (bvh_root) {
+		_extract_leaves(bvh_root, r_elements);
+	}
+}
+
+DynamicBVH::~DynamicBVH() {
+	clear();
+}

core/math/dynamic_bvh.h

@@ -0,0 +1,359 @@
+/*************************************************************************/
+/*  dynamic_bvh.h                                                        */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2020 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+#ifndef DYNAMICBVH_H
+#define DYNAMICBVH_H
+
+#include "core/math/aabb.h"
+#include "core/templates/list.h"
+#include "core/templates/local_vector.h"
+#include "core/typedefs.h"
+
+// Based on bullet Dbvh
+
+/*
+Bullet Continuous Collision Detection and Physics Library
+Copyright (c) 2003-2013 Erwin Coumans  http://bulletphysics.org
+
+This software is provided 'as-is', without any express or implied warranty.
+In no event will the authors be held liable for any damages arising from the use of this software.
+Permission is granted to anyone to use this software for any purpose,
+including commercial applications, and to alter it and redistribute it freely,
+subject to the following restrictions:
+
+1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
+2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
+3. This notice may not be removed or altered from any source distribution.
+*/
+
+///DynamicBVH implementation by Nathanael Presson
+// The DynamicBVH class implements a fast dynamic bounding volume tree based on axis aligned bounding boxes (aabb tree).
+
+class DynamicBVH {
+	struct Node;
+
+public:
+	struct ID {
+		Node *node;
+
+	public:
+		_FORCE_INLINE_ bool is_valid() const { return node != nullptr; }
+		_FORCE_INLINE_ ID() {
+			node = nullptr;
+		}
+	};
+
+private:
+	struct Volume {
+		Vector3 min, max;
+
+		_FORCE_INLINE_ Vector3 get_center() const { return ((min + max) / 2); }
+		_FORCE_INLINE_ Vector3 get_length() const { return (max - min); }
+
+		_FORCE_INLINE_ bool contains(const Volume &a) const {
+			return ((min.x <= a.min.x) &&
+					(min.y <= a.min.y) &&
+					(min.z <= a.min.z) &&
+					(max.x >= a.max.x) &&
+					(max.y >= a.max.y) &&
+					(max.z >= a.max.z));
+		}
+
+		_FORCE_INLINE_ Volume merge(const Volume &b) const {
+			Volume r;
+			for (int i = 0; i < 3; ++i) {
+				if (min[i] < b.min[i])
+					r.min[i] = min[i];
+				else
+					r.min[i] = b.min[i];
+				if (max[i] > b.max[i])
+					r.max[i] = max[i];
+				else
+					r.max[i] = b.max[i];
+			}
+			return r;
+		}
+
+		_FORCE_INLINE_ real_t get_size() const {
+			const Vector3 edges = get_length();
+			return (edges.x * edges.y * edges.z +
+					edges.x + edges.y + edges.z);
+		}
+
+		_FORCE_INLINE_ bool is_not_equal_to(const Volume &b) const {
+			return ((min.x != b.min.x) ||
+					(min.y != b.min.y) ||
+					(min.z != b.min.z) ||
+					(max.x != b.max.x) ||
+					(max.y != b.max.y) ||
+					(max.z != b.max.z));
+		}
+
+		_FORCE_INLINE_ real_t get_proximity_to(const Volume &b) const {
+			const Vector3 d = (min + max) - (b.min + b.max);
+			return (Math::abs(d.x) + Math::abs(d.y) + Math::abs(d.z));
+		}
+
+		_FORCE_INLINE_ int select_by_proximity(const Volume &a, const Volume &b) const {
+			return (get_proximity_to(a) < get_proximity_to(b) ? 0 : 1);
+		}
+
+		//
+		_FORCE_INLINE_ bool intersects(const Volume &b) const {
+			return ((min.x <= b.max.x) &&
+					(max.x >= b.min.x) &&
+					(min.y <= b.max.y) &&
+					(max.y >= b.min.y) &&
+					(min.z <= b.max.z) &&
+					(max.z >= b.min.z));
+		}
+	};
+
+	struct Node {
+		Volume volume;
+		Node *parent = nullptr;
+		union {
+			Node *childs[2];
+			void *data;
+		};
+
+		_FORCE_INLINE_ bool is_leaf() const { return data != nullptr; }
+		_FORCE_INLINE_ bool is_internal() const { return (!is_leaf()); }
+
+		_FORCE_INLINE_ int get_index_in_parent() const {
+			ERR_FAIL_COND_V(!parent, 0);
+			return (parent->childs[1] == this) ? 1 : 0;
+		}
+		_FORCE_INLINE_ void get_max_depth(int depth, int &maxdepth) {
+			if (is_internal()) {
+				childs[0]->get_max_depth(depth + 1, maxdepth);
+				childs[1]->get_max_depth(depth + 1, maxdepth);
+			} else {
+				maxdepth = MAX(maxdepth, depth);
+			}
+		}
+
+		//
+		int count_leaves() const {
+			if (is_internal())
+				return childs[0]->count_leaves() + childs[1]->count_leaves();
+			else
+				return (1);
+		}
+
+		bool is_left_of_axis(const Vector3 &org, const Vector3 &axis) const {
+			return axis.dot(volume.get_center() - org) <= 0;
+		}
+
+		Node() {
+			childs[0] = nullptr;
+			childs[1] = nullptr;
+		}
+	};
+
+	// Fields
+	Node *bvh_root = nullptr;
+	int lkhd = -1;
+	int total_leaves = 0;
+	uint32_t opath = 0;
+
+	enum {
+		ALLOCA_STACK_SIZE = 128
+	};
+
+	_FORCE_INLINE_ void _delete_node(Node *p_node);
+	void _recurse_delete_node(Node *p_node);
+	_FORCE_INLINE_ Node *_create_node(Node *p_parent, void *p_data);
+	_FORCE_INLINE_ DynamicBVH::Node *_create_node_with_volume(Node *p_parent, const Volume &p_volume, void *p_data);
+	_FORCE_INLINE_ void _insert_leaf(Node *p_root, Node *p_leaf);
+	_FORCE_INLINE_ Node *_remove_leaf(Node *leaf);
+	void _fetch_leaves(Node *p_root, LocalVector<Node *> &r_leaves, int p_depth = -1);
+	static int _split(Node **leaves, int p_count, const Vector3 &p_org, const Vector3 &p_axis);
+	static Volume _bounds(Node **leaves, int p_count);
+	void _bottom_up(Node **leaves, int p_count);
+	Node *_top_down(Node **leaves, int p_count, int p_bu_threshold);
+	Node *_node_sort(Node *n, Node *&r);
+
+	_FORCE_INLINE_ void _update(Node *leaf, int lookahead = -1);
+
+	void _extract_leaves(Node *p_node, List<ID> *r_elements);
+
+	_FORCE_INLINE_ bool _ray_aabb(const Vector3 &rayFrom, const Vector3 &rayInvDirection, const unsigned int raySign[3], const Vector3 bounds[2], real_t &tmin, real_t lambda_min, real_t lambda_max) {
+		real_t tmax, tymin, tymax, tzmin, tzmax;
+		tmin = (bounds[raySign[0]].x - rayFrom.x) * rayInvDirection.x;
+		tmax = (bounds[1 - raySign[0]].x - rayFrom.x) * rayInvDirection.x;
+		tymin = (bounds[raySign[1]].y - rayFrom.y) * rayInvDirection.y;
+		tymax = (bounds[1 - raySign[1]].y - rayFrom.y) * rayInvDirection.y;
+
+		if ((tmin > tymax) || (tymin > tmax))
+			return false;
+
+		if (tymin > tmin)
+			tmin = tymin;
+
+		if (tymax < tmax)
+			tmax = tymax;
+
+		tzmin = (bounds[raySign[2]].z - rayFrom.z) * rayInvDirection.z;
+		tzmax = (bounds[1 - raySign[2]].z - rayFrom.z) * rayInvDirection.z;
+
+		if ((tmin > tzmax) || (tzmin > tmax))
+			return false;
+		if (tzmin > tmin)
+			tmin = tzmin;
+		if (tzmax < tmax)
+			tmax = tzmax;
+		return ((tmin < lambda_max) && (tmax > lambda_min));
+	}
+
+public:
+	// Methods
+	void clear();
+	bool empty() const { return (0 == bvh_root); }
+	void optimize_bottom_up();
+	void optimize_top_down(int bu_threshold = 128);
+	void optimize_incremental(int passes);
+	ID insert(const AABB &p_box, void *p_userdata);
+	void update(const ID &p_id, const AABB &p_box);
+	void remove(const ID &p_id);
+	void get_elements(List<ID> *r_elements);
+
+	/* Discouraged, but works as a reference on how it must be used */
+	struct DefaultQueryResult {
+		virtual bool operator()(void *p_data) = 0; //return true whether you want to continue the query
+		virtual ~DefaultQueryResult() {}
+	};
+
+	template <class QueryResult>
+	_FORCE_INLINE_ void aabb_query(const AABB &p_aabb, QueryResult &r_result);
+	template <class QueryResult>
+	_FORCE_INLINE_ void ray_query(const Vector3 &p_from, const Vector3 &p_to, QueryResult &r_result);
+
+	DynamicBVH();
+	~DynamicBVH();
+};
+
+template <class QueryResult>
+void DynamicBVH::aabb_query(const AABB &p_box, QueryResult &r_result) {
+	if (!bvh_root) {
+		return;
+	}
+
+	Volume volume;
+	volume.min = p_box.position;
+	volume.max = p_box.position + p_box.size;
+
+	const Node **stack = (const Node **)alloca(ALLOCA_STACK_SIZE * sizeof(const Node *));
+	stack[0] = bvh_root;
+	int32_t depth = 1;
+	int32_t threshold = ALLOCA_STACK_SIZE - 2;
+
+	LocalVector<const Node *> aux_stack; //only used in rare occasions when you run out of alloca memory because tree is too unbalanced. Should correct itself over time.
+
+	do {
+		const Node *n = stack[depth - 1];
+		depth--;
+		if (n->volume.intersects(volume)) {
+			if (n->is_internal()) {
+				if (depth > threshold) {
+					if (aux_stack.empty()) {
+						aux_stack.resize(ALLOCA_STACK_SIZE * 2);
+						copymem(aux_stack.ptr(), stack, ALLOCA_STACK_SIZE * sizeof(const Node *));
+					} else {
+						aux_stack.resize(aux_stack.size() * 2);
+					}
+					stack = aux_stack.ptr();
+					threshold = aux_stack.size() - 2;
+				}
+				stack[depth++] = n->childs[0];
+				stack[depth++] = n->childs[1];
+			} else {
+				if (r_result(n->data)) {
+					return;
+				}
+			}
+		}
+	} while (depth > 0);
+}
+
+template <class QueryResult>
+void DynamicBVH::ray_query(const Vector3 &p_from, const Vector3 &p_to, QueryResult &r_result) {
+	Vector3 ray_dir = (p_to - p_from);
+	ray_dir.normalize();
+
+	///what about division by zero? --> just set rayDirection[i] to INF/B3_LARGE_FLOAT
+	Vector3 inv_dir;
+	inv_dir[0] = ray_dir[0] == real_t(0.0) ? real_t(1e20) : real_t(1.0) / ray_dir[0];
+	inv_dir[1] = ray_dir[1] == real_t(0.0) ? real_t(1e20) : real_t(1.0) / ray_dir[1];
+	inv_dir[2] = ray_dir[2] == real_t(0.0) ? real_t(1e20) : real_t(1.0) / ray_dir[2];
+	unsigned int signs[3] = { inv_dir[0] < 0.0, inv_dir[1] < 0.0, inv_dir[2] < 0.0 };
+
+	real_t lambda_max = ray_dir.dot(p_to - p_from);
+
+	Vector3 bounds[2];
+
+	const Node **stack = (const Node **)alloca(ALLOCA_STACK_SIZE * sizeof(const Node *));
+	stack[0] = bvh_root;
+	int32_t depth = 1;
+	int32_t threshold = ALLOCA_STACK_SIZE - 2;
+
+	LocalVector<const Node *> aux_stack; //only used in rare occasions when you run out of alloca memory because tree is too unbalanced. Should correct itself over time.
+
+	do {
+		const Node *node = stack[--depth];
+		bounds[0] = node->volume.min;
+		bounds[1] = node->volume.max;
+		real_t tmin = 1.f, lambda_min = 0.f;
+		unsigned int result1 = false;
+		result1 = _ray_aabb(p_from, inv_dir, signs, bounds, tmin, lambda_min, lambda_max);
+		if (result1) {
+			if (node->is_internal()) {
+				if (depth > threshold) {
+					if (aux_stack.empty()) {
+						aux_stack.resize(ALLOCA_STACK_SIZE * 2);
+						copymem(aux_stack.ptr(), stack, ALLOCA_STACK_SIZE * sizeof(const Node *));
+					} else {
+						aux_stack.resize(aux_stack.size() * 2);
+					}
+					stack = aux_stack.ptr();
+					threshold = aux_stack.size() - 2;
+				}
+				stack[depth++] = node->childs[0];
+				stack[depth++] = node->childs[1];
+			} else {
+				if (r_result(node->data)) {
+					return;
+				}
+			}
+		}
+	} while (depth > 0);
+}
+
+#endif // DYNAMICBVH_H