Implement variable transport speeds

changelog/snippets/features.6309.md

@@ -0,0 +1,16 @@
+- (#6309) The movement speed of transports now changes based on how many and which types of units they have loaded.
+    - Units slow down transports based on their `TransportSpeedReduction` stat. If a unit has a `TransportSpeedReduction` of 1, each instance of this unit will slow down the transport's `MaxAirspeed` by 1. The primary implication of this change is that the effectiveness of the currently too oppressive Zthuee drops is reduced in an intuitive way. The effectiveness of ACU drops via Tech 2 transports remains unchanged.
+
+        - TransportSpeedReduction: 0.15 (Tech 1 land units)
+        - TransportSpeedReduction: 0.3 (Tech 2 land units)
+        - TransportSpeedReduction: 0.6 (Tech 3 land units)
+        - TransportSpeedReduction: 1 (ACUs and SACUs)
+        - TransportSpeedReduction: 1 (Tech 4 land units for compatibility with survival maps)
+
+    - To prevent drops from being overnerfed by this change, the speeds of all transports is increased.
+
+        - MaxAirspeed: 10 --> 10.75 (Tech 1 transports)
+        - MaxAirspeed: 13.5 --> 14.5 (Tech 2 transports)
+        - MaxAirspeed: 15 --> 17.5 (The Continental)
+
+- (#6309) Display the `TransportSpeedReduction` stat in the additional unit details displayed when `Show Armament Detail in Build Menu` is enabled in the settings.

loc/US/strings_db.lua

@@ -6761,6 +6761,7 @@ uvd_0013="Vision: %d, Underwater Vision: %d, Regen: %0.1f, Cap Cost: %0.1f"
 uvd_0014="Damage: %.8g - %.8g, Splash: %.3g - %.3g"
 uvd_0015="Damage: %.8g x%d, Splash: %.3g"
 uvd_0016="Enhancements: %d"
+uvd_0017="Transport Speed Reduction: %.3g"
 
 uvd_DPS="(DPS: %d)"
 uvd_ManualFire="(Manual Fire)"

lua/sim/units/AirTransportUnit.lua

@@ -75,12 +75,25 @@ AirTransport = ClassUnit(AirUnit, BaseTransport) {
         end
     end,
 
+    ---@param self AirTransport
+    ---@param totalweight CargoWeight
+    ---@param unit Unit
+    ReduceTransportSpeed = function(self)
+        local transportspeed = self.Blueprint.Air.MaxAirspeed
+        local totalweight = 0
+        for _, unit in self:GetCargo() do
+            totalweight = totalweight + unit.Blueprint.Physics.TransportSpeedReduction
+	    end
+        self:SetSpeedMult(1 - (totalweight / transportspeed))
+    end,
+
     ---@param self AirTransport
     ---@param attachBone Bone
     ---@param unit Unit
     OnTransportAttach = function(self, attachBone, unit)
         AirUnitOnTransportAttach(self, attachBone, unit)
         BaseTransportOnTransportAttach(self, attachBone, unit)
+        self:ReduceTransportSpeed()
     end,
 
     ---@param self AirTransport
@@ -89,6 +102,7 @@ AirTransport = ClassUnit(AirUnit, BaseTransport) {
     OnTransportDetach = function(self, attachBone, unit)
         AirUnitOnTransportDetach(self, attachBone, unit)
         BaseTransportOnTransportDetach(self, attachBone, unit)
+        self:ReduceTransportSpeed()
     end,
 
     OnAttachedKilled = function(self, attached)

lua/system/blueprints-units.lua

@@ -161,6 +161,7 @@ local function PostProcessUnit(unit)
     local isDummy = unit.CategoriesHash['DUMMYUNIT']
     local isLand = unit.CategoriesHash['LAND']
     local isAir = unit.CategoriesHash['AIR']
+    local isNaval = unit.CategoriesHash['NAVAL']
     local isBomber = unit.CategoriesHash['BOMBER']
     local isGunship = unit.CategoriesHash['GROUNDATTACK'] and isAir and (not isBomber)
     local isTransport = unit.CategoriesHash['TRANSPORTATION']
@@ -170,6 +171,8 @@ local function PostProcessUnit(unit)
     local isTech2 = unit.CategoriesHash['TECH2']
     local isTech3 = unit.CategoriesHash['TECH3']
     local isExperimental = unit.CategoriesHash['EXPERIMENTAL']
+    local isACU = unit.CategoriesHash['COMMAND']
+    local isSACU = unit.CategoriesHash['SUBCOMMANDER']
 
     -- do not touch guard scan radius values of engineer-like units, as it is the reason we have
     -- the factory-reclaim-bug that we're keen in keeping that at this point
@@ -543,6 +546,27 @@ local function PostProcessUnit(unit)
         unit.Interface.HelpText = unit.Description or "" --[[@as string]]
     end
 
+    -- Define a specific TransportSpeedReduction for all land and naval units.
+    -- Experimentals have a TransportSpeedReduction of 1 due to transports gaining 1 speed and some survival maps loading experimentals into transports.
+    -- Naval units also gain a TransportSpeedReduction of 1 to ensure mod compatibility.
+    if not unit.Physics.TransportSpeedReduction and not isStructure then    
+        if isLand and isTech1 then
+            unit.Physics.TransportSpeedReduction = 0.15
+        elseif isLand and isTech2 then
+            unit.Physics.TransportSpeedReduction = 0.3
+        elseif isSACU then
+            unit.Physics.TransportSpeedReduction = 1
+        elseif isLand and isTech3 then
+            unit.Physics.TransportSpeedReduction = 0.6
+        elseif isLand and isExperimental then
+            unit.Physics.TransportSpeedReduction = 1
+        elseif isACU then
+            unit.Physics.TransportSpeedReduction = 1
+        elseif isNaval then
+            unit.Physics.TransportSpeedReduction = 1
+        end
+    end
+
     ---------------------------------------------------------------------------
     --#region (Re) apply the ability to land on water
 

lua/ui/game/unitviewDetail.lua

@@ -722,6 +722,14 @@ function WrapAndPlaceText(bp, builder, descID, control)
             table.insert(lines, LOCF("<LOC uvd_0012>Speed: %0.1f, Reverse: %0.1f, Acceleration: %0.1f, Turning: %d",
                 bp.Physics.MaxSpeed, bp.Physics.MaxSpeedReverse, bp.Physics.MaxAcceleration, bp.Physics.TurnRate))
         end
+
+        -- Display the TransportSpeedReduction stat in the UI.
+        -- Naval units and land experimentals also have this stat, but it since it is not relevant for non-modded games, we do not display it by default.
+        -- If a mod wants to display this stat for naval units or experimentals, this file can be hooked.
+        if bp.Physics.TransportSpeedReduction and not (bp.CategoriesHash.NAVAL or bp.CategoriesHash.EXPERIMENTAL) then
+            table.insert(lines, LOCF("<LOC uvd_0017>Transport Speed Reduction: %.3g",
+            bp.Physics.TransportSpeedReduction))
+        end
 
         table.insert(blocks, {color = 'FFB0FFB0', lines = lines})
     end

units/UAA0104/UAA0104_unit.bp

@@ -21,7 +21,7 @@ UnitBlueprint{
         KTurn = 2,
         KTurnDamping = 2,
         LiftFactor = 8,
-        MaxAirspeed = 13.5,
+        MaxAirspeed = 14.5,
         StartTurnDistance = 10,
         TransportHoverHeight = 4,
     },

units/UAA0107/UAA0107_unit.bp

@@ -21,7 +21,7 @@ UnitBlueprint{
         KTurn = 2,
         KTurnDamping = 2,
         LiftFactor = 8,
-        MaxAirspeed = 10,
+        MaxAirspeed = 10.75,
         StartTurnDistance = 10,
         TransportHoverHeight = 4,
     },

units/UEA0104/UEA0104_unit.bp

@@ -21,7 +21,7 @@ UnitBlueprint{
         KTurn = 2,
         KTurnDamping = 2,
         LiftFactor = 8,
-        MaxAirspeed = 13.5,
+        MaxAirspeed = 14.5,
         StartTurnDistance = 10,
         TransportHoverHeight = 4,
     },

units/UEA0107/UEA0107_unit.bp

@@ -21,7 +21,7 @@ UnitBlueprint{
         KTurn = 2,
         KTurnDamping = 2,
         LiftFactor = 8,
-        MaxAirspeed = 10,
+        MaxAirspeed = 10.75,
         StartTurnDistance = 10,
         TransportHoverHeight = 4,
     },

units/URA0104/URA0104_unit.bp

@@ -21,7 +21,7 @@ UnitBlueprint{
         KTurn = 2,
         KTurnDamping = 2,
         LiftFactor = 8,
-        MaxAirspeed = 13.5,
+        MaxAirspeed = 14.5,
         StartTurnDistance = 10,
         TransportHoverHeight = 4,
     },

units/URA0107/URA0107_unit.bp

@@ -21,7 +21,7 @@ UnitBlueprint{
         KTurn = 2,
         KTurnDamping = 2,
         LiftFactor = 8,
-        MaxAirspeed = 10,
+        MaxAirspeed = 10.75,
         StartTurnDistance = 10,
         TransportHoverHeight = 4,
     },

units/XEA0306/XEA0306_unit.bp

@@ -22,7 +22,7 @@ UnitBlueprint{
         KTurn = 2,
         KTurnDamping = 2,
         LiftFactor = 7,
-        MaxAirspeed = 15,
+        MaxAirspeed = 17.5,
         StartTurnDistance = 10,
         TransportHoverHeight = 6,
     },

units/XSA0104/XSA0104_unit.bp

@@ -21,7 +21,7 @@ UnitBlueprint{
         KTurn = 2,
         KTurnDamping = 4,
         LiftFactor = 8,
-        MaxAirspeed = 13.5,
+        MaxAirspeed = 14.5,
         StartTurnDistance = 10,
         TransportHoverHeight = 4,
     },

units/XSA0107/XSA0107_unit.bp

@@ -21,7 +21,7 @@ UnitBlueprint{
         KTurn = 2,
         KTurnDamping = 2,
         LiftFactor = 8,
-        MaxAirspeed = 10,
+        MaxAirspeed = 10.75,
         StartTurnDistance = 10,
         TransportHoverHeight = 4,
     },