Make passive gates great (#9816)

Content.Server/Atmos/Piping/Binary/Components/GasPassiveGateComponent.cs

@@ -5,17 +5,6 @@ namespace Content.Server.Atmos.Piping.Binary.Components
     [RegisterComponent]
     public sealed class GasPassiveGateComponent : Component
     {
-        [DataField("enabled")]
-        [ViewVariables(VVAccess.ReadWrite)]
-        public bool Enabled { get; set; } = true;
-
-        /// <summary>
-        ///     This is the minimum difference needed to overcome the friction in the mechanism.
-        /// </summary>
-        [ViewVariables(VVAccess.ReadWrite)]
-        [DataField("frictionDifference")]
-        public float FrictionPressureDifference { get; set; } = 10f;
-
         [ViewVariables(VVAccess.ReadWrite)]
         [DataField("inlet")]
         public string InletName { get; set; } = "inlet";
@@ -24,8 +13,8 @@ namespace Content.Server.Atmos.Piping.Binary.Components
         [DataField("outlet")]
         public string OutletName { get; set; } = "outlet";
 
-        [ViewVariables(VVAccess.ReadWrite)]
+        [ViewVariables(VVAccess.ReadOnly)]
-        [DataField("targetPressure")]
+        [DataField("flowRate")]
-        public float TargetPressure { get; set; } = Atmospherics.OneAtmosphere;
+        public float FlowRate { get; set; } = 0;
     }
 }

Content.Server/Atmos/Piping/Binary/EntitySystems/GasPassiveGateSystem.cs

@@ -4,6 +4,7 @@ using Content.Server.Atmos.Piping.Components;
 using Content.Server.NodeContainer;
 using Content.Server.NodeContainer.Nodes;
 using Content.Shared.Atmos;
+using Content.Shared.Examine;
 using JetBrains.Annotations;
 
 namespace Content.Server.Atmos.Piping.Binary.EntitySystems
@@ -12,19 +13,18 @@ namespace Content.Server.Atmos.Piping.Binary.EntitySystems
     public sealed class GasPassiveGateSystem : EntitySystem
     {
         [Dependency] private readonly AtmosphereSystem _atmosphereSystem = default!;
+        [Dependency] private readonly ExamineSystemShared _examineSystem = default!;
 
         public override void Initialize()
         {
             base.Initialize();
 
             SubscribeLocalEvent<GasPassiveGateComponent, AtmosDeviceUpdateEvent>(OnPassiveGateUpdated);
+            SubscribeLocalEvent<GasPassiveGateComponent, ExaminedEvent>(OnExamined);
         }
 
         private void OnPassiveGateUpdated(EntityUid uid, GasPassiveGateComponent gate, AtmosDeviceUpdateEvent args)
         {
-            if (!gate.Enabled)
-                return;
-
             if (!EntityManager.TryGetComponent(uid, out NodeContainerComponent? nodeContainer))
                 return;
 
@@ -32,23 +32,59 @@ namespace Content.Server.Atmos.Piping.Binary.EntitySystems
                 || !nodeContainer.TryGetNode(gate.OutletName, out PipeNode? outlet))
                 return;
 
-            var outputStartingPressure = outlet.Air.Pressure;
+            var n1 = inlet.Air.TotalMoles;
-            var inputStartingPressure = inlet.Air.Pressure;
+            var n2 = outlet.Air.TotalMoles;
+            var P1 = inlet.Air.Pressure;
+            var P2 = outlet.Air.Pressure;
+            var V1 = inlet.Air.Volume;
+            var V2 = outlet.Air.Volume;
+            var T1 = inlet.Air.Temperature;
+            var T2 = outlet.Air.Temperature;
+            var pressureDelta = P1 - P2;
 
-            if (outputStartingPressure >= MathF.Min(gate.TargetPressure, inputStartingPressure - gate.FrictionPressureDifference))
+            float dt = 1/_atmosphereSystem.AtmosTickRate;
-                return; // No need to pump gas, target reached or input pressure too low.
+            float dV = 0;
+            var denom = (T1*V2 + T2*V1);
 
-            if (inlet.Air.TotalMoles > 0 && inlet.Air.Temperature > 0)
+            if (pressureDelta > 0 && P1 > 0 && denom > 0)
             {
-                // We calculate the necessary moles to transfer using our good ol' friend PV=nRT.
+                // Calculate the number of moles to transfer to equalize the final pressure of
-                var pressureDelta = MathF.Min(gate.TargetPressure - outputStartingPressure, (inputStartingPressure - outputStartingPressure)/2);
+                // both sides of the valve. You can derive this equation yourself by solving
-                // We can't have a pressure delta that would cause outlet pressure > inlet pressure.
+                // the equations:
+                //
+                //    P_inlet,final = P_outlet,final (pressure equilibrium)
+                //    n_inlet,initial + n_outlet,initial = n_inlet,final + n_outlet,final (mass conservation)
+                //
+                // These simplifying assumptions allow an easy closed-form solution:
+                //
+                //    T_inlet,initial = T_inlet,final
+                //    T_outlet,initial = T_outlet,final
+                //
+                // If you don't want to push through the math, just know that this behaves like a
+                // pump that can equalize pressure instantly, i.e. much faster than pressure or
+                // volume pumps.
+                var transferMoles = n1 - (n1+n2)*T2*V1 / denom;
 
-                var transferMoles = pressureDelta * outlet.Air.Volume / (inlet.Air.Temperature * Atmospherics.R);
+                // Get the volume transfered to update our flow meter.
+                dV = n1*Atmospherics.R*T1/P1;
 
                 // Actually transfer the gas.
                 _atmosphereSystem.Merge(outlet.Air, inlet.Air.Remove(transferMoles));
             }
+
+            // Update transfer rate with an exponential moving average.
+            var tau = 1;    // Time constant (averaging time) in seconds
+            var a = dt/tau;
+            gate.FlowRate = a*dV/tau + (1-a)*gate.FlowRate; // in L/sec
+        }
+
+        private void OnExamined(EntityUid uid, GasPassiveGateComponent gate, ExaminedEvent args)
+        {
+            if (!EntityManager.GetComponent<TransformComponent>(gate.Owner).Anchored || !args.IsInDetailsRange) // Not anchored? Out of range? No status.
+                return;
+
+            var str = Loc.GetString("gas-passive-gate-examined", ("flowRate", $"{gate.FlowRate:0.#}"));
+            args.PushMarkup(str);
         }
     }
 }

Resources/Locale/en-US/atmos/gas-passive-gate-component.ftl

@@ -0,0 +1 @@
+gas-passive-gate-examined = The flow rate meter indicates [color=lightblue]{$flowRate} liters/sec[/color].