Support for straight trail

docs/Fixed-or-Improved-Logics.md

@@ -156,9 +156,12 @@ Bolt.Disable3=false    ; boolean
 ### Customizable projectile gravity
 
 -  You can now specify individual projectile gravity.
+    - Set `Gravity=0` with an arcing projectile can create a straight trail.
+        - Set `Gravity.HeightFix=true` allows the projectile to hit target which is not at the same height while `Gravity=0`.
 
 In `rulesmd.ini`:
 ```ini
-[SOMEPROJECTILE] ; Projectile
-Gravity=6.0      ; double
+[SOMEPROJECTILE]        ; Projectile
+Gravity=6.0             ; double
+Gravity.HeightFix=false ; boolean
 ```

src/Ext/Bullet/Hooks.cpp

@@ -151,4 +151,29 @@ DEFINE_HOOK(0x773087, WeaponTypeClass_GetSpeed_ApplyGravity, 0x6)
 	__asm { fld nGravity };
 
 	return 0x7730A3;
+}
+
+DEFINE_HOOK(0x6FF031, TechnoClass_FireAt_ReverseVelocityWhileGravityIsZero, 0xA)
+{
+	GET(BulletClass*, pBullet, EBX);
+
+	auto const pData = BulletTypeExt::ExtMap.Find(pBullet->Type);
+
+	if (pBullet->Type->Arcing && BulletTypeExt::GetAdjustedGravity(pBullet->Type) == 0.0)
+	{
+		pBullet->Velocity *= -1;
+		if (pData->Gravity_HeightFix)
+		{
+			auto speed = pBullet->Velocity.Magnitude();
+
+			pBullet->Velocity.X = static_cast<double>(pBullet->TargetCoords.X - pBullet->SourceCoords.X);
+			pBullet->Velocity.Y = static_cast<double>(pBullet->TargetCoords.Y - pBullet->SourceCoords.Y);
+			pBullet->Velocity.Z = static_cast<double>(pBullet->TargetCoords.Z - pBullet->SourceCoords.Z);
+
+			auto magnitude = pBullet->Velocity.Magnitude();
+			pBullet->Velocity *= speed / magnitude;
+		}
+	}
+
+	return 0;
 }

src/Ext/BulletType/Body.cpp

@@ -25,6 +25,7 @@ void BulletTypeExt::ExtData::LoadFromINIFile(CCINIClass* const pINI)
 
 	this->Interceptable.Read(exINI, pSection, "Interceptable");
 	this->Gravity.Read(exINI, pSection, "Gravity");
+	this->Gravity_HeightFix.Read(exINI, pSection, "Gravity.HeightFix");
 
 	INI_EX exArtINI(CCINIClass::INI_Art);
 
@@ -41,6 +42,7 @@ void BulletTypeExt::ExtData::Serialize(T& Stm)
 		.Process(this->Interceptable)
 		.Process(this->LaserTrail_Types)
 		.Process(this->Gravity)
+		.Process(this->Gravity_HeightFix)
 		;
 }
 

src/Ext/BulletType/Body.h

@@ -18,11 +18,13 @@ class BulletTypeExt
 		Valueable<bool> Interceptable;
 		ValueableIdxVector<LaserTrailTypeClass> LaserTrail_Types;
 		Nullable<double> Gravity;
+		Valueable<bool> Gravity_HeightFix;
 
 		ExtData(BulletTypeClass* OwnerObject) : Extension<BulletTypeClass>(OwnerObject),
 			Interceptable(false),
 			LaserTrail_Types(),
-			Gravity()
+			Gravity(),
+			Gravity_HeightFix(false)
 		{ }
 
 		virtual ~ExtData() = default;