Optimize entity-entity collision (#6587)

* Add IrrLicht type aliases
* Add hash for IrrLicht vector
* Add object map

src/server/serveractiveobjectmap.h

@@ -0,0 +1,143 @@
+/*
+Minetest
+Copyright (C) 2018 numZero, Lobachevsky Vitaly <numzer0@yandex.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#pragma once
+#include <unordered_set>
+#include <unordered_map>
+#include <vector>
+#include "irr_v3d.h"
+#include "irr_aabb3d.h"
+
+class ServerActiveObject;
+
+/*!
+ * The class to speed up collision tests.
+ *
+ * @note It stores any objects but only those that has valid collision box
+ * (`physical` Lua entities) are actually processed.
+ * @note It uses world coordinate units, i.e. node size is always BS.
+ */
+struct ServerActiveObjectMap
+{
+	struct Wrapper
+	{
+		ServerActiveObject *object;
+		aabb3s16 box;
+		bool has_box;
+	};
+
+	/*!
+	 * Adds object to the map. It must have valid ID.
+	 *
+	 * If an object with the same ID already exists in the map,
+	 * std::logic_error is thrown.
+	 */
+	void addObject(ServerActiveObject *object);
+
+	/*!
+	 * Removes object from the map. The pointer must be valid.
+	 * See `removeObject(u16)` for details.
+	 */
+	void removeObject(ServerActiveObject *object);
+
+	/*!
+	 * Removes object from the map.
+	 *
+	 * If the object is not found, the call is ignored.
+	 * The function never throws, unless the underlying container throws.
+	 */
+	ServerActiveObject *removeObject(u16 id);
+
+	/*!
+	 * Updates object metadata stored in the map.
+	 * See `updateObject(u16)` for details.
+	 */
+	void updateObject(ServerActiveObject *object);
+
+	/*!
+	 * Updates object metadata stored in the map.
+	 *
+	 * The metadata includes (approximate) absolute collision box and
+	 * its existence (`physical` property for Lua entities).
+	 * This function must be called after each change of these properties,
+	 * including each object movement.
+	 */
+	void updateObject(u16 id);
+
+	/*!
+	 * Returns the object with given ID, if any.
+	 * Returns NULL otherwise.
+	 */
+	ServerActiveObject *getObject(u16 id) const;
+
+	/*!
+	 * Checks if the given ID is free and valid (i.e. non-zero).
+	 */
+	bool isFreeId(u16 id);
+
+	/*!
+	 * Returns a free ID, if any. Returns 0 in the case of failure.
+	 *
+	 * @note This function doesn't reserve the ID; it remains free until
+	 * an object with that ID is added.
+	 * @note This function tries to reclaim freed IDs as late as possible.
+	 * However, there is no guarantee.
+	 */
+	u16 getFreeId();
+
+	/*!
+	 * Returns a list of objects whose base position is at distance less
+	 * than @p radius from @p pos.
+	 *
+	 * @note Due to inexact nature of floating-point computations, it is
+	 * undefined whether an object lying exactly at the boundary is included
+	 * in the list or not.
+	 * @note Objects with base position outside of the collision box may not
+	 * be returned.
+	 * @note Objects without valid collision box are not returned.
+	 */
+	std::vector<u16> getObjectsInsideRadius(v3f pos, float radius);
+
+	/*!
+	 * Returns a list of objects whose collision box intersects with @p box
+	 *
+	 * @note Due to inexact nature of floating-point computations, it is
+	 * undefined whether an object lying exactly at the boundary is included
+	 * in the list or not.
+	 */
+	std::vector<u16> getObjectsTouchingBox(const aabb3f &box);
+
+	/*!
+	 * Returns count of objects in the map.
+	 */
+	std::size_t size() const { return objects.size(); }
+
+	/*!
+	 * Returns reference to the underlying container.
+	 */
+	const std::unordered_map<u16, Wrapper> &getObjects() const { return objects; }
+
+private:
+	void addObjectRefs(u16 id, const aabb3s16 &box);
+	void removeObjectRefs(u16 id, const aabb3s16 &box);
+	std::unordered_set<u16> getObjectsNearBox(const aabb3s16 &box);
+
+	std::unordered_map<u16, Wrapper> objects;
+	std::unordered_multimap<v3s16, u16> refmap;
+};