From 9ea8b58d20274d8e994748b15f8231d88e3b3e99 Mon Sep 17 00:00:00 2001
From: dmwever <56411717+dmwever@users.noreply.github.com>
Date: Tue, 3 Dec 2024 21:47:26 -0600
Subject: [PATCH 1/9] Add dirty flag and integrate

---
 libopenage/pathfinding/CMakeLists.txt  |  1 +
 libopenage/pathfinding/cost_field.cpp  | 22 +++++++--
 libopenage/pathfinding/cost_field.h    | 28 +++++++++--
 libopenage/pathfinding/demo/demo_0.cpp | 20 ++++----
 libopenage/pathfinding/demo/demo_1.cpp | 16 ++++++-
 libopenage/pathfinding/field_cache.cpp | 32 +++++++++++++
 libopenage/pathfinding/field_cache.h   | 66 ++++++++++++++++++++++++++
 libopenage/pathfinding/integrator.cpp  | 64 +++++++++++++++++--------
 libopenage/pathfinding/integrator.h    | 34 ++++---------
 libopenage/pathfinding/path.h          |  5 ++
 libopenage/pathfinding/pathfinder.cpp  |  3 +-
 libopenage/pathfinding/sector.cpp      |  4 ++
 libopenage/pathfinding/sector.h        |  8 ++++
 libopenage/pathfinding/tests.cpp       |  4 +-
 14 files changed, 242 insertions(+), 65 deletions(-)
 create mode 100644 libopenage/pathfinding/field_cache.cpp
 create mode 100644 libopenage/pathfinding/field_cache.h

diff --git a/libopenage/pathfinding/CMakeLists.txt b/libopenage/pathfinding/CMakeLists.txt
index 7f85264d01..33c2844ace 100644
--- a/libopenage/pathfinding/CMakeLists.txt
+++ b/libopenage/pathfinding/CMakeLists.txt
@@ -1,6 +1,7 @@
 add_sources(libopenage
     cost_field.cpp
 	definitions.cpp
+	field_cache.cpp
     flow_field.cpp
 	grid.cpp
 	integration_field.cpp
diff --git a/libopenage/pathfinding/cost_field.cpp b/libopenage/pathfinding/cost_field.cpp
index 3299084548..4ad1318874 100644
--- a/libopenage/pathfinding/cost_field.cpp
+++ b/libopenage/pathfinding/cost_field.cpp
@@ -13,7 +13,8 @@ namespace openage::path {
 
 CostField::CostField(size_t size) :
 	size{size},
-	cells(this->size * this->size, COST_MIN) {
+	cells(this->size * this->size, COST_MIN),
+	changed{time::time_t::min_value()} {
 	log::log(DBG << "Created cost field with size " << this->size << "x" << this->size);
 }
 
@@ -33,29 +34,42 @@ cost_t CostField::get_cost(size_t idx) const {
 	return this->cells.at(idx);
 }
 
-void CostField::set_cost(const coord::tile_delta &pos, cost_t cost) {
+void CostField::set_cost(const coord::tile_delta &pos, cost_t cost, time::time_t &changed) {
 	this->cells[pos.ne + pos.se * this->size] = cost;
+	this->changed = changed;
 }
 
-void CostField::set_cost(size_t x, size_t y, cost_t cost) {
+void CostField::set_cost(size_t x, size_t y, cost_t cost, time::time_t &changed) {
 	this->cells[x + y * this->size] = cost;
+	this->changed = changed;
 }
 
 void CostField::set_cost(size_t idx, cost_t cost) {
 	this->cells[idx] = cost;
+	this->changed = time::TIME_ZERO;
+}
+
+void CostField::set_cost(size_t idx, cost_t cost,time::time_t &changed) {
+	this->cells[idx] = cost;
+	this->changed = changed;
 }
 
 const std::vector<cost_t> &CostField::get_costs() const {
 	return this->cells;
 }
 
-void CostField::set_costs(std::vector<cost_t> &&cells) {
+void CostField::set_costs(std::vector<cost_t> &&cells, time::time_t &changed) {
 	ENSURE(cells.size() == this->cells.size(),
 	       "cells vector has wrong size: " << cells.size()
 	                                       << "; expected: "
 	                                       << this->cells.size());
 
 	this->cells = std::move(cells);
+	this->changed = changed;
+}
+
+bool CostField::is_dirty(time::time_t &time) {
+	return time <= this->changed;
 }
 
 } // namespace openage::path
diff --git a/libopenage/pathfinding/cost_field.h b/libopenage/pathfinding/cost_field.h
index a1fc87b046..99dd16306c 100644
--- a/libopenage/pathfinding/cost_field.h
+++ b/libopenage/pathfinding/cost_field.h
@@ -6,6 +6,7 @@
 #include <vector>
 
 #include "pathfinding/types.h"
+#include "time/time.h"
 
 
 namespace openage {
@@ -64,8 +65,9 @@ class CostField {
 	 *
 	 * @param pos Coordinates of the cell (relative to field origin).
 	 * @param cost Cost to set.
+	 * @param changed Time cost is set.
 	 */
-	void set_cost(const coord::tile_delta &pos, cost_t cost);
+	void set_cost(const coord::tile_delta &pos, cost_t cost, time::time_t &changed);
 
 	/**
 	 * Set the cost at a specified position.
@@ -73,8 +75,9 @@ class CostField {
 	 * @param x X-coordinate of the cell.
 	 * @param y Y-coordinate of the cell.
 	 * @param cost Cost to set.
+	 * @param changed Time cost is set.
 	 */
-	void set_cost(size_t x, size_t y, cost_t cost);
+	void set_cost(size_t x, size_t y, cost_t cost, time::time_t &changed);
 
 	/**
 	 * Set the cost at a specified position.
@@ -84,6 +87,15 @@ class CostField {
 	 */
 	void set_cost(size_t idx, cost_t cost);
 
+	/**
+	 * Set the cost at a specified position.
+	 *
+	 * @param idx Index of the cell.
+	 * @param cost Cost to set.
+	 * @param changed Time cost is set.
+	 */
+	void set_cost(size_t idx, cost_t cost, time::time_t &changed);
+
 	/**
 	 * Get the cost field values.
 	 *
@@ -95,8 +107,16 @@ class CostField {
 	 * Set the cost field values.
 	 *
 	 * @param cells Cost field values.
+	 * @param changed Time cost is set.
 	 */
-	void set_costs(std::vector<cost_t> &&cells);
+	void set_costs(std::vector<cost_t> &&cells, time::time_t &changed);
+
+	/**
+	 * Check if the cost field is dirty at the specified time.
+	 * 
+	 * @param time Specified time to check.
+	 */
+	bool is_dirty(time::time_t &time);
 
 private:
 	/**
@@ -104,6 +124,8 @@ class CostField {
 	 */
 	size_t size;
 
+	time::time_t changed;
+
 	/**
 	 * Cost field values.
 	 */
diff --git a/libopenage/pathfinding/demo/demo_0.cpp b/libopenage/pathfinding/demo/demo_0.cpp
index 483261ebaf..fbe022e8ef 100644
--- a/libopenage/pathfinding/demo/demo_0.cpp
+++ b/libopenage/pathfinding/demo/demo_0.cpp
@@ -33,15 +33,17 @@ void path_demo_0(const util::Path &path) {
 
 	// Cost field with some obstacles
 	auto cost_field = std::make_shared<CostField>(field_length);
-	cost_field->set_cost(coord::tile_delta{0, 0}, COST_IMPASSABLE);
-	cost_field->set_cost(coord::tile_delta{1, 0}, 254);
-	cost_field->set_cost(coord::tile_delta{4, 3}, 128);
-	cost_field->set_cost(coord::tile_delta{5, 3}, 128);
-	cost_field->set_cost(coord::tile_delta{6, 3}, 128);
-	cost_field->set_cost(coord::tile_delta{4, 4}, 128);
-	cost_field->set_cost(coord::tile_delta{5, 4}, 128);
-	cost_field->set_cost(coord::tile_delta{6, 4}, 128);
-	cost_field->set_cost(coord::tile_delta{1, 7}, COST_IMPASSABLE);
+	
+	time::time_t time = time::TIME_ZERO;
+	cost_field->set_cost(coord::tile_delta{0, 0}, COST_IMPASSABLE, time);
+	cost_field->set_cost(coord::tile_delta{1, 0}, 254, time);
+	cost_field->set_cost(coord::tile_delta{4, 3}, 128, time);
+	cost_field->set_cost(coord::tile_delta{5, 3}, 128, time);
+	cost_field->set_cost(coord::tile_delta{6, 3}, 128, time);
+	cost_field->set_cost(coord::tile_delta{4, 4}, 128, time);
+	cost_field->set_cost(coord::tile_delta{5, 4}, 128, time);
+	cost_field->set_cost(coord::tile_delta{6, 4}, 128, time);
+	cost_field->set_cost(coord::tile_delta{1, 7}, COST_IMPASSABLE, time);
 	log::log(INFO << "Created cost field");
 
 	// Create an integration field from the cost field
diff --git a/libopenage/pathfinding/demo/demo_1.cpp b/libopenage/pathfinding/demo/demo_1.cpp
index 1edeba52a1..ecb0e4cb63 100644
--- a/libopenage/pathfinding/demo/demo_1.cpp
+++ b/libopenage/pathfinding/demo/demo_1.cpp
@@ -11,6 +11,8 @@
 #include "pathfinding/portal.h"
 #include "pathfinding/sector.h"
 #include "util/timer.h"
+#include "time/time_loop.h"
+#include "time/clock.h"
 
 #include "renderer/gui/integration/public/gui_application_with_logger.h"
 #include "renderer/opengl/window.h"
@@ -25,13 +27,17 @@
 namespace openage::path::tests {
 
 void path_demo_1(const util::Path &path) {
+	auto time_loop = std::make_shared<time::TimeLoop>();
+	time_loop->run();
+	auto clock = time_loop->get_clock();
 	auto grid = std::make_shared<Grid>(0, util::Vector2s{4, 3}, 10);
 
+	time::time_t time = clock->get_time();
 	// Initialize the cost field for each sector.
 	for (auto &sector : grid->get_sectors()) {
 		auto cost_field = sector->get_cost_field();
 		std::vector<cost_t> sector_cost = sectors_cost.at(sector->get_id());
-		cost_field->set_costs(std::move(sector_cost));
+		cost_field->set_costs(std::move(sector_cost), time);
 	}
 
 	// Initialize portals between sectors.
@@ -87,16 +93,20 @@ void path_demo_1(const util::Path &path) {
 	coord::tile start{2, 26};
 	coord::tile target{36, 2};
 
+	time::time_t request_time = clock->get_time();
+
 	PathRequest path_request{
 		grid->get_id(),
 		start,
 		target,
+		request_time
 	};
+
+	log::log(INFO << "Pathfinding request at " << request_time);
 	grid->init_portal_nodes();
 	timer.start();
 	Path path_result = pathfinder->get_path(path_request);
 	timer.stop();
-
 	log::log(INFO << "Pathfinding took " << timer.getval() / 1000 << " us");
 
 	// Create a renderer to display the grid and path
@@ -127,6 +137,7 @@ void path_demo_1(const util::Path &path) {
 					grid->get_id(),
 					start,
 					target,
+					clock->get_time()
 				};
 
 				timer.reset();
@@ -147,6 +158,7 @@ void path_demo_1(const util::Path &path) {
 					grid->get_id(),
 					start,
 					target,
+					clock->get_time()
 				};
 
 				timer.reset();
diff --git a/libopenage/pathfinding/field_cache.cpp b/libopenage/pathfinding/field_cache.cpp
new file mode 100644
index 0000000000..9d144e1cc4
--- /dev/null
+++ b/libopenage/pathfinding/field_cache.cpp
@@ -0,0 +1,32 @@
+// Copyright 2024-2024 the openage authors. See copying.md for legal info.
+
+#include "field_cache.h"
+
+namespace openage::path {
+
+void FieldCache::add(std::pair<unsigned long long, unsigned long long> cache_key,
+            std::shared_ptr<IntegrationField> &integration_field,
+            std::shared_ptr<FlowField> &flow_field) {
+    this->cache[cache_key] = std::make_pair(integration_field, flow_field);
+}
+
+void FieldCache::evict(std::pair<unsigned long long, unsigned long long> cache_key) {
+    this->cache.erase(cache_key);
+}
+
+bool FieldCache::is_cached(std::pair<unsigned long long, unsigned long long> cache_key) {
+    auto cached = this->cache.find(cache_key);
+    return cached != this->cache.end();
+}
+
+std::shared_ptr<IntegrationField> FieldCache::get_integration_field(std::pair<unsigned long long, unsigned long long> cache_key) {
+    auto cached = this->cache.find(cache_key);
+    return cached->second.first;
+}
+
+std::shared_ptr<FlowField> FieldCache::get_flow_field(std::pair<unsigned long long, unsigned long long> cache_key) {
+    auto cached = this->cache.find(cache_key);
+    return cached->second.second;
+}
+
+} // namespace openage::path
\ No newline at end of file
diff --git a/libopenage/pathfinding/field_cache.h b/libopenage/pathfinding/field_cache.h
new file mode 100644
index 0000000000..7b98c4d957
--- /dev/null
+++ b/libopenage/pathfinding/field_cache.h
@@ -0,0 +1,66 @@
+// Copyright 2024-2024 the openage authors. See copying.md for legal info.
+
+#pragma once
+
+#include <memory>
+#include <unordered_map>
+
+#include "pathfinding/types.h"
+#include "util/hash.h"
+
+namespace openage {
+namespace coord {
+struct tile_delta;
+} // namespace coord
+
+namespace path {
+class IntegrationField;
+class FlowField;
+
+class FieldCache
+{
+public:
+    FieldCache() = default;
+    ~FieldCache() = default;
+
+    void add(std::pair<unsigned long long, unsigned long long> cache_key,
+             std::shared_ptr<IntegrationField> &integration_field,
+             std::shared_ptr<FlowField> &flow_field);
+
+	void evict(std::pair<unsigned long long, unsigned long long> cache_key);
+
+    bool is_cached(std::pair<unsigned long long, unsigned long long> cache_key);
+
+    std::shared_ptr<IntegrationField> get_integration_field(std::pair<unsigned long long, unsigned long long> cache_key);
+    
+    std::shared_ptr<FlowField> get_flow_field(std::pair<unsigned long long, unsigned long long> cache_key);
+    
+    using get_return_t = std::pair<std::shared_ptr<IntegrationField>, std::shared_ptr<FlowField>>;
+
+private:
+	/**
+	 * Hash function for the field cache.
+	 */
+	struct pair_hash {
+		template <class T1, class T2>
+		std::size_t operator()(const std::pair<T1, T2> &pair) const {
+			return util::hash_combine(std::hash<T1>{}(pair.first), std::hash<T2>{}(pair.second));
+		}
+	};
+
+	/**
+	 * Cache for already computed fields.
+	 *
+	 * Key is the portal ID and the sector ID from which the field was entered. Fields that are cached are
+	 * cleared of dynamic flags, i.e. wavefront or LOS flags. These have to be recalculated
+	 * when the field is reused.
+	 */
+
+	std::unordered_map<std::pair<portal_id_t, sector_id_t>,
+	                   get_return_t,
+	                   pair_hash>
+		cache;
+};
+
+} // namespace path
+} // namespace openage
\ No newline at end of file
diff --git a/libopenage/pathfinding/integrator.cpp b/libopenage/pathfinding/integrator.cpp
index 265c5285cc..d91ac9ecb7 100644
--- a/libopenage/pathfinding/integrator.cpp
+++ b/libopenage/pathfinding/integrator.cpp
@@ -8,6 +8,7 @@
 #include "pathfinding/flow_field.h"
 #include "pathfinding/integration_field.h"
 #include "pathfinding/portal.h"
+#include "pathfinding/field_cache.h"
 
 
 namespace openage::path {
@@ -36,24 +37,32 @@ std::shared_ptr<IntegrationField> Integrator::integrate(const std::shared_ptr<Co
                                                         sector_id_t other_sector_id,
                                                         const std::shared_ptr<Portal> &portal,
                                                         const coord::tile_delta &target,
-                                                        bool with_los) {
+                                                        bool with_los,
+											 			bool evict_cache) {
 	auto cache_key = std::make_pair(portal->get_id(), other_sector_id);
-	auto cached = this->field_cache.find(cache_key);
-	if (cached != this->field_cache.end()) {
+	if (evict_cache) {
+		this->field_cache->evict(cache_key);
+	}
+	if (this->field_cache->is_cached(cache_key)) {
 		log::log(DBG << "Using cached integration field for portal " << portal->get_id()
 		             << " from sector " << other_sector_id);
+					 
+
+		//retrieve cached integration field
+		auto cached_integration_field = this->field_cache->get_integration_field(cache_key);
+
 		if (with_los) {
 			log::log(SPAM << "Performing LOS pass on cached field");
 
 			// Make a copy of the cached field to avoid modifying the cached field
-			auto integration_field = std::make_shared<IntegrationField>(*cached->second.first);
+			auto integration_field = std::make_shared<IntegrationField>(*cached_integration_field);
 
 			// Only integrate LOS; leave the rest of the field as is
 			integration_field->integrate_los(cost_field, other, other_sector_id, portal, target);
 
 			return integration_field;
 		}
-		return cached->second.first;
+		return cached_integration_field;
 	}
 
 	log::log(DBG << "Integrating cost field for portal " << portal->get_id()
@@ -97,17 +106,24 @@ std::shared_ptr<FlowField> Integrator::build(const std::shared_ptr<IntegrationFi
                                              const std::shared_ptr<IntegrationField> &other,
                                              sector_id_t other_sector_id,
                                              const std::shared_ptr<Portal> &portal,
-                                             bool with_los) {
+                                             bool with_los,
+											 bool evict_cache) {
 	auto cache_key = std::make_pair(portal->get_id(), other_sector_id);
-	auto cached = this->field_cache.find(cache_key);
-	if (cached != this->field_cache.end()) {
+	if (evict_cache) {
+		this->field_cache->evict(cache_key);
+	}
+	if (this->field_cache->is_cached(cache_key)) {
 		log::log(DBG << "Using cached flow field for portal " << portal->get_id()
 		             << " from sector " << other_sector_id);
+
+		//retrieve cached flow field
+		auto cached_flow_field = this->field_cache->get_flow_field(cache_key);
+
 		if (with_los) {
 			log::log(SPAM << "Transferring LOS flags to cached flow field");
 
 			// Make a copy of the cached flow field
-			auto flow_field = std::make_shared<FlowField>(*cached->second.second);
+			auto flow_field = std::make_shared<FlowField>(*cached_flow_field);
 
 			// Transfer the LOS flags to the flow field
 			flow_field->transfer_dynamic_flags(integration_field);
@@ -115,7 +131,7 @@ std::shared_ptr<FlowField> Integrator::build(const std::shared_ptr<IntegrationFi
 			return flow_field;
 		}
 
-		return cached->second.second;
+		return cached_flow_field;
 	}
 
 	log::log(DBG << "Building flow field for portal " << portal->get_id()
@@ -140,17 +156,27 @@ Integrator::get_return_t Integrator::get(const std::shared_ptr<CostField> &cost_
                                          sector_id_t other_sector_id,
                                          const std::shared_ptr<Portal> &portal,
                                          const coord::tile_delta &target,
-                                         bool with_los) {
+                                         bool with_los,
+										 bool evict_cache) {
 	auto cache_key = std::make_pair(portal->get_id(), other_sector_id);
-	auto cached = this->field_cache.find(cache_key);
-	if (cached != this->field_cache.end()) {
+	if (evict_cache) {
+		this->field_cache->evict(cache_key);
+	}
+	if (this->field_cache->is_cached(cache_key)) {
 		log::log(DBG << "Using cached integration and flow fields for portal " << portal->get_id()
 		             << " from sector " << other_sector_id);
+
+		
+		//retrieve cached fields
+		auto cached_integration_field = this->field_cache->get_integration_field(cache_key);
+		auto cached_flow_field = this->field_cache->get_flow_field(cache_key);
+
+
 		if (with_los) {
 			log::log(SPAM << "Performing LOS pass on cached field");
 
 			// Make a copy of the cached integration field
-			auto integration_field = std::make_shared<IntegrationField>(*cached->second.first);
+			auto integration_field = std::make_shared<IntegrationField>(*cached_integration_field);
 
 			// Only integrate LOS; leave the rest of the field as is
 			integration_field->integrate_los(cost_field, other, other_sector_id, portal, target);
@@ -158,7 +184,7 @@ Integrator::get_return_t Integrator::get(const std::shared_ptr<CostField> &cost_
 			log::log(SPAM << "Transferring LOS flags to cached flow field");
 
 			// Make a copy of the cached flow field
-			auto flow_field = std::make_shared<FlowField>(*cached->second.second);
+			auto flow_field = std::make_shared<FlowField>(*cached_flow_field);
 
 			// Transfer the LOS flags to the flow field
 			flow_field->transfer_dynamic_flags(integration_field);
@@ -166,11 +192,11 @@ Integrator::get_return_t Integrator::get(const std::shared_ptr<CostField> &cost_
 			return std::make_pair(integration_field, flow_field);
 		}
 
-		return cached->second;
+		return std::make_pair(cached_integration_field, cached_flow_field);
 	}
 
-	auto integration_field = this->integrate(cost_field, other, other_sector_id, portal, target, with_los);
-	auto flow_field = this->build(integration_field, other, other_sector_id, portal);
+	auto integration_field = this->integrate(cost_field, other, other_sector_id, portal, target, with_los, evict_cache);
+	auto flow_field = this->build(integration_field, other, other_sector_id, portal, evict_cache);
 
 	log::log(DBG << "Caching integration and flow fields for portal ID: " << portal->get_id()
 	             << ", sector ID: " << other_sector_id);
@@ -182,7 +208,7 @@ Integrator::get_return_t Integrator::get(const std::shared_ptr<CostField> &cost_
 	std::shared_ptr<FlowField> cached_flow_field = std::make_shared<FlowField>(*flow_field);
 	cached_flow_field->reset_dynamic_flags();
 
-	this->field_cache[cache_key] = std::make_pair(cached_integration_field, cached_flow_field);
+	this->field_cache->add(cache_key, cached_integration_field, cached_flow_field);
 
 	return std::make_pair(integration_field, flow_field);
 }
diff --git a/libopenage/pathfinding/integrator.h b/libopenage/pathfinding/integrator.h
index c27d3c1eb1..690c525ad7 100644
--- a/libopenage/pathfinding/integrator.h
+++ b/libopenage/pathfinding/integrator.h
@@ -2,9 +2,7 @@
 
 #pragma once
 
-#include <cstddef>
 #include <memory>
-#include <unordered_map>
 
 #include "pathfinding/types.h"
 #include "util/hash.h"
@@ -20,6 +18,7 @@ class CostField;
 class FlowField;
 class IntegrationField;
 class Portal;
+class FieldCache;
 
 /**
  * Integrator for the flow field pathfinding algorithm.
@@ -65,7 +64,8 @@ class Integrator {
 	                                            sector_id_t other_sector_id,
 	                                            const std::shared_ptr<Portal> &portal,
 	                                            const coord::tile_delta &target,
-	                                            bool with_los = true);
+	                                            bool with_los = true,
+												bool evict_cache = false);
 
 	/**
 	 * Build the flow field from an integration field.
@@ -91,7 +91,8 @@ class Integrator {
 	                                 const std::shared_ptr<IntegrationField> &other,
 	                                 sector_id_t other_sector_id,
 	                                 const std::shared_ptr<Portal> &portal,
-	                                 bool with_los = true);
+	                                 bool with_los = true,
+					 				 bool evict_cache = false);
 
 	using get_return_t = std::pair<std::shared_ptr<IntegrationField>, std::shared_ptr<FlowField>>;
 
@@ -123,30 +124,11 @@ class Integrator {
 	                 sector_id_t other_sector_id,
 	                 const std::shared_ptr<Portal> &portal,
 	                 const coord::tile_delta &target,
-	                 bool with_los = true);
+	                 bool with_los = true,
+					 bool evict_cache = false);
 
 private:
-	/**
-	 * Hash function for the field cache.
-	 */
-	struct pair_hash {
-		template <class T1, class T2>
-		std::size_t operator()(const std::pair<T1, T2> &pair) const {
-			return util::hash_combine(std::hash<T1>{}(pair.first), std::hash<T2>{}(pair.second));
-		}
-	};
-
-	/**
-	 * Cache for already computed fields.
-	 *
-	 * Key is the portal ID and the sector ID from which the field was entered. Fields that are cached are
-	 * cleared of dynamic flags, i.e. wavefront or LOS flags. These have to be recalculated
-	 * when the field is reused.
-	 */
-	std::unordered_map<std::pair<portal_id_t, sector_id_t>,
-	                   get_return_t,
-	                   pair_hash>
-		field_cache;
+	std::shared_ptr<FieldCache> field_cache;
 };
 
 } // namespace path
diff --git a/libopenage/pathfinding/path.h b/libopenage/pathfinding/path.h
index d1c61ac325..cfeb7bc503 100644
--- a/libopenage/pathfinding/path.h
+++ b/libopenage/pathfinding/path.h
@@ -6,6 +6,7 @@
 
 #include "coord/tile.h"
 #include "pathfinding/types.h"
+#include "time/time.h"
 
 
 namespace openage::path {
@@ -20,6 +21,8 @@ struct PathRequest {
 	coord::tile start;
 	/// Target position of the path.
 	coord::tile target;
+	/// Time request was made.
+	time::time_t time;
 };
 
 /**
@@ -34,6 +37,8 @@ struct Path {
 	/// First waypoint is the start position of the path request.
 	/// Last waypoint is the target position of the path request.
 	std::vector<coord::tile> waypoints;
+	/// Time path was created.
+	time::time_t time;
 };
 
 } // namespace openage::path
diff --git a/libopenage/pathfinding/pathfinder.cpp b/libopenage/pathfinding/pathfinder.cpp
index e46919e62b..0740da3b82 100644
--- a/libopenage/pathfinding/pathfinder.cpp
+++ b/libopenage/pathfinding/pathfinder.cpp
@@ -155,7 +155,8 @@ const Path Pathfinder::get_path(const PathRequest &request) {
 		                                      prev_sector_id,
 		                                      portal,
 		                                      target_delta,
-		                                      with_los);
+		                                      with_los,
+											  next_sector->is_dirty(request.time));
 		flow_fields.push_back(std::make_pair(next_sector_id, sector_fields.second));
 
 		prev_integration_field = sector_fields.first;
diff --git a/libopenage/pathfinding/sector.cpp b/libopenage/pathfinding/sector.cpp
index f50dc209bf..08843fe016 100644
--- a/libopenage/pathfinding/sector.cpp
+++ b/libopenage/pathfinding/sector.cpp
@@ -249,4 +249,8 @@ void Sector::connect_exits() {
 	}
 }
 
+bool Sector::is_dirty(time::time_t time) {
+	return this->cost_field->is_dirty(time);
+}
+
 } // namespace openage::path
diff --git a/libopenage/pathfinding/sector.h b/libopenage/pathfinding/sector.h
index a4ba94fa52..cc2950f25e 100644
--- a/libopenage/pathfinding/sector.h
+++ b/libopenage/pathfinding/sector.h
@@ -9,6 +9,7 @@
 #include "coord/chunk.h"
 #include "pathfinding/portal.h"
 #include "pathfinding/types.h"
+#include "time/time.h"
 
 
 namespace openage::path {
@@ -103,6 +104,13 @@ class Sector {
 	 */
 	void connect_exits();
 
+	/**
+	 * Check if the cost field is dirty at the specified time.
+	 * 
+	 * @param time Specified time to check.
+	 */
+	bool is_dirty(time::time_t time);
+
 private:
 	/**
 	 * ID of the sector.
diff --git a/libopenage/pathfinding/tests.cpp b/libopenage/pathfinding/tests.cpp
index 5f92496ff8..6ec26b392d 100644
--- a/libopenage/pathfinding/tests.cpp
+++ b/libopenage/pathfinding/tests.cpp
@@ -10,6 +10,7 @@
 #include "pathfinding/integration_field.h"
 #include "pathfinding/integrator.h"
 #include "pathfinding/types.h"
+#include "time/time.h"
 
 
 namespace openage {
@@ -23,7 +24,8 @@ void flow_field() {
 	// | 1 | 1 | 1 |
 	// | 1 | X | 1 |
 	// | 1 | 1 | 1 |
-	cost_field->set_costs({1, 1, 1, 1, 255, 1, 1, 1, 1});
+	time::time_t time = time::TIME_ZERO;
+	cost_field->set_costs({1, 1, 1, 1, 255, 1, 1, 1, 1}, time);
 
 	// Test the different field types
 	{

From a12b347421fae83cfc1e73a682929cc72ec6117b Mon Sep 17 00:00:00 2001
From: dmwever <56411717+dmwever@users.noreply.github.com>
Date: Thu, 5 Dec 2024 19:50:20 -0600
Subject: [PATCH 2/9] Update libopenage/pathfinding/cost_field.cpp

Co-authored-by: Christoph Heine <6852422+heinezen@users.noreply.github.com>
---
 libopenage/pathfinding/cost_field.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libopenage/pathfinding/cost_field.cpp b/libopenage/pathfinding/cost_field.cpp
index 4ad1318874..d4ae7f8464 100644
--- a/libopenage/pathfinding/cost_field.cpp
+++ b/libopenage/pathfinding/cost_field.cpp
@@ -14,7 +14,7 @@ namespace openage::path {
 CostField::CostField(size_t size) :
 	size{size},
 	cells(this->size * this->size, COST_MIN),
-	changed{time::time_t::min_value()} {
+	changed{time::TIME_MIN} {
 	log::log(DBG << "Created cost field with size " << this->size << "x" << this->size);
 }
 

From 73647d460ecb5b467c5d081ea4ea44c5f317fe3d Mon Sep 17 00:00:00 2001
From: dmwever <56411717+dmwever@users.noreply.github.com>
Date: Thu, 5 Dec 2024 20:26:51 -0600
Subject: [PATCH 3/9] Add const to time_t and improve docstrings

---
 libopenage/pathfinding/cost_field.cpp  | 10 +++++-----
 libopenage/pathfinding/cost_field.h    | 25 ++++++++++++++-----------
 libopenage/pathfinding/demo/demo_0.cpp |  2 +-
 libopenage/pathfinding/demo/demo_1.cpp |  6 +++---
 libopenage/pathfinding/field_cache.cpp |  2 +-
 libopenage/pathfinding/field_cache.h   |  2 +-
 libopenage/pathfinding/path.h          |  4 ++--
 libopenage/pathfinding/sector.cpp      |  2 +-
 libopenage/pathfinding/sector.h        |  2 +-
 libopenage/pathfinding/tests.cpp       |  2 +-
 10 files changed, 30 insertions(+), 27 deletions(-)

diff --git a/libopenage/pathfinding/cost_field.cpp b/libopenage/pathfinding/cost_field.cpp
index d4ae7f8464..c211d169c1 100644
--- a/libopenage/pathfinding/cost_field.cpp
+++ b/libopenage/pathfinding/cost_field.cpp
@@ -34,12 +34,12 @@ cost_t CostField::get_cost(size_t idx) const {
 	return this->cells.at(idx);
 }
 
-void CostField::set_cost(const coord::tile_delta &pos, cost_t cost, time::time_t &changed) {
+void CostField::set_cost(const coord::tile_delta &pos, cost_t cost, const time::time_t &changed) {
 	this->cells[pos.ne + pos.se * this->size] = cost;
 	this->changed = changed;
 }
 
-void CostField::set_cost(size_t x, size_t y, cost_t cost, time::time_t &changed) {
+void CostField::set_cost(size_t x, size_t y, cost_t cost, const time::time_t &changed) {
 	this->cells[x + y * this->size] = cost;
 	this->changed = changed;
 }
@@ -49,7 +49,7 @@ void CostField::set_cost(size_t idx, cost_t cost) {
 	this->changed = time::TIME_ZERO;
 }
 
-void CostField::set_cost(size_t idx, cost_t cost,time::time_t &changed) {
+void CostField::set_cost(size_t idx, cost_t cost, const time::time_t &changed) {
 	this->cells[idx] = cost;
 	this->changed = changed;
 }
@@ -58,7 +58,7 @@ const std::vector<cost_t> &CostField::get_costs() const {
 	return this->cells;
 }
 
-void CostField::set_costs(std::vector<cost_t> &&cells, time::time_t &changed) {
+void CostField::set_costs(std::vector<cost_t> &&cells, const time::time_t &changed) {
 	ENSURE(cells.size() == this->cells.size(),
 	       "cells vector has wrong size: " << cells.size()
 	                                       << "; expected: "
@@ -68,7 +68,7 @@ void CostField::set_costs(std::vector<cost_t> &&cells, time::time_t &changed) {
 	this->changed = changed;
 }
 
-bool CostField::is_dirty(time::time_t &time) {
+bool CostField::is_dirty(const time::time_t &time) {
 	return time <= this->changed;
 }
 
diff --git a/libopenage/pathfinding/cost_field.h b/libopenage/pathfinding/cost_field.h
index 99dd16306c..e62496acf1 100644
--- a/libopenage/pathfinding/cost_field.h
+++ b/libopenage/pathfinding/cost_field.h
@@ -65,9 +65,9 @@ class CostField {
 	 *
 	 * @param pos Coordinates of the cell (relative to field origin).
 	 * @param cost Cost to set.
-	 * @param changed Time cost is set.
+	 * @param changed Time at which the cost value is changed.
 	 */
-	void set_cost(const coord::tile_delta &pos, cost_t cost, time::time_t &changed);
+	void set_cost(const coord::tile_delta &pos, cost_t cost, const time::time_t &changed);
 
 	/**
 	 * Set the cost at a specified position.
@@ -75,9 +75,9 @@ class CostField {
 	 * @param x X-coordinate of the cell.
 	 * @param y Y-coordinate of the cell.
 	 * @param cost Cost to set.
-	 * @param changed Time cost is set.
+	 * @param changed Time at which the cost value is changed.
 	 */
-	void set_cost(size_t x, size_t y, cost_t cost, time::time_t &changed);
+	void set_cost(size_t x, size_t y, cost_t cost, const time::time_t &changed);
 
 	/**
 	 * Set the cost at a specified position.
@@ -92,9 +92,9 @@ class CostField {
 	 *
 	 * @param idx Index of the cell.
 	 * @param cost Cost to set.
-	 * @param changed Time cost is set.
+	 * @param changed Time at which the cost value is changed.
 	 */
-	void set_cost(size_t idx, cost_t cost, time::time_t &changed);
+	void set_cost(size_t idx, cost_t cost, const time::time_t &changed);
 
 	/**
 	 * Get the cost field values.
@@ -107,16 +107,16 @@ class CostField {
 	 * Set the cost field values.
 	 *
 	 * @param cells Cost field values.
-	 * @param changed Time cost is set.
+	 * @param changed Time at which the cost value is changed.
 	 */
-	void set_costs(std::vector<cost_t> &&cells, time::time_t &changed);
+	void set_costs(std::vector<cost_t> &&cells, const time::time_t &changed);
 
 	/**
 	 * Check if the cost field is dirty at the specified time.
 	 * 
-	 * @param time Specified time to check.
+	 * @param time Cost field is dirty if the cost field is accessed before the latest change to the cost field.
 	 */
-	bool is_dirty(time::time_t &time);
+	bool is_dirty(const time::time_t &time);
 
 private:
 	/**
@@ -124,7 +124,10 @@ class CostField {
 	 */
 	size_t size;
 
-	time::time_t changed;
+	/**
+	 * Time the cost field was last changed.
+	 */
+	const time::time_t changed;
 
 	/**
 	 * Cost field values.
diff --git a/libopenage/pathfinding/demo/demo_0.cpp b/libopenage/pathfinding/demo/demo_0.cpp
index fbe022e8ef..2dfb825fa0 100644
--- a/libopenage/pathfinding/demo/demo_0.cpp
+++ b/libopenage/pathfinding/demo/demo_0.cpp
@@ -34,7 +34,7 @@ void path_demo_0(const util::Path &path) {
 	// Cost field with some obstacles
 	auto cost_field = std::make_shared<CostField>(field_length);
 	
-	time::time_t time = time::TIME_ZERO;
+	const time::time_t time = time::TIME_ZERO;
 	cost_field->set_cost(coord::tile_delta{0, 0}, COST_IMPASSABLE, time);
 	cost_field->set_cost(coord::tile_delta{1, 0}, 254, time);
 	cost_field->set_cost(coord::tile_delta{4, 3}, 128, time);
diff --git a/libopenage/pathfinding/demo/demo_1.cpp b/libopenage/pathfinding/demo/demo_1.cpp
index ecb0e4cb63..a31b9b786b 100644
--- a/libopenage/pathfinding/demo/demo_1.cpp
+++ b/libopenage/pathfinding/demo/demo_1.cpp
@@ -32,7 +32,7 @@ void path_demo_1(const util::Path &path) {
 	auto clock = time_loop->get_clock();
 	auto grid = std::make_shared<Grid>(0, util::Vector2s{4, 3}, 10);
 
-	time::time_t time = clock->get_time();
+	const time::time_t time = clock->get_time();
 	// Initialize the cost field for each sector.
 	for (auto &sector : grid->get_sectors()) {
 		auto cost_field = sector->get_cost_field();
@@ -93,7 +93,7 @@ void path_demo_1(const util::Path &path) {
 	coord::tile start{2, 26};
 	coord::tile target{36, 2};
 
-	time::time_t request_time = clock->get_time();
+	const time::time_t request_time = clock->get_time();
 
 	PathRequest path_request{
 		grid->get_id(),
@@ -102,11 +102,11 @@ void path_demo_1(const util::Path &path) {
 		request_time
 	};
 
-	log::log(INFO << "Pathfinding request at " << request_time);
 	grid->init_portal_nodes();
 	timer.start();
 	Path path_result = pathfinder->get_path(path_request);
 	timer.stop();
+	log::log(INFO << "Pathfinding request at " << request_time);
 	log::log(INFO << "Pathfinding took " << timer.getval() / 1000 << " us");
 
 	// Create a renderer to display the grid and path
diff --git a/libopenage/pathfinding/field_cache.cpp b/libopenage/pathfinding/field_cache.cpp
index 9d144e1cc4..a798e9fbd7 100644
--- a/libopenage/pathfinding/field_cache.cpp
+++ b/libopenage/pathfinding/field_cache.cpp
@@ -29,4 +29,4 @@ std::shared_ptr<FlowField> FieldCache::get_flow_field(std::pair<unsigned long lo
     return cached->second.second;
 }
 
-} // namespace openage::path
\ No newline at end of file
+} // namespace openage::path
diff --git a/libopenage/pathfinding/field_cache.h b/libopenage/pathfinding/field_cache.h
index 7b98c4d957..a1f43a563e 100644
--- a/libopenage/pathfinding/field_cache.h
+++ b/libopenage/pathfinding/field_cache.h
@@ -63,4 +63,4 @@ class FieldCache
 };
 
 } // namespace path
-} // namespace openage
\ No newline at end of file
+} // namespace openage
diff --git a/libopenage/pathfinding/path.h b/libopenage/pathfinding/path.h
index cfeb7bc503..ca6391bf67 100644
--- a/libopenage/pathfinding/path.h
+++ b/libopenage/pathfinding/path.h
@@ -22,7 +22,7 @@ struct PathRequest {
 	/// Target position of the path.
 	coord::tile target;
 	/// Time request was made.
-	time::time_t time;
+	const time::time_t time;
 };
 
 /**
@@ -38,7 +38,7 @@ struct Path {
 	/// Last waypoint is the target position of the path request.
 	std::vector<coord::tile> waypoints;
 	/// Time path was created.
-	time::time_t time;
+	const time::time_t time;
 };
 
 } // namespace openage::path
diff --git a/libopenage/pathfinding/sector.cpp b/libopenage/pathfinding/sector.cpp
index 08843fe016..4556fd42c3 100644
--- a/libopenage/pathfinding/sector.cpp
+++ b/libopenage/pathfinding/sector.cpp
@@ -249,7 +249,7 @@ void Sector::connect_exits() {
 	}
 }
 
-bool Sector::is_dirty(time::time_t time) {
+bool Sector::is_dirty(const time::time_t time) {
 	return this->cost_field->is_dirty(time);
 }
 
diff --git a/libopenage/pathfinding/sector.h b/libopenage/pathfinding/sector.h
index cc2950f25e..e0f751b70d 100644
--- a/libopenage/pathfinding/sector.h
+++ b/libopenage/pathfinding/sector.h
@@ -109,7 +109,7 @@ class Sector {
 	 * 
 	 * @param time Specified time to check.
 	 */
-	bool is_dirty(time::time_t time);
+	bool is_dirty(const time::time_t time);
 
 private:
 	/**
diff --git a/libopenage/pathfinding/tests.cpp b/libopenage/pathfinding/tests.cpp
index 6ec26b392d..2ac0960c34 100644
--- a/libopenage/pathfinding/tests.cpp
+++ b/libopenage/pathfinding/tests.cpp
@@ -24,7 +24,7 @@ void flow_field() {
 	// | 1 | 1 | 1 |
 	// | 1 | X | 1 |
 	// | 1 | 1 | 1 |
-	time::time_t time = time::TIME_ZERO;
+	const time::time_t time = time::TIME_ZERO;
 	cost_field->set_costs({1, 1, 1, 1, 255, 1, 1, 1, 1}, time);
 
 	// Test the different field types

From 5a17e4e65e235bcef005a44b31ca1369e640414b Mon Sep 17 00:00:00 2001
From: dmwever <56411717+dmwever@users.noreply.github.com>
Date: Thu, 5 Dec 2024 20:28:14 -0600
Subject: [PATCH 4/9] change sector is_dirty to a reference

---
 libopenage/pathfinding/sector.cpp | 2 +-
 libopenage/pathfinding/sector.h   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/libopenage/pathfinding/sector.cpp b/libopenage/pathfinding/sector.cpp
index 4556fd42c3..2da73690c0 100644
--- a/libopenage/pathfinding/sector.cpp
+++ b/libopenage/pathfinding/sector.cpp
@@ -249,7 +249,7 @@ void Sector::connect_exits() {
 	}
 }
 
-bool Sector::is_dirty(const time::time_t time) {
+bool Sector::is_dirty(const time::time_t &time) {
 	return this->cost_field->is_dirty(time);
 }
 
diff --git a/libopenage/pathfinding/sector.h b/libopenage/pathfinding/sector.h
index e0f751b70d..a8aad24c01 100644
--- a/libopenage/pathfinding/sector.h
+++ b/libopenage/pathfinding/sector.h
@@ -109,7 +109,7 @@ class Sector {
 	 * 
 	 * @param time Specified time to check.
 	 */
-	bool is_dirty(const time::time_t time);
+	bool is_dirty(const time::time_t &time);
 
 private:
 	/**

From 22e594f80c131e6758dc3d26714da1d5e2336ed6 Mon Sep 17 00:00:00 2001
From: dmwever <56411717+dmwever@users.noreply.github.com>
Date: Thu, 5 Dec 2024 22:56:07 -0600
Subject: [PATCH 5/9] Change fieldCache to unique_ptr and add docs

---
 libopenage/pathfinding/field_cache.h | 1 -
 libopenage/pathfinding/integrator.h  | 6 +++++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/libopenage/pathfinding/field_cache.h b/libopenage/pathfinding/field_cache.h
index a1f43a563e..87dbdf60f9 100644
--- a/libopenage/pathfinding/field_cache.h
+++ b/libopenage/pathfinding/field_cache.h
@@ -55,7 +55,6 @@ class FieldCache
 	 * cleared of dynamic flags, i.e. wavefront or LOS flags. These have to be recalculated
 	 * when the field is reused.
 	 */
-
 	std::unordered_map<std::pair<portal_id_t, sector_id_t>,
 	                   get_return_t,
 	                   pair_hash>
diff --git a/libopenage/pathfinding/integrator.h b/libopenage/pathfinding/integrator.h
index 690c525ad7..7d09c00a73 100644
--- a/libopenage/pathfinding/integrator.h
+++ b/libopenage/pathfinding/integrator.h
@@ -128,7 +128,11 @@ class Integrator {
 					 bool evict_cache = false);
 
 private:
-	std::shared_ptr<FieldCache> field_cache;
+	
+	/**
+	 * Cache for already computed fields.
+	 */
+	std::unique_ptr<FieldCache> field_cache;
 };
 
 } // namespace path

From ce77c9fe02b653c03d2b6bfd448e4306cfd78635 Mon Sep 17 00:00:00 2001
From: dmwever <56411717+dmwever@users.noreply.github.com>
Date: Thu, 5 Dec 2024 22:57:25 -0600
Subject: [PATCH 6/9] Grammar

Co-authored-by: Christoph Heine <6852422+heinezen@users.noreply.github.com>
---
 libopenage/pathfinding/path.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libopenage/pathfinding/path.h b/libopenage/pathfinding/path.h
index ca6391bf67..8be7f802f7 100644
--- a/libopenage/pathfinding/path.h
+++ b/libopenage/pathfinding/path.h
@@ -37,7 +37,7 @@ struct Path {
 	/// First waypoint is the start position of the path request.
 	/// Last waypoint is the target position of the path request.
 	std::vector<coord::tile> waypoints;
-	/// Time path was created.
+	/// Time the path was created.
 	const time::time_t time;
 };
 

From d33d4f750cd18190f2e51da0364aea8ae85e873d Mon Sep 17 00:00:00 2001
From: dmwever <56411717+dmwever@users.noreply.github.com>
Date: Thu, 5 Dec 2024 22:57:41 -0600
Subject: [PATCH 7/9] Grammar

Co-authored-by: Christoph Heine <6852422+heinezen@users.noreply.github.com>
---
 libopenage/pathfinding/path.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libopenage/pathfinding/path.h b/libopenage/pathfinding/path.h
index 8be7f802f7..2d1f1cd593 100644
--- a/libopenage/pathfinding/path.h
+++ b/libopenage/pathfinding/path.h
@@ -21,7 +21,7 @@ struct PathRequest {
 	coord::tile start;
 	/// Target position of the path.
 	coord::tile target;
-	/// Time request was made.
+	/// Time the request was made.
 	const time::time_t time;
 };
 

From 3adb80210e7c5ca52d6deefe8a0c8c2ab20708d5 Mon Sep 17 00:00:00 2001
From: dmwever <56411717+dmwever@users.noreply.github.com>
Date: Thu, 5 Dec 2024 23:03:37 -0600
Subject: [PATCH 8/9] Use contains()

Co-authored-by: Christoph Heine <6852422+heinezen@users.noreply.github.com>
---
 libopenage/pathfinding/field_cache.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/libopenage/pathfinding/field_cache.cpp b/libopenage/pathfinding/field_cache.cpp
index a798e9fbd7..81b21c8264 100644
--- a/libopenage/pathfinding/field_cache.cpp
+++ b/libopenage/pathfinding/field_cache.cpp
@@ -15,8 +15,7 @@ void FieldCache::evict(std::pair<unsigned long long, unsigned long long> cache_k
 }
 
 bool FieldCache::is_cached(std::pair<unsigned long long, unsigned long long> cache_key) {
-    auto cached = this->cache.find(cache_key);
-    return cached != this->cache.end();
+    return this->cache.contains(cache_key);
 }
 
 std::shared_ptr<IntegrationField> FieldCache::get_integration_field(std::pair<unsigned long long, unsigned long long> cache_key) {

From fd72608ddceb27d52214192ca2999f711acea337 Mon Sep 17 00:00:00 2001
From: dmwever <56411717+dmwever@users.noreply.github.com>
Date: Sat, 7 Dec 2024 12:04:36 -0600
Subject: [PATCH 9/9] several changes

---
 libopenage/gamestate/map.cpp           |  2 +-
 libopenage/pathfinding/cost_field.cpp  | 31 ++++++++---------
 libopenage/pathfinding/cost_field.h    | 21 +++++-------
 libopenage/pathfinding/field_cache.cpp | 27 ++++++++-------
 libopenage/pathfinding/field_cache.h   | 46 +++++++++++++++++---------
 libopenage/pathfinding/integrator.cpp  | 22 ++++++------
 libopenage/pathfinding/types.h         | 15 +++++++++
 7 files changed, 92 insertions(+), 72 deletions(-)

diff --git a/libopenage/gamestate/map.cpp b/libopenage/gamestate/map.cpp
index 8300ce273d..88578fabdb 100644
--- a/libopenage/gamestate/map.cpp
+++ b/libopenage/gamestate/map.cpp
@@ -49,7 +49,7 @@ Map::Map(const std::shared_ptr<GameState> &state,
 
 				auto sector = grid->get_sector(chunk_idx);
 				auto cost_field = sector->get_cost_field();
-				cost_field->set_cost(tile_idx, path_cost.second);
+				cost_field->set_cost(tile_idx, path_cost.second, time::TIME_ZERO);
 			}
 		}
 	}
diff --git a/libopenage/pathfinding/cost_field.cpp b/libopenage/pathfinding/cost_field.cpp
index c211d169c1..d737f550c0 100644
--- a/libopenage/pathfinding/cost_field.cpp
+++ b/libopenage/pathfinding/cost_field.cpp
@@ -14,7 +14,7 @@ namespace openage::path {
 CostField::CostField(size_t size) :
 	size{size},
 	cells(this->size * this->size, COST_MIN),
-	changed{time::TIME_MIN} {
+	valid_until{time::TIME_MIN} {
 	log::log(DBG << "Created cost field with size " << this->size << "x" << this->size);
 }
 
@@ -34,42 +34,39 @@ cost_t CostField::get_cost(size_t idx) const {
 	return this->cells.at(idx);
 }
 
-void CostField::set_cost(const coord::tile_delta &pos, cost_t cost, const time::time_t &changed) {
-	this->cells[pos.ne + pos.se * this->size] = cost;
-	this->changed = changed;
+void CostField::set_cost(const coord::tile_delta &pos, cost_t cost, const time::time_t &valid_until) {
+	this->set_cost(pos.ne + pos.se * this->size, cost, valid_until);
 }
 
-void CostField::set_cost(size_t x, size_t y, cost_t cost, const time::time_t &changed) {
-	this->cells[x + y * this->size] = cost;
-	this->changed = changed;
+void CostField::set_cost(size_t x, size_t y, cost_t cost, const time::time_t &valid_until) {
+	this->set_cost(x + y * this->size, cost, valid_until);
 }
 
-void CostField::set_cost(size_t idx, cost_t cost) {
+inline void CostField::set_cost(size_t idx, cost_t cost, const time::time_t &valid_until) {
 	this->cells[idx] = cost;
-	this->changed = time::TIME_ZERO;
-}
-
-void CostField::set_cost(size_t idx, cost_t cost, const time::time_t &changed) {
-	this->cells[idx] = cost;
-	this->changed = changed;
+	this->valid_until = valid_until;
 }
 
 const std::vector<cost_t> &CostField::get_costs() const {
 	return this->cells;
 }
 
-void CostField::set_costs(std::vector<cost_t> &&cells, const time::time_t &changed) {
+void CostField::set_costs(std::vector<cost_t> &&cells, const time::time_t &valid_until) {
 	ENSURE(cells.size() == this->cells.size(),
 	       "cells vector has wrong size: " << cells.size()
 	                                       << "; expected: "
 	                                       << this->cells.size());
 
 	this->cells = std::move(cells);
-	this->changed = changed;
+	this->valid_until = valid_until;
 }
 
 bool CostField::is_dirty(const time::time_t &time) {
-	return time <= this->changed;
+	return time >= this->valid_until;
+}
+
+void CostField::clean() {
+	this->valid_until = time::TIME_MAX;
 }
 
 } // namespace openage::path
diff --git a/libopenage/pathfinding/cost_field.h b/libopenage/pathfinding/cost_field.h
index e62496acf1..f70adf9251 100644
--- a/libopenage/pathfinding/cost_field.h
+++ b/libopenage/pathfinding/cost_field.h
@@ -79,14 +79,6 @@ class CostField {
 	 */
 	void set_cost(size_t x, size_t y, cost_t cost, const time::time_t &changed);
 
-	/**
-	 * Set the cost at a specified position.
-	 *
-	 * @param idx Index of the cell.
-	 * @param cost Cost to set.
-	 */
-	void set_cost(size_t idx, cost_t cost);
-
 	/**
 	 * Set the cost at a specified position.
 	 *
@@ -94,7 +86,7 @@ class CostField {
 	 * @param cost Cost to set.
 	 * @param changed Time at which the cost value is changed.
 	 */
-	void set_cost(size_t idx, cost_t cost, const time::time_t &changed);
+	inline void set_cost(size_t idx, cost_t cost, const time::time_t &changed);
 
 	/**
 	 * Get the cost field values.
@@ -113,11 +105,16 @@ class CostField {
 
 	/**
 	 * Check if the cost field is dirty at the specified time.
-	 * 
-	 * @param time Cost field is dirty if the cost field is accessed before the latest change to the cost field.
+	 *
+	 * @param time Cost field is dirty if the cost field is accessed after the time given in valid_until.
 	 */
 	bool is_dirty(const time::time_t &time);
 
+	/**
+	 * Cleans the dirty flag by setting it to time_MAX.
+	 */
+	void clean();
+
 private:
 	/**
 	 * Side length of the field.
@@ -127,7 +124,7 @@ class CostField {
 	/**
 	 * Time the cost field was last changed.
 	 */
-	const time::time_t changed;
+	time::time_t &valid_until;
 
 	/**
 	 * Cost field values.
diff --git a/libopenage/pathfinding/field_cache.cpp b/libopenage/pathfinding/field_cache.cpp
index 81b21c8264..95276b0818 100644
--- a/libopenage/pathfinding/field_cache.cpp
+++ b/libopenage/pathfinding/field_cache.cpp
@@ -4,28 +4,27 @@
 
 namespace openage::path {
 
-void FieldCache::add(std::pair<unsigned long long, unsigned long long> cache_key,
-            std::shared_ptr<IntegrationField> &integration_field,
-            std::shared_ptr<FlowField> &flow_field) {
-    this->cache[cache_key] = std::make_pair(integration_field, flow_field);
+void FieldCache::add(cache_key_t cache_key,
+                     field_cache_t cache_entry) {
+	this->cache[cache_key] = cache_entry;
 }
 
-void FieldCache::evict(std::pair<unsigned long long, unsigned long long> cache_key) {
-    this->cache.erase(cache_key);
+void FieldCache::evict(cache_key_t cache_key) {
+	this->cache.erase(cache_key);
 }
 
-bool FieldCache::is_cached(std::pair<unsigned long long, unsigned long long> cache_key) {
-    return this->cache.contains(cache_key);
+bool FieldCache::is_cached(cache_key_t cache_key) {
+	return this->cache.contains(cache_key);
 }
 
-std::shared_ptr<IntegrationField> FieldCache::get_integration_field(std::pair<unsigned long long, unsigned long long> cache_key) {
-    auto cached = this->cache.find(cache_key);
-    return cached->second.first;
+std::shared_ptr<IntegrationField> FieldCache::get_integration_field(cache_key_t cache_key) {
+	auto cached = this->cache.find(cache_key);
+	return cached->second.first;
 }
 
-std::shared_ptr<FlowField> FieldCache::get_flow_field(std::pair<unsigned long long, unsigned long long> cache_key) {
-    auto cached = this->cache.find(cache_key);
-    return cached->second.second;
+std::shared_ptr<FlowField> FieldCache::get_flow_field(cache_key_t cache_key) {
+	auto cached = this->cache.find(cache_key);
+	return cached->second.second;
 }
 
 } // namespace openage::path
diff --git a/libopenage/pathfinding/field_cache.h b/libopenage/pathfinding/field_cache.h
index 87dbdf60f9..23374e5123 100644
--- a/libopenage/pathfinding/field_cache.h
+++ b/libopenage/pathfinding/field_cache.h
@@ -17,25 +17,39 @@ namespace path {
 class IntegrationField;
 class FlowField;
 
-class FieldCache
-{
+/**
+ * Cache to store already calculated flow and integration fields for the pathfinding algorithm.
+ */
+class FieldCache {
 public:
-    FieldCache() = default;
-    ~FieldCache() = default;
+	FieldCache() = default;
+	~FieldCache() = default;
 
-    void add(std::pair<unsigned long long, unsigned long long> cache_key,
-             std::shared_ptr<IntegrationField> &integration_field,
-             std::shared_ptr<FlowField> &flow_field);
+	/**
+	 * Adds a new field cache entry to the cache with a given portal and sector cache key.
+	 */
+	void add(cache_key_t cache_key,
+	         field_cache_t cache_entry);
 
-	void evict(std::pair<unsigned long long, unsigned long long> cache_key);
+	/**
+	 * Evicts a given field cache entry from the cache at the given cache key.
+	 */
+	void evict(cache_key_t cache_key);
 
-    bool is_cached(std::pair<unsigned long long, unsigned long long> cache_key);
+	/**
+	 * Checks if there is a cached entry at a specific cache key.
+	 */
+	bool is_cached(cache_key_t cache_key);
 
-    std::shared_ptr<IntegrationField> get_integration_field(std::pair<unsigned long long, unsigned long long> cache_key);
-    
-    std::shared_ptr<FlowField> get_flow_field(std::pair<unsigned long long, unsigned long long> cache_key);
-    
-    using get_return_t = std::pair<std::shared_ptr<IntegrationField>, std::shared_ptr<FlowField>>;
+	/**
+	 * Gets the integration field from a given cache entry.
+	 */
+	std::shared_ptr<IntegrationField> get_integration_field(cache_key_t cache_key);
+
+	/**
+	 * Gets the flow field from a given cache entry.
+	 */
+	std::shared_ptr<FlowField> get_flow_field(cache_key_t cache_key);
 
 private:
 	/**
@@ -55,8 +69,8 @@ class FieldCache
 	 * cleared of dynamic flags, i.e. wavefront or LOS flags. These have to be recalculated
 	 * when the field is reused.
 	 */
-	std::unordered_map<std::pair<portal_id_t, sector_id_t>,
-	                   get_return_t,
+	std::unordered_map<cache_key_t,
+	                   field_cache_t,
 	                   pair_hash>
 		cache;
 };
diff --git a/libopenage/pathfinding/integrator.cpp b/libopenage/pathfinding/integrator.cpp
index d91ac9ecb7..e164f3a094 100644
--- a/libopenage/pathfinding/integrator.cpp
+++ b/libopenage/pathfinding/integrator.cpp
@@ -5,10 +5,10 @@
 #include "log/log.h"
 
 #include "pathfinding/cost_field.h"
+#include "pathfinding/field_cache.h"
 #include "pathfinding/flow_field.h"
 #include "pathfinding/integration_field.h"
 #include "pathfinding/portal.h"
-#include "pathfinding/field_cache.h"
 
 
 namespace openage::path {
@@ -38,17 +38,16 @@ std::shared_ptr<IntegrationField> Integrator::integrate(const std::shared_ptr<Co
                                                         const std::shared_ptr<Portal> &portal,
                                                         const coord::tile_delta &target,
                                                         bool with_los,
-											 			bool evict_cache) {
+                                                        bool evict_cache) {
 	auto cache_key = std::make_pair(portal->get_id(), other_sector_id);
 	if (evict_cache) {
 		this->field_cache->evict(cache_key);
 	}
-	if (this->field_cache->is_cached(cache_key)) {
+	else if (this->field_cache->is_cached(cache_key)) {
 		log::log(DBG << "Using cached integration field for portal " << portal->get_id()
 		             << " from sector " << other_sector_id);
-					 
 
-		//retrieve cached integration field
+		// retrieve cached integration field
 		auto cached_integration_field = this->field_cache->get_integration_field(cache_key);
 
 		if (with_los) {
@@ -107,16 +106,16 @@ std::shared_ptr<FlowField> Integrator::build(const std::shared_ptr<IntegrationFi
                                              sector_id_t other_sector_id,
                                              const std::shared_ptr<Portal> &portal,
                                              bool with_los,
-											 bool evict_cache) {
+                                             bool evict_cache) {
 	auto cache_key = std::make_pair(portal->get_id(), other_sector_id);
 	if (evict_cache) {
 		this->field_cache->evict(cache_key);
 	}
-	if (this->field_cache->is_cached(cache_key)) {
+	else if (this->field_cache->is_cached(cache_key)) {
 		log::log(DBG << "Using cached flow field for portal " << portal->get_id()
 		             << " from sector " << other_sector_id);
 
-		//retrieve cached flow field
+		// retrieve cached flow field
 		auto cached_flow_field = this->field_cache->get_flow_field(cache_key);
 
 		if (with_los) {
@@ -157,17 +156,16 @@ Integrator::get_return_t Integrator::get(const std::shared_ptr<CostField> &cost_
                                          const std::shared_ptr<Portal> &portal,
                                          const coord::tile_delta &target,
                                          bool with_los,
-										 bool evict_cache) {
+                                         bool evict_cache) {
 	auto cache_key = std::make_pair(portal->get_id(), other_sector_id);
 	if (evict_cache) {
 		this->field_cache->evict(cache_key);
 	}
-	if (this->field_cache->is_cached(cache_key)) {
+	else if (this->field_cache->is_cached(cache_key)) {
 		log::log(DBG << "Using cached integration and flow fields for portal " << portal->get_id()
 		             << " from sector " << other_sector_id);
 
-		
-		//retrieve cached fields
+		// retrieve cached fields
 		auto cached_integration_field = this->field_cache->get_integration_field(cache_key);
 		auto cached_flow_field = this->field_cache->get_flow_field(cache_key);
 
diff --git a/libopenage/pathfinding/types.h b/libopenage/pathfinding/types.h
index 1b48a49654..3229010a91 100644
--- a/libopenage/pathfinding/types.h
+++ b/libopenage/pathfinding/types.h
@@ -4,6 +4,8 @@
 
 #include <cstddef>
 #include <cstdint>
+#include <memory>
+#include <utility>
 
 
 namespace openage::path {
@@ -109,4 +111,17 @@ using sector_id_t = size_t;
  */
 using portal_id_t = size_t;
 
+class FlowField;
+class IntegrationField;
+
+/**
+ * Cache key for accessing the field cache using a portal id and a sector id.
+ */
+using cache_key_t = std::pair<portal_id_t, sector_id_t>;
+
+/**
+ * Returnable field cache entry pair containing an integration field and a flow field.
+ */
+using field_cache_t = std::pair<std::shared_ptr<IntegrationField>, std::shared_ptr<FlowField>>;
+
 } // namespace openage::path