6 files changed, 103 insertions, 12 deletions
diff --git a/universe/CMakeLists.txt b/universe/CMakeLists.txt
index 1728f1c..c3d56f8 100644
--- a/universe/CMakeLists.txt
+++ b/universe/CMakeLists.txt
@@ -15,3 +15,13 @@ add_resources(
 	resources/universe/ship_types.json
 	resources/universe/turret_types.json
 )
+add_executable(
+	${PROJECT_NAME}_test
+	tests/TurretType.cpp
+)
+target_link_libraries(
+	${PROJECT_NAME}_test
+	PRIVATE ${PROJECT_NAME}
+	PRIVATE GTest::gtest_main
+)
+gtest_discover_tests(${PROJECT_NAME}_test)
diff --git a/universe/include/kurator/universe/TurretType.h b/universe/include/kurator/universe/TurretType.h
index c7ba5a3..7b3ebdc 100644
--- a/universe/include/kurator/universe/TurretType.h
+++ b/universe/include/kurator/universe/TurretType.h
@@ -19,7 +19,12 @@ struct TurretType
 	double optimal_range = 0.0;
 	double falloff_modifier = 0.05;
 	double falloff_intensity = 0.2;
-	double effective_damage(double distance) const;
+	double tracking = 1000;
+	double tracking_factor = 3.0;
+	double tracking_exponent = 0.5;
+	double effective_damage(double distance, double speed) const;
+	double range_modifier(double distance) const;
+	double tracking_modifier(double distance, double speed) const;
 	double effective_range() const;
 	double damage_per_second() const;
 };
diff --git a/universe/resources/universe/turret_types.json b/universe/resources/universe/turret_types.json
index 0b4e3ca..0004ef1 100644
--- a/universe/resources/universe/turret_types.json
+++ b/universe/resources/universe/turret_types.json
@@ -6,7 +6,8 @@
 		"rate_of_fire": 4.5,
 		"reload": 0.0,
 		"optimal_range": 7000.0,
-		"falloff_modifier": 0.05
+		"falloff_modifier": 0.05,
+		"tracking": 150.0
 	},
 	{
 		"name": "BurstLaser",
@@ -15,7 +16,8 @@
 		"rate_of_fire": 0.25,
 		"reload": 2.75,
 		"optimal_range": 3500.0,
-		"falloff_modifier": 0.05
+		"falloff_modifier": 0.05,
+		"tracking": 260.0
 	},
 	{
 		"name": "GaussCannon",
@@ -24,7 +26,8 @@
 		"rate_of_fire": 0.0,
 		"reload": 5.5,
 		"optimal_range": 12000.0,
-		"falloff_modifier": 0.2
+		"falloff_modifier": 0.2,
+		"tracking": 35.0
 	},
 	{
 		"name": "Autocannon",
@@ -33,7 +36,8 @@
 		"rate_of_fire": 0.15,
 		"reload": 1.5,
 		"optimal_range": 2000,
-		"falloff_modifier": 0.8
+		"falloff_modifier": 0.8,
+		"tracking": 350.0
 	},
 	{
 		"name": "Howitzer",
@@ -42,7 +46,8 @@
 		"rate_of_fire": 7.5,
 		"reload": 0,
 		"optimal_range": 5600,
-		"falloff_modifier": 0.5
+		"falloff_modifier": 0.5,
+		"tracking": 60.0
 	},
 	{
 		"name": "Blaster",
@@ -51,6 +56,7 @@
 		"rate_of_fire": 0,
 		"reload": 2,
 		"optimal_range": 750,
-		"falloff_modifier": 0.45
+		"falloff_modifier": 0.45,
+		"tracking": 450.0
 	}
 ]
diff --git a/universe/src/JsonRepository.cpp b/universe/src/JsonRepository.cpp
index 5d15646..dbfb8ea 100644
--- a/universe/src/JsonRepository.cpp
+++ b/universe/src/JsonRepository.cpp
@@ -56,6 +56,9 @@ from_json(const json& item, TurretType& turret)
 	maybe_to(item, "optimal_range", turret.optimal_range);
 	maybe_to(item, "falloff_modifier", turret.falloff_modifier);
 	maybe_to(item, "falloff_intensity", turret.falloff_intensity);
+	maybe_to(item, "tracking", turret.tracking);
+	maybe_to(item, "tracking_factor", turret.tracking_factor);
+	maybe_to(item, "tracking_exponent", turret.tracking_exponent);
 }
 
 
diff --git a/universe/src/TurretType.cpp b/universe/src/TurretType.cpp
index 78887d7..4da47ef 100644
--- a/universe/src/TurretType.cpp
+++ b/universe/src/TurretType.cpp
@@ -11,20 +11,38 @@ namespace universe
 
 
 double
-TurretType::effective_damage(const double distance) const
+TurretType::effective_damage(const double distance, const double speed) const
+{
+	return base_damage * std::round(range_modifier(distance) * tracking_modifier(distance, speed) * 1000) / 1000;
+}
+
+
+double
+TurretType::range_modifier(const double distance) const
 {
 	const auto overflow = distance - optimal_range;
 	const auto falloff = std::max(0.0, overflow / optimal_range / falloff_modifier);
-	return base_damage * std::round(std::pow(falloff_intensity, std::pow(falloff, 2)) * 1000) / 1000;
+	return std::pow(falloff_intensity, std::pow(falloff, 2));
+}
+
+
+double
+TurretType::tracking_modifier(const double distance, const double speed) const
+{
+	const auto simplified_falloff = optimal_range + optimal_range * falloff_modifier;
+	const auto by_distance = (distance + 1.0) / simplified_falloff;
+	const auto by_speed = tracking / (speed + 1.0);
+	return std::min(1.0, std::pow(tracking_factor * by_distance * by_speed, tracking_exponent));
 }
 
 
 double
 TurretType::effective_range() const
 {
-	const double target_falloff = std::sqrt(std::log2(0.01) / std::log2(falloff_intensity));
-	const double one_percent_overflow = target_falloff * falloff_modifier * optimal_range;
-	return one_percent_overflow + optimal_range;
+	const double one_point = 1.0 / base_damage;
+	const double target_falloff = std::sqrt(std::log2(one_point) / std::log2(falloff_intensity));
+	const double one_point_overflow = target_falloff * falloff_modifier * optimal_range;
+	return one_point_overflow + optimal_range;
 }
 
 
diff --git a/universe/tests/TurretType.cpp b/universe/tests/TurretType.cpp
new file mode 100644
index 0000000..7ce70c0
--- /dev/null
+++ b/universe/tests/TurretType.cpp
@@ -0,0 +1,49 @@
+#include <gtest/gtest.h>
+
+#include <kurator/universe/TurretType.h>
+
+
+namespace kurator
+{
+namespace tests
+{
+
+
+const universe::TurretType LOW {
+	"",
+	1,
+	10.0,
+	1.0,
+	0.0,
+	1000.0,
+	0.05,
+	0.2,
+};
+
+
+const universe::TurretType HIGH {
+	"",
+	1,
+	1000.0,
+	1.0,
+	0.0,
+	1000.0,
+	0.05,
+	0.2,
+};
+
+
+
+TEST(TurretType, effective_range)
+{
+	const auto low = LOW.effective_range();
+	EXPECT_LE(1.0, LOW.range_modifier(low - 1.0) * LOW.base_damage);
+	EXPECT_GE(1.0, LOW.range_modifier(low + 1.0) * LOW.base_damage);
+	const auto high = HIGH.effective_range();
+	EXPECT_LE(1.0, HIGH.range_modifier(high - 1.0) * HIGH.base_damage);
+	EXPECT_GE(1.0, HIGH.range_modifier(high + 1.0) * HIGH.base_damage);
+}
+
+
+}  // namespace tests
+}  // namespace kurator