Moved everything into a C++ GDNative class, and changed it to a floodfill algorithm.

Native/.gitignore

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Native/Heatmap.cpp

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+#include "Heatmap.h"
+#include <TileMap.hpp>
+#include <SceneTree.hpp>
+#include <Viewport.hpp>
+#include <deque>
+#include <TileSet.hpp>
+
+namespace godot {
+	inline float lerp(const float& a, const float& b, const float& t) {
+		return a + t * (b - a);
+	}
+
+	void Heatmap::_register_methods() {
+		//public
+		register_method("_ready", &Heatmap::_ready);
+		register_method("_draw", &Heatmap::_draw);
+		register_method("_process", &Heatmap::_process);
+		register_method("best_direction_for", &Heatmap::best_direction_for);
+		register_method("calculate_point_index", &Heatmap::calculate_point_index);
+		register_method("calculate_point_index_for_world_position", &Heatmap::calculate_point_index_for_world_position);
+
+		//semi-private
+		register_method("_on_Events_player_moved", &Heatmap::on_Events_player_moved);
+
+		//properties
+		register_property<Heatmap, NodePath>("pathfinding_tilemap", &Heatmap::m_pathfinding_tilemap, NodePath());
+		register_property<Heatmap, bool>("draw_debug", &Heatmap::m_draw_debug, false);
+	}
+
+	Heatmap::Heatmap() : m_draw_debug(false), m_grid(nullptr), m_max_heat(0), m_max_heat_cache(0),
+		m_x_max(0), m_y_max(0), m_x_min(0), m_y_min(0), m_updating(false) {
+	}
+
+	Heatmap::~Heatmap() {
+	}
+
+	void Heatmap::_init() {
+	}
+
+	void Heatmap::_ready() {
+		m_grid = (TileMap*)get_node(m_pathfinding_tilemap);
+		if (m_grid == nullptr) {
+			Godot::print_error("No tilemap found for Heatmap node.", __FUNCTION__, __FILE__, __LINE__ - 2);
+			return;
+		}
+
+		m_map_limits = m_grid->get_used_rect();
+		m_x_min = m_map_limits.position.x;
+		m_x_max = m_map_limits.size.x - m_map_limits.position.x;
+		m_y_min = m_map_limits.position.y;
+		m_y_max = m_map_limits.size.y - m_map_limits.position.y;
+
+		unsigned int highest_index = calculate_point_index(m_map_limits.size - m_map_limits.position);
+		m_cells_heat.resize(highest_index);
+		m_cells_heat_cache.resize(highest_index);
+		for (unsigned int i = 0; i < highest_index; ++i) {
+			m_cells_heat[i] = -1;
+		}
+
+		find_all_obstacles();
+
+		get_tree()->get_root()->find_node("Events", true, false)->connect("player_moved", this, "_on_Events_player_moved");
+	}
+
+	//For every cell in 2D array, check the heat and draw a rectangle colored according to its distance from the goal,
+	//get the direction it points to, and draw a simple vector line.
+	void Heatmap::_draw() {
+		if (!m_draw_debug) {
+			return;
+		}
+
+		Rect2 tile;
+		Vector2 cell_size = m_grid->get_cell_size();
+		tile.set_size(cell_size);
+		cell_size /= 2;
+
+		for (int y = int(m_y_min); y<int(m_y_max); ++y) {
+			for (int x = int(m_x_min); x<int(m_x_max); ++x) {
+				Vector2 point = Vector2(float(x), float(y));
+				Vector2 world_position = m_grid->map_to_world(point);
+				tile.set_position(world_position);
+
+				unsigned int cell_index = calculate_point_index(point);
+				int heat = m_cells_heat[cell_index];
+				if (heat == -1) {
+					continue;
+				}
+				float proportion = lerp(0.0f, 1.0f, float(heat) / float(m_max_heat));
+
+				draw_rect(tile, Color(1.0f - proportion, 0, proportion, 0.75f), true);
+
+				world_position += cell_size;
+				Vector2 direction = best_direction_for(point, false);
+				draw_rect(Rect2(world_position.x - 5, world_position.y - 5, 10, 10), Color(0, 1, 0), false);
+				draw_line(world_position, world_position + (direction * 20), Color(1, 1, 1));
+			}
+		}
+	}
+
+	void Heatmap::_process(float delta) {
+		if (!m_updating) {
+			return;
+		}
+
+		//Seeing if future::get is ready to deliver data or if the thread is still crunching numbers.
+		//_Is_Ready is not yet standardized, so we check with as immediate a timeout as we can.
+		if (m_future.wait_for(std::chrono::seconds(0)) == std::future_status::ready) {
+			Vector2 player_cell_position = m_future.get();
+			thread_done(player_cell_position);
+		}
+	}
+
+	//for the 3x3 grid surrounding the cell, find the one with the least heat that isn't -1 (invalid), and return a vector
+	//that points in its direction. Note that there could be multiple tiles with the same heat, which could cause
+	Vector2 Heatmap::best_direction_for(Vector2 t_location, bool t_is_world_location) {
+		Vector2 point = t_is_world_location ? m_grid->world_to_map(t_location) : t_location;
+		Vector2 world_location = t_is_world_location ? t_location : m_grid->map_to_world(point);
+		unsigned int cell_index = calculate_point_index(point);
+
+		if (cell_index < 0 || cell_index >= m_cells_heat.size()) {
+			return (m_last_player_cell_position - world_location).normalized();
+		}
+
+		Vector2 best_neighbor = point;
+		int best_heat = m_cells_heat[cell_index];
+		if (best_heat == -1) {
+			return (m_last_player_cell_position - world_location).normalized();
+		}
+
+		for (int y = 0; y < 3; ++y) {
+			for (int x = 0; x < 3; ++x) {
+				Vector2 point_relative = Vector2(point.x + float(x) - 1.0f, point.y + float(y) - 1.0f);
+
+				if (is_out_of_bounds(point_relative) || std::find(m_obstacles.begin(), m_obstacles.end(), point_relative) != m_obstacles.end()) {
+					continue;
+				}
+
+				unsigned int point_relative_index = calculate_point_index(point_relative);
+				if (point_relative_index == cell_index) {
+					continue;
+				}
+
+				if (point_relative_index >= 0 && point_relative_index < m_cells_heat.size()) {
+					int heat = m_cells_heat[point_relative_index];
+
+					if (heat == -1) {
+						continue;
+					}
+
+					if (heat <= best_heat) {
+						best_heat = heat;
+						best_neighbor = point_relative;
+					}
+				}
+			}
+		}
+
+		Vector2 world_neighbor = m_grid->map_to_world(best_neighbor);
+		Vector2 direction = (world_neighbor - world_location).normalized();
+		if (direction.length_squared() == 0) {
+			return (m_last_player_cell_position - world_location).normalized();
+		}
+		return direction;
+	}
+
+	unsigned int Heatmap::calculate_point_index(Vector2 t_point) {
+		return int((t_point.x - m_map_limits.position.x) + m_map_limits.size.x * (t_point.y - m_map_limits.position.y));
+	}
+
+	unsigned int Heatmap::calculate_point_index_for_world_position(Vector2 t_world_position) {
+		return calculate_point_index(m_grid->world_to_map(t_world_position));
+	}
+
+	//Runs through every cell and checks if the autotile bitmask of that cell covers the entire cell.
+	//If so, it is an obstacle. This does mean that thin corners can seem traversable, even though
+	//they wouldn't be.
+	void Heatmap::find_all_obstacles() {
+		Ref<TileSet> tileset = m_grid->get_tileset();
+		Array tile_ids = tileset->get_tiles_ids();
+
+		//TODO: Account for non-autotile tilesets.
+		for (int y = m_y_min; y < m_y_max; ++y) {
+			for (int x = m_x_min; x < m_x_max; ++x) {
+				int cell_id = m_grid->get_cell(x, y);
+				if (cell_id == -1 || !tile_ids.has(cell_id)) {
+					continue;
+				}
+				int cell_bitmask = tileset->autotile_get_bitmask(cell_id, m_grid->get_cell_autotile_coord(x, y));
+				TileSet::BitmaskMode mode = tileset->autotile_get_bitmask_mode(cell_id);
+
+				int all_covered = 325; //Bitmask is the sum of TileSet::BitmaskMode enum flags.
+				if (mode == TileSet::BITMASK_3X3 || mode == TileSet::BITMASK_3X3_MINIMAL) {
+					all_covered = 495;
+				}
+
+				if (cell_bitmask == all_covered) {
+					m_obstacles.push_back(Vector2(x, y));
+				}
+			}
+		}
+	}
+
+	//Breadth-first search using a queue.
+	Vector2 Heatmap::refresh_cells_heat(Vector2 t_cell_position) {
+		std::deque<HeatCell> queue;
+		//We begin with 4 cells of goals instead of 1 - this alleviates the problem of multiple cells
+		//having the same amount of heat.
+		queue.push_back(HeatCell(Vector2(t_cell_position.x, t_cell_position.y), 0));
+		queue.push_back(HeatCell(Vector2(t_cell_position.x - 1, t_cell_position.y), 0));
+		queue.push_back(HeatCell(Vector2(t_cell_position.x - 1, t_cell_position.y - 1), 0));
+		queue.push_back(HeatCell(Vector2(t_cell_position.x, t_cell_position.y - 1), 0));
+		m_max_heat_cache = 0;
+
+		while (!queue.empty()) {
+			HeatCell cell = queue.front();
+			queue.pop_front();
+
+			Vector2 position = cell.position;
+			int layer = cell.layer;
+
+			unsigned int index = calculate_point_index(position);
+			if (index < 0 || index >= m_cells_heat_cache.size()) {
+				continue;
+			}
+			m_cells_heat_cache[index] = layer;
+			if (layer > m_max_heat_cache) {
+				m_max_heat_cache = layer;
+			}
+
+			for (int y = 0; y < 3; ++y) {
+				for (int x = 0; x < 3; ++x) {
+					Vector2 point = Vector2(position.x + float(x) - 1.0f, position.y + float(y) - 1.0f);
+					unsigned int cell_index = calculate_point_index(point);
+					HeatCell new_cell = HeatCell(point, layer + 1);
+
+					if (   cell_index != index
+						&& cell_index >= 0 && cell_index < m_cells_heat_cache.size()
+						&& m_cells_heat_cache[cell_index] == -1
+						&& !is_out_of_bounds(point)
+						&& std::find(queue.begin(), queue.end(), new_cell) == queue.end()
+						&& std::find(m_obstacles.begin(), m_obstacles.end(), point) == m_obstacles.end()) {
+
+						queue.push_back(new_cell);
+					}
+				}
+			}
+		}
+
+		return t_cell_position;
+	}
+
+	//Copies the cached, thread specific versions that were used into those used by the main thread.
+	void Heatmap::thread_done(Vector2 t_cell_position) {
+		m_updating = false;
+
+		m_max_heat = m_max_heat_cache;
+		for (int i = 0; i < m_cells_heat.size(); ++i) {
+			m_cells_heat[i] = m_cells_heat_cache[i];
+		}
+		m_last_player_cell_position = t_cell_position;
+
+		update();
+	}
+
+	bool Heatmap::is_out_of_bounds(Vector2 t_position) {
+		return t_position.x < m_x_min || t_position.y < m_y_min
+			|| t_position.x > m_x_max || t_position.y > m_y_max;
+	}
+
+	void Heatmap::on_Events_player_moved(Node2D* t_player) {
+		if (m_updating) {
+			return;
+		}
+
+		Vector2 player_cell_position = m_grid->world_to_map(t_player->get_global_position());
+		bool out_of_bounds = is_out_of_bounds(player_cell_position);
+		Vector2 difference = player_cell_position - m_last_player_cell_position;
+
+		if (!out_of_bounds && (difference.x != 0 || difference.y != 0)) {
+			for (int i = 0; i < m_cells_heat_cache.size(); ++i) {
+				m_cells_heat_cache[i] = -1;
+			}
+
+			m_updating = true;
+
+			// Launch an immediate new thread with ::launch::async.
+			// Without that flag, it waits for a future.get()/wait() before starting work.
+			m_future = std::async(std::launch::async, &Heatmap::refresh_cells_heat, this, player_cell_position);
+		}
+	}
+}

Native/Heatmap.h

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+// Heatmap
+// Francois "@Razoric480" Belair
+//
+// GDNative Godot Class that uses a floodfill algorithm. Radiating out from the player position, it covers the whole tilemap.
+// Each step removed adds one to the layer count. This can then be used by agents for quick
+// lookup based pathfinding, instead of calculating A-star paths or other, potentially more expensive pathfinding routines.
+
+#ifndef HEATMAP_H
+#define HEATMAP_H
+
+#include <Godot.hpp>
+#include <Node2D.hpp>
+#include <vector>
+#include <future>
+
+namespace godot {
+	//Forward declarations
+	class TileMap;
+
+	// HeatCell. Simple structure used by the `refresh_cells_heat` member function to contain both
+	// position and current layer in the flood fill search.
+	struct HeatCell {
+		HeatCell(Vector2 t_position, int t_layer) {
+			position = t_position;
+			layer = t_layer;
+		}
+		Vector2 position;
+		int layer;
+
+		bool operator ==(HeatCell const& other) {
+			return other.layer == layer && other.position == position;
+		}
+
+		bool operator !=(HeatCell const& other) {
+			return other.layer != layer || other.position != position;
+		}
+	};
+
+	class Heatmap : public Node2D {
+		GODOT_CLASS(Heatmap, Node2D)
+
+	public:
+		Heatmap();
+		~Heatmap();
+
+		static void _register_methods();
+
+		void _init();
+		void _ready();
+		void _draw();
+		void _process(float delta);
+
+		Vector2 best_direction_for(Vector2 t_location, bool t_is_world_location);
+		unsigned int calculate_point_index(Vector2 t_point);
+		unsigned int calculate_point_index_for_world_position(Vector2 t_world_position);
+
+	private:
+		void find_all_obstacles();
+		Vector2 refresh_cells_heat(Vector2 t_cell_position);
+		bool is_out_of_bounds(Vector2 t_position);
+		void on_Events_player_moved(Node2D* t_player);
+		void thread_done(Vector2 t_cell_position);
+
+	private:
+		NodePath m_pathfinding_tilemap;
+		bool m_draw_debug;
+
+		TileMap* m_grid;
+		Rect2 m_map_limits;
+		float m_x_min;
+		float m_x_max;
+		float m_y_min;
+		float m_y_max;
+		int m_max_heat;
+		int m_max_heat_cache;
+		bool m_updating;
+
+		std::vector<int> m_cells_heat;
+		std::vector<int> m_cells_heat_cache;
+		std::vector<Vector2> m_obstacles;
+		Vector2 m_last_player_cell_position;
+		std::future<Vector2> m_future;
+	};
+}
+
+#endif /* HEATMAP_H */

Native/Heatmap.sln

@@ -0,0 +1,25 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 16
+VisualStudioVersion = 16.0.29230.47
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "Heatmap", "Heatmap.vcxproj", "{95F50422-B0D5-44A4-8A83-3B56BFC6B7B0}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|x64 = Debug|x64
+		Release|x64 = Release|x64
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{95F50422-B0D5-44A4-8A83-3B56BFC6B7B0}.Debug|x64.ActiveCfg = Debug|x64
+		{95F50422-B0D5-44A4-8A83-3B56BFC6B7B0}.Debug|x64.Build.0 = Debug|x64
+		{95F50422-B0D5-44A4-8A83-3B56BFC6B7B0}.Release|x64.ActiveCfg = Release|x64
+		{95F50422-B0D5-44A4-8A83-3B56BFC6B7B0}.Release|x64.Build.0 = Release|x64
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {6B60736E-491D-46DB-B927-593F9A8CEDF2}
+	EndGlobalSection
+EndGlobal

Native/Heatmap.vcxproj

@@ -0,0 +1,110 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <ItemGroup Label="ProjectConfigurations">
+    <ProjectConfiguration Include="Debug|x64">
+      <Configuration>Debug</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|x64">
+      <Configuration>Release</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+  </ItemGroup>
+  <ItemGroup>
+    <ClInclude Include="Heatmap.h" />
+  </ItemGroup>
+  <ItemGroup>
+    <ClCompile Include="gdlibrary.cpp" />
+    <ClCompile Include="Heatmap.cpp" />
+  </ItemGroup>
+  <PropertyGroup Label="Globals">
+    <VCProjectVersion>16.0</VCProjectVersion>
+    <ProjectGuid>{95F50422-B0D5-44A4-8A83-3B56BFC6B7B0}</ProjectGuid>
+    <Keyword>Win32Proj</Keyword>
+    <RootNamespace>Heatmap</RootNamespace>
+    <WindowsTargetPlatformVersion>10.0</WindowsTargetPlatformVersion>
+  </PropertyGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.Default.props" />
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'" Label="Configuration">
+    <ConfigurationType>DynamicLibrary</ConfigurationType>
+    <UseDebugLibraries>true</UseDebugLibraries>
+    <PlatformToolset>v142</PlatformToolset>
+    <CharacterSet>Unicode</CharacterSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'" Label="Configuration">
+    <ConfigurationType>DynamicLibrary</ConfigurationType>
+    <UseDebugLibraries>false</UseDebugLibraries>
+    <PlatformToolset>v142</PlatformToolset>
+    <WholeProgramOptimization>true</WholeProgramOptimization>
+    <CharacterSet>Unicode</CharacterSet>
+  </PropertyGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
+  <ImportGroup Label="ExtensionSettings">
+  </ImportGroup>
+  <ImportGroup Label="Shared">
+  </ImportGroup>
+  <ImportGroup Label="PropertySheets" Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+  </ImportGroup>
+  <ImportGroup Label="PropertySheets" Condition="'$(Configuration)|$(Platform)'=='Release|x64'">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+  </ImportGroup>
+  <PropertyGroup Label="UserMacros" />
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
+    <LinkIncremental>true</LinkIncremental>
+    <IncludePath>E:\Projects\Games\GDQuest\GDNative\godot-cpp\include;E:\Projects\Games\GDQuest\GDNative\godot-cpp\include\core;E:\Projects\Games\GDQuest\GDNative\godot-cpp\include\gen;E:\Projects\Games\GDQuest\GDNative\godot-cpp\godot_headers;$(IncludePath)</IncludePath>
+    <TargetName>libheatmap</TargetName>
+    <LibraryPath>E:\Projects\Games\GDQuest\GDNative\godot-cpp\bin;$(LibraryPath)</LibraryPath>
+    <OutDir>..\game\assets\libraries\win64\</OutDir>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'">
+    <LinkIncremental>false</LinkIncremental>
+    <IncludePath>E:\Projects\Games\GDQuest\GDNative\godot-cpp\include;E:\Projects\Games\GDQuest\GDNative\godot-cpp\include\core;E:\Projects\Games\GDQuest\GDNative\godot-cpp\include\gen;E:\Projects\Games\GDQuest\GDNative\godot-cpp\godot_headers;$(IncludePath)</IncludePath>
+    <LibraryPath>E:\Projects\Games\GDQuest\GDNative\godot-cpp\bin;$(LibraryPath)</LibraryPath>
+    <OutDir>..\game\assets\libraries\win64\</OutDir>
+    <TargetName>libheatmap</TargetName>
+  </PropertyGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
+    <ClCompile>
+      <PrecompiledHeader>NotUsing</PrecompiledHeader>
+      <WarningLevel>Level3</WarningLevel>
+      <Optimization>Disabled</Optimization>
+      <SDLCheck>true</SDLCheck>
+      <PreprocessorDefinitions>_DEBUG;HEATMAP_EXPORTS;_WINDOWS;_USRDLL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <ConformanceMode>true</ConformanceMode>
+      <PrecompiledHeaderFile>
+      </PrecompiledHeaderFile>
+    </ClCompile>
+    <Link>
+      <SubSystem>Console</SubSystem>
+      <GenerateDebugInformation>true</GenerateDebugInformation>
+      <EnableUAC>false</EnableUAC>
+      <AdditionalDependencies>libgodot-cpp.windows.debug.64.lib;%(AdditionalDependencies)</AdditionalDependencies>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'">
+    <ClCompile>
+      <PrecompiledHeader>NotUsing</PrecompiledHeader>
+      <WarningLevel>Level3</WarningLevel>
+      <Optimization>MaxSpeed</Optimization>
+      <FunctionLevelLinking>true</FunctionLevelLinking>
+      <IntrinsicFunctions>true</IntrinsicFunctions>
+      <SDLCheck>true</SDLCheck>
+      <PreprocessorDefinitions>NDEBUG;HEATMAP_EXPORTS;_WINDOWS;_USRDLL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <ConformanceMode>true</ConformanceMode>
+      <PrecompiledHeaderFile>
+      </PrecompiledHeaderFile>
+    </ClCompile>
+    <Link>
+      <SubSystem>Console</SubSystem>
+      <EnableCOMDATFolding>true</EnableCOMDATFolding>
+      <OptimizeReferences>true</OptimizeReferences>
+      <GenerateDebugInformation>true</GenerateDebugInformation>
+      <EnableUAC>false</EnableUAC>
+      <AdditionalDependencies>libgodot-cpp.windows.release.64.lib;%(AdditionalDependencies)</AdditionalDependencies>
+    </Link>
+  </ItemDefinitionGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
+  <ImportGroup Label="ExtensionTargets">
+  </ImportGroup>
+</Project>

Native/Heatmap.vcxproj.filters

@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <ItemGroup>
+    <Filter Include="Source Files">
+      <UniqueIdentifier>{4FC737F1-C7A5-4376-A066-2A32D752A2FF}</UniqueIdentifier>
+      <Extensions>cpp;c;cc;cxx;def;odl;idl;hpj;bat;asm;asmx</Extensions>
+    </Filter>
+    <Filter Include="Header Files">
+      <UniqueIdentifier>{93995380-89BD-4b04-88EB-625FBE52EBFB}</UniqueIdentifier>
+      <Extensions>h;hh;hpp;hxx;hm;inl;inc;ipp;xsd</Extensions>
+    </Filter>
+    <Filter Include="Resource Files">
+      <UniqueIdentifier>{67DA6AB6-F800-4c08-8B7A-83BB121AAD01}</UniqueIdentifier>
+      <Extensions>rc;ico;cur;bmp;dlg;rc2;rct;bin;rgs;gif;jpg;jpeg;jpe;resx;tiff;tif;png;wav;mfcribbon-ms</Extensions>
+    </Filter>
+  </ItemGroup>
+  <ItemGroup>
+    <ClInclude Include="Heatmap.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+  </ItemGroup>
+  <ItemGroup>
+    <ClCompile Include="gdlibrary.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+    <ClCompile Include="Heatmap.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
+  </ItemGroup>
+</Project>

Native/gdlibrary.cpp

@@ -0,0 +1,15 @@
+#include "Heatmap.h"
+
+extern "C" void GDN_EXPORT godot_gdnative_init(godot_gdnative_init_options *o) {
+    godot::Godot::gdnative_init(o);
+}
+
+extern "C" void GDN_EXPORT godot_gdnative_terminate(godot_gdnative_terminate_options *o) {
+    godot::Godot::gdnative_terminate(o);
+}
+
+extern "C" void GDN_EXPORT godot_nativescript_init(void *handle) {
+    godot::Godot::nativescript_init(handle);
+
+    godot::register_class<godot::Heatmap>();
+}

game/assets/libraries/heatmap.gdnlib

@@ -0,0 +1,14 @@
+[general]
+
+singleton=false
+load_once=true
+symbol_prefix="godot_"
+reloadable=true
+
+[entry]
+
+Windows.64="res://assets/libraries/win64/libheatmap.dll"
+
+[dependencies]
+
+Windows.64=[  ]

game/project.godot

@@ -59,6 +59,11 @@ _global_script_classes=[ {
 "language": "GDScript",
 "path": "res://src/Player/FloorDetector.gd"
 }, {
+"base": "SteeringBehavior2D",
+"class": "FollowHeatmapBehavior2D",
+"language": "GDScript",
+"path": "res://src/AI/Steering/Behaviors/Individual/FollowHeatmapBehavior2D.gd"
+}, {
 "base": "Reference",
 "class": "Hit",
 "language": "GDScript",
@@ -140,6 +145,7 @@ _global_script_class_icons={
 "EvadeBehavior2D": "",
 "FleeBehavior2D": "",
 "FloorDetector": "",
+"FollowHeatmapBehavior2D": "",
 "Hit": "",
 "Hook": "res://assets/icons/icon_hook.svg",
 "HookTarget": "",

game/src/AI/Heatmap.gdns

@@ -0,0 +1,8 @@
+[gd_resource type="NativeScript" load_steps=2 format=2]
+
+[ext_resource path="res://assets/libraries/heatmap.gdnlib" type="GDNativeLibrary" id=1]
+
+[resource]
+resource_name = "heatmap"
+class_name = "Heatmap"
+library = ExtResource( 1 )

game/src/AI/Steering/Behaviors/Individual/FollowHeatmapBehavior2D.gd

@@ -0,0 +1,36 @@
+extends SteeringBehavior2D
+class_name FollowHeatmapBehavior2D
+"""
+A 2D steering behavior that expects a heatmap to be somewhere in the scene.
+It uses that to figure out where it should be going - from large values in its cell
+towards smaller values, with 0 being the goal.
+"""
+
+
+var _heatmap #should be able to do `var _heatmap :Heatmap` here because the GDNS file
+#	has `Heatmap` in class_name but it doesn't work and I get type not defined errors.
+#	Bug, or am I being dumb?
+
+var _last_point_index: int = INF
+var _last_velocity: = Vector2(0, 0)
+
+
+func _ready() -> void:
+	_heatmap = get_tree().root.find_node("Heatmap", true, false)
+	assert _heatmap
+
+
+func _calculate_steering_internal(steering: SteeringMotion2D) -> SteeringMotion2D:
+	var actor = get_actor()
+	var point_index: int = _heatmap.calculate_point_index_for_world_position(actor.global_position)
+	if point_index != _last_point_index:
+		_last_point_index = point_index
+		var to_target: Vector2 = _heatmap.best_direction_for(actor.global_position, true)
+		
+		steering.velocity = to_target * controller.max_acceleration
+		_last_velocity = steering.velocity
+	else:
+		steering.velocity = _last_velocity
+		
+	steering.angular_velocity = 0
+	return steering

game/src/AI/SwarmerEnemy.gd

@@ -0,0 +1,16 @@
+extends Node2D
+"""
+Basic controller for a node2D - its behavior checks the heatmap and points
+its directional vector towards the less heat (the 'goal')
+"""
+
+
+onready var behavior: FollowHeatmapBehavior2D = $BehaviorController2D/FollowHeatmapBehavior2D
+
+var _motion: SteeringMotion2D = SteeringMotion2D.new()
+var speed: float = 250
+
+
+func _physics_process(delta: float) -> void:
+	var desired_velocity: = behavior.calculate_steering(_motion)
+	position += _motion.velocity.normalized() * speed * delta

game/src/AI/SwarmerEnemy.tscn

@@ -0,0 +1,23 @@
+[gd_scene load_steps=5 format=2]
+
+[ext_resource path="res://src/AI/SwarmerEnemy.gd" type="Script" id=1]
+[ext_resource path="res://src/Player/Rectangle.gd" type="Script" id=2]
+[ext_resource path="res://src/AI/Steering/BehaviorController2D.gd" type="Script" id=3]
+[ext_resource path="res://src/AI/Steering/Behaviors/Individual/FollowHeatmapBehavior2D.gd" type="Script" id=4]
+
+[node name="SwarmerEnemy" type="Node2D"]
+script = ExtResource( 1 )
+
+[node name="Body" type="Node2D" parent="."]
+script = ExtResource( 2 )
+size = Vector2( 24, 24 )
+outline = Vector2( 6, 6 )
+color_fill = Color( 0.580392, 0.294118, 0.737255, 1 )
+color_outline = Color( 0.27451, 0.12549, 0.807843, 1 )
+
+[node name="BehaviorController2D" type="Node" parent="."]
+script = ExtResource( 3 )
+actor_path = NodePath("..")
+
+[node name="FollowHeatmapBehavior2D" type="Node" parent="BehaviorController2D"]
+script = ExtResource( 4 )

game/src/AI/SwarmerSpawner.gd

@@ -0,0 +1,30 @@
+extends Node2D
+"""
+Spawns a number of swarmer enemies in the scene, who use the heatmap behavior
+to chase the player for economical pathfinding.
+"""
+
+
+export var spawner_count: = 50
+export var spawn_per_frame: = 10
+export var swarmer: PackedScene
+export var spawn_radius: = 200
+export var minimum_speed: float = 200
+export var maximum_speed: float = 300
+
+
+func _ready():
+	randomize()
+	var r_squared: = spawn_radius*spawn_radius
+	
+	for i in range(spawner_count):
+		if i % spawn_per_frame:
+			yield(get_tree(), "idle_frame")
+		var x: = rand_range(-spawn_radius, spawn_radius)
+		var y: = rand_range(-1, 1) * sqrt(r_squared-x*x)
+		
+		var instance: = swarmer.instance()
+		instance.set_name("Swarmer%s"% i)
+		add_child(instance)
+		instance.speed = rand_range(minimum_speed, maximum_speed)
+		instance.global_position = global_position + Vector2(x,y)

game/src/AI/SwarmerSpawner.tscn

@@ -0,0 +1,8 @@
+[gd_scene load_steps=3 format=2]
+
+[ext_resource path="res://src/AI/SwarmerSpawner.gd" type="Script" id=1]
+[ext_resource path="res://src/AI/SwarmerEnemy.tscn" type="PackedScene" id=2]
+
+[node name="SwarmerSpawner" type="Node2D"]
+script = ExtResource( 1 )
+swarmer = ExtResource( 2 )