feat: Ability to limit turret firing arc (#7094)

* Introduce a capability to limit the rotation of a turret.

Co-authored-by: Hurleveur <94366726+Hurleveur@users.noreply.github.com>
Co-authored-by: oo13 <ooyooxei+gh@gmail.com>
Co-authored-by: OOTA, Masato <ooyooxei+gh@gmail.com>
Co-authored-by: Rising Leaf <85687254+RisingLeaf@users.noreply.github.com>
Co-authored-by: tehhowch <tehhowch@users.noreply.github.com>
Co-authored-by: tibetiroka <68112292+tibetiroka@users.noreply.github.com>
Co-authored-by: TomGoodIdea <108272452+TomGoodIdea@users.noreply.github.com>

data/_ui/tooltips.txt

@@ -990,6 +990,9 @@ tip "shots / second:"
 tip "turret turn rate:"
 	`Degrees this turret can turn per second.`
 
+tip "arc:"
+	`The angular range of protection provided by this weapon, in degrees.`
+
 tip "homing:"
 	`This projectile's ability to track its target. Weapons with better homing can adjust to the target's speed to plot a more effective intercept course.`
 

source/AI.cpp

@@ -3357,7 +3357,7 @@ void AI::AimTurrets(const Ship &ship, FireCommand &command, bool opportunistic)
 			{
 				// Get the index of this weapon.
 				int index = &hardpoint - &ship.Weapons().front();
-				double offset = (hardpoint.HarmonizedAngle() - hardpoint.GetAngle()).Degrees();
+				double offset = (hardpoint.GetIdleAngle() - hardpoint.GetAngle()).Degrees();
 				command.SetAim(index, offset / hardpoint.GetOutfit()->TurretTurn());
 			}
 		return;
@@ -3375,8 +3375,12 @@ void AI::AimTurrets(const Ship &ship, FireCommand &command, bool opportunistic)
 				if(!previous && (Random::Int(60)))
 					continue;
 
-				Angle centerAngle = Angle(hardpoint.GetPoint());
-				double bias = (centerAngle - hardpoint.GetAngle()).Degrees() / 180.;
+				// Sweep between the min and max arc.
+				Angle centerAngle = Angle(hardpoint.GetIdleAngle());
+				const Angle minArc = hardpoint.GetMinArc();
+				const Angle maxArc = hardpoint.GetMaxArc();
+				const double arcMiddleDegrees = (minArc.AbsDegrees() + maxArc.AbsDegrees()) / 2.;
+				double bias = (centerAngle - hardpoint.GetAngle()).Degrees() / min(arcMiddleDegrees, 180.);
 				double acceleration = Random::Real() - Random::Real() + bias;
 				command.SetAim(index, previous + .1 * acceleration);
 			}
@@ -3438,7 +3442,32 @@ void AI::AimTurrets(const Ship &ship, FireCommand &command, bool opportunistic)
 				}
 
 				// Determine how much the turret must turn to face that vector.
-				double degrees = (Angle(p) - aim).Degrees();
+				double degrees = 0.;
+				Angle angleToPoint = Angle(p);
+				if(hardpoint.IsOmnidirectional())
+					degrees = (angleToPoint - aim).Degrees();
+				else
+				{
+					// For turret with limited arc, determine the turn up to the nearest arc limit.
+					// Also reduce priority of target if it's not within the firing arc.
+					const Angle facing = ship.Facing();
+					const Angle minArc = hardpoint.GetMinArc() + facing;
+					const Angle maxArc = hardpoint.GetMaxArc() + facing;
+					if(!angleToPoint.IsInRange(minArc, maxArc))
+					{
+						// Decrease the priority of the target.
+						rendezvousTime += 2. * weapon->TotalLifetime();
+
+						// Point to the nearer edge of the arc.
+						const double minDegree = (minArc - angleToPoint).Degrees();
+						const double maxDegree = (maxArc - angleToPoint).Degrees();
+						if(fabs(minDegree) < fabs(maxDegree))
+							angleToPoint = minArc;
+						else
+							angleToPoint = maxArc;
+					}
+					degrees = (angleToPoint - minArc).AbsDegrees() - (aim - minArc).AbsDegrees();
+				}
 				double turnTime = fabs(degrees) / weapon->TurretTurn();
 				// Always prefer targets that you are able to hit.
 				double score = turnTime + (180. / weapon->TurretTurn()) * rendezvousTime;

source/Angle.cpp

@@ -171,6 +171,14 @@ double Angle::Degrees() const
 
 
 
+// Convert an Angle object to degrees, in the range 0 to 360.
+double Angle::AbsDegrees() const
+{
+	return angle / DEG_TO_STEP;
+}
+
+
+
 // Return a point rotated by this angle around (0, 0).
 Point Angle::Rotate(const Point &point) const
 {
@@ -183,6 +191,19 @@ Point Angle::Rotate(const Point &point) const
 
 
 
+// Judge whether this is inside from "base" to "limit."
+// The range from "base" to "limit" is expressed by "clock" orientation.
+bool Angle::IsInRange(const Angle& base, const Angle& limit) const
+{
+	// Choose an edge of the arc as the reference angle (base) and
+	// compare relative angles to decide whether this is in the range.
+	Angle normalizedLimit = limit - base;
+	Angle normalizedTarget = *this - base;
+	return normalizedTarget.angle <= normalizedLimit.angle;
+}
+
+
+
 // Constructor using Angle's internal representation.
 Angle::Angle(const int32_t angle)
 	: angle(angle)

source/Angle.h

@@ -56,10 +56,16 @@ class Angle {
 	Point Unit() const;
 	// Convert an Angle object to degrees, in the range -180 to 180.
 	double Degrees() const;
+	// Convert an Angle object to degrees, in the range 0 to 360.
+	double AbsDegrees() const;
 
 	// Return a point rotated by this angle around (0, 0).
 	Point Rotate(const Point &point) const;
 
+	// Judge whether this is inside from "base" to "limit."
+	// The range from "base" to "limit" is expressed by "clock" orientation.
+	bool IsInRange(const Angle &base, const Angle &limit) const;
+
 
 private:
 	explicit Angle(int32_t angle);

source/Armament.cpp

@@ -30,17 +30,19 @@ using namespace std;
 
 
 // Add a gun hardpoint (fixed-direction weapon).
-void Armament::AddGunPort(const Point &point, const Angle &angle, bool isParallel, bool isUnder, const Outfit *outfit)
+void Armament::AddGunPort(const Point &point, const Hardpoint::BaseAttributes &attributes,
+	bool isUnder, const Outfit *outfit)
 {
-	hardpoints.emplace_back(point, angle, false, isParallel, isUnder, outfit);
+	hardpoints.emplace_back(point, attributes, false, isUnder, outfit);
 }
 
 
 
-// Add a turret hardpoint (omnidirectional weapon).
-void Armament::AddTurret(const Point &point, bool isUnder, const Outfit *outfit)
+// Add a turret hardpoint.
+void Armament::AddTurret(const Point &point, const Hardpoint::BaseAttributes &attributes,
+	bool isUnder, const Outfit *outfit)
 {
-	hardpoints.emplace_back(point, Angle(0.), true, false, isUnder, outfit);
+	hardpoints.emplace_back(point, attributes, true, isUnder, outfit);
 }
 
 

source/Armament.h

@@ -44,8 +44,10 @@ class Visual;
 class Armament {
 public:
 	// Add a gun or turret hard-point.
-	void AddGunPort(const Point &point, const Angle &angle, bool isParallel, bool isUnder, const Outfit *outfit = nullptr);
-	void AddTurret(const Point &point, bool isUnder, const Outfit *outfit = nullptr);
+	void AddGunPort(const Point &point, const Hardpoint::BaseAttributes &attributes,
+		bool isUnder, const Outfit *outfit = nullptr);
+	void AddTurret(const Point &point, const Hardpoint::BaseAttributes &attributes,
+		bool isUnder, const Outfit *outfit = nullptr);
 	// This must be called after all the outfit data is loaded. If you add more
 	// of a given weapon than there are slots for it, the extras will not fire.
 	// But, the "gun ports" attribute should keep that from happening. To

source/Hardpoint.cpp

@@ -44,10 +44,12 @@ namespace {
 
 
 // Constructor.
-Hardpoint::Hardpoint(const Point &point, const Angle &baseAngle, bool isTurret,
-	bool isParallel, bool isUnder, const Outfit *outfit)
-	: outfit(outfit), point(point * .5), baseAngle(baseAngle), isTurret(isTurret), isParallel(isParallel), isUnder(isUnder)
+Hardpoint::Hardpoint(const Point &point, const BaseAttributes &attributes,
+	bool isTurret, bool isUnder, const Outfit *outfit)
+	: outfit(outfit), point(point * .5), baseAngle(attributes.baseAngle), baseAttributes(attributes),
+	isTurret(isTurret), isParallel(baseAttributes.isParallel), isUnder(isUnder)
 {
+	UpdateArc();
 }
 
 
@@ -77,14 +79,31 @@ const Angle &Hardpoint::GetAngle() const
 
 
 
-// Get the default facing direction for a gun
-const Angle &Hardpoint::GetBaseAngle() const
+// Get the angle of a turret when idling, relative to the ship.
+// For guns, this function is equal to GetAngle().
+const Angle &Hardpoint::GetIdleAngle() const
 {
 	return baseAngle;
 }
 
 
 
+// Get the arc of fire if this is a directional turret,
+// otherwise a pair of 180 degree + baseAngle.
+const Angle &Hardpoint::GetMinArc() const
+{
+	return minArc;
+}
+
+
+
+const Angle &Hardpoint::GetMaxArc() const
+{
+	return maxArc;
+}
+
+
+
 // Get the angle this weapon ought to point at for ideal gun harmonization.
 Angle Hardpoint::HarmonizedAngle() const
 {
@@ -122,6 +141,13 @@ bool Hardpoint::IsParallel() const
 
 
 
+bool Hardpoint::IsOmnidirectional() const
+{
+	return isOmnidirectional;
+}
+
+
+
 bool Hardpoint::IsUnder() const
 {
 	return isUnder;
@@ -201,13 +227,25 @@ void Hardpoint::Step()
 
 
 // Adjust this weapon's aim by the given amount, relative to its maximum
-// "turret turn" rate.
+// "turret turn" rate. Up to its angle limit.
 void Hardpoint::Aim(double amount)
 {
 	if(!outfit)
 		return;
 
-	angle += outfit->TurretTurn() * amount;
+	const double add = outfit->TurretTurn() * amount;
+	if(isOmnidirectional)
+		angle += add;
+	else
+	{
+		const Angle newAngle = angle + add;
+		if(add < 0. && minArc.IsInRange(newAngle, angle))
+			angle = minArc;
+		else if(add > 0. && maxArc.IsInRange(angle, newAngle))
+			angle = maxArc;
+		else
+			angle += add;
+	}
 }
 
 
@@ -306,20 +344,23 @@ void Hardpoint::Install(const Outfit *outfit)
 		this->outfit = outfit;
 		Reload();
 
-		// For fixed weapons, apply "gun harmonization," pointing them slightly
-		// inward so the projectiles will converge. For turrets, start them out
-		// pointing outward from the center of the ship.
-		if(!isTurret)
+		// Update the arc of fire because of changing an outfit.
+		UpdateArc();
+
+		// For fixed weapons and idling turrets, apply "gun harmonization,"
+		// pointing them slightly inward so the projectiles will converge.
+		// Weapons that fire parallel beams don't get a harmonized angle.
+		// And some hardpoints/gunslots are configured not to get harmonized.
+		// So only harmonize when both the port and the outfit supports it.
+		if(!isParallel && !outfit->IsParallel())
 		{
-			angle = baseAngle;
-			// Weapons that fire in parallel beams don't get a harmonized angle.
-			// And some hardpoints/gunslots are configured not to get harmonized.
-			// So only harmonize when both the port and the outfit supports it.
-			if(!isParallel && !outfit->IsParallel())
-				angle += HarmonizedAngle();
+			const Angle harmonized = baseAngle + HarmonizedAngle();
+			// The harmonized angle might be out of the arc of a turret.
+			// If so, this turret is forced "parallel."
+			if(!isTurret || isOmnidirectional || harmonized.IsInRange(GetMinArc(), GetMaxArc()))
+				baseAngle = harmonized;
 		}
-		else
-			angle = Angle(point);
+		angle = baseAngle;
 	}
 }
 
@@ -339,6 +380,17 @@ void Hardpoint::Reload()
 void Hardpoint::Uninstall()
 {
 	outfit = nullptr;
+
+	// Update the arc of fire because of changing an outfit.
+	UpdateArc();
+}
+
+
+
+// Get the attributes that can be used as a parameter of the constructor when cloning this.
+const Hardpoint::BaseAttributes &Hardpoint::GetBaseAttributes() const
+{
+	return baseAttributes;
 }
 
 
@@ -350,20 +402,29 @@ bool Hardpoint::FireSpecialSystem(Ship &ship, const Body &body, std::vector<Visu
 	// Get the weapon range. Anti-missile and tractor beam shots always last a
 	// single frame, so their range is equal to their velocity.
 	double range = outfit->Velocity();
+	Angle facing = ship.Facing();
 
 	// Check if the body is within range of this hardpoint.
-	Point start = ship.Position() + ship.Facing().Rotate(point);
+	Point start = ship.Position() + facing.Rotate(point);
 	Point offset = body.Position() - start;
 	if(offset.Length() > range)
 		return false;
 
+	// Check if the target is within the arc of fire.
+	Angle aim(offset);
+	if(!isOmnidirectional)
+	{
+		const Angle minArc = GetMinArc() + facing;
+		const Angle maxArc = GetMaxArc() + facing;
+		if(!aim.IsInRange(minArc, maxArc))
+			return false;
+	}
+
 	// Precompute the number of visuals that will be added.
 	visuals.reserve(visuals.size() + outfit->FireEffects().size()
 		+ outfit->HitEffects().size() + outfit->DieEffects().size());
 
-	// Firing effects are displayed at the weapon hardpoint that just fired.
-	Angle aim(offset);
-	angle = aim - ship.Facing();
+	angle = aim - facing;
 	start += aim.Rotate(outfit->HardpointOffset());
 	CreateEffects(outfit->FireEffects(), start, ship.Velocity(), aim, visuals);
 
@@ -407,3 +468,53 @@ void Hardpoint::Fire(Ship &ship, const Point &start, const Angle &aim)
 	// case the outfit is its own ammunition.
 	ship.ExpendAmmo(*outfit);
 }
+
+
+
+// The arc depends on both the base hardpoint and the installed outfit.
+void Hardpoint::UpdateArc()
+{
+	if(!outfit)
+		return;
+
+	// Restore the initial value (from baseAttributes).
+	isOmnidirectional = baseAttributes.isOmnidirectional;
+	baseAngle = baseAttributes.baseAngle;
+	if(isOmnidirectional)
+	{
+		const Angle opposite = baseAngle + Angle(180.);
+		minArc = opposite;
+		maxArc = opposite;
+	}
+	else
+	{
+		minArc = baseAttributes.minArc;
+		maxArc = baseAttributes.maxArc;
+	}
+
+	// The installed weapon restricts the arc of fire.
+	const double hardpointsArc = (maxArc - minArc).AbsDegrees();
+	const double weaponsArc = outfit->Arc();
+	if(weaponsArc < 360. && (isOmnidirectional || weaponsArc < hardpointsArc))
+	{
+		isOmnidirectional = false;
+		const double weaponsHalf = weaponsArc / 2.;
+
+		// The base angle is placed as close to center as possible.
+		const Angle &firstAngle = minArc;
+		const Angle &secondAngle = maxArc;
+		double hardpointsMinArc = (baseAngle - firstAngle).AbsDegrees();
+		double hardpointsMaxArc = (secondAngle - baseAngle).AbsDegrees();
+		if(hardpointsMinArc < weaponsHalf)
+			hardpointsMaxArc = weaponsArc - hardpointsMinArc;
+		else if(hardpointsMaxArc < weaponsHalf)
+			hardpointsMinArc = weaponsArc - hardpointsMaxArc;
+		else
+		{
+			hardpointsMinArc = weaponsHalf;
+			hardpointsMaxArc = weaponsHalf;
+		}
+		minArc = baseAngle - hardpointsMinArc;
+		maxArc = baseAngle + hardpointsMaxArc;
+	}
+}