Change: Experimental pressure distribution algorithm

https://bveworldwide.forumotion.com/t2411-no-matter-what-i-do-the-speed-at-which-the-automatic-air-brake-engages-disengages-does-not-change#21824

Author: leezer3

source/CarXMLConvertor/Convert.ExtensionsCfg.cs

@@ -572,6 +572,7 @@ internal static void GenerateCarXML(ref TabbedList newLines, int i)
 			newLines.Add("<EmergencyRate>" + ConvertTrainDat.BrakeCylinderEmergencyRate + "</EmergencyRate>");
 			newLines.Add("<ReleaseRate>" + ConvertTrainDat.BrakeCylinderReleaseRate + "</ReleaseRate>");
 			newLines.Add("</BrakeCylinder>");
+			newLines.Add("<LegacyPressureDistribution>true</LegacyPressureDistribution>");
 			newLines.Add("</Brake>");
 			newLines.Add("<Doors>");
 			newLines.Add("<Width>" + ConvertTrainDat.DoorWidth / 1000.0 + "</Width>");

source/Plugins/Train.OpenBve/Train/BVE/TrainDatParser.cs

@@ -231,6 +231,7 @@ internal void Parse(string FileName, Encoding Encoding, TrainBase Train) {
 			ReadhesionDeviceType ReAdhesionDevice = ReadhesionDeviceType.TypeA;
 			PassAlarmType passAlarm = PassAlarmType.None;
 			Train.Handles.HasLocoBrake = false;
+			Train.Specs.AveragesPressureDistribution = true;
 			double[] powerDelayUp = { }, powerDelayDown = { }, brakeDelayUp = { }, brakeDelayDown = { }, locoBrakeDelayUp = { }, locoBrakeDelayDown = { };
 			double electricBrakeDelayUp = 0, electricBrakeDelayDown = 0;
 			int powerNotches = 0, brakeNotches = 0, locoBrakeNotches = 0, powerReduceSteps = -1, locoBrakeType = 0, driverPowerNotches = 0, driverBrakeNotches = 0;

source/Plugins/Train.OpenBve/Train/XML/TrainXmlParser.BrakeNode.cs

@@ -230,6 +230,16 @@ private void ParseBrakeNode(XmlNode Node, string fileName, int Car, ref TrainBas
 					case "handle":
 						ParseHandleNode(c, ref Train.Handles.Brake, Car, Train, fileName);
 						break;
+					case "legacypressuredistribution":
+						if (c.InnerText == "1" || c.InnerText.ToLowerInvariant() == "true")
+						{
+							Train.Specs.AveragesPressureDistribution = true;
+						}
+						else
+						{
+							Train.Specs.AveragesPressureDistribution = false;
+						}
+						break;
 
 				}
 			}

source/TrainManager/Train/BrakeSystem.cs

@@ -6,6 +6,8 @@ namespace TrainManager.Trains
 {
 	public partial class TrainBase
 	{
+
+		
 		/// <summary>Updates the brake system for the entire train</summary>
 		/// <param name="TimeElapsed">The frame time elapsed</param>
 		/// <param name="DecelerationDueToBrake">An array containing the deceleration figures generated by the brake system of each car in the train</param>
@@ -20,41 +22,94 @@ public void UpdateBrakeSystem(double TimeElapsed, out double[] DecelerationDueTo
 				UpdateBrakeSystem(i, TimeElapsed, out DecelerationDueToBrake[i], out DecelerationDueToMotor[i]);
 			}
 
-			// brake pipe pressure distribution dummy (just averages)
-			double TotalPressure = 0.0;
-			for (int i = 0; i < Cars.Length; i++)
+			if (Specs.AveragesPressureDistribution)
 			{
-				if (i > 0)
+				// brake pipe pressure distribution dummy (just averages)
+				double TotalPressure = 0.0;
+				for (int i = 0; i < Cars.Length; i++)
 				{
-					if (Cars[i - 1].Derailed | Cars[i].Derailed)
+					if (i > 0)
 					{
-						Cars[i].CarBrake.brakePipe.CurrentPressure -= Cars[i].CarBrake.brakePipe.LeakRate * TimeElapsed;
-						if (Cars[i].CarBrake.brakePipe.CurrentPressure < 0.0) Cars[i].CarBrake.brakePipe.CurrentPressure = 0.0;
+						if (Cars[i - 1].Derailed | Cars[i].Derailed)
+						{
+							Cars[i].CarBrake.brakePipe.CurrentPressure -= Cars[i].CarBrake.brakePipe.LeakRate * TimeElapsed;
+							if (Cars[i].CarBrake.brakePipe.CurrentPressure < 0.0) Cars[i].CarBrake.brakePipe.CurrentPressure = 0.0;
+						}
 					}
-				}
 
-				if (i < Cars.Length - 1)
-				{
-					if (Cars[i].Derailed | Cars[i + 1].Derailed)
+					if (i < Cars.Length - 1)
 					{
-						Cars[i].CarBrake.brakePipe.CurrentPressure -= Cars[i].CarBrake.brakePipe.LeakRate * TimeElapsed;
-						if (Cars[i].CarBrake.brakePipe.CurrentPressure < 0.0) Cars[i].CarBrake.brakePipe.CurrentPressure = 0.0;
+						if (Cars[i].Derailed | Cars[i + 1].Derailed)
+						{
+							Cars[i].CarBrake.brakePipe.CurrentPressure -= Cars[i].CarBrake.brakePipe.LeakRate * TimeElapsed;
+							if (Cars[i].CarBrake.brakePipe.CurrentPressure < 0.0) Cars[i].CarBrake.brakePipe.CurrentPressure = 0.0;
+						}
 					}
+
+					TotalPressure += Cars[i].CarBrake.brakePipe.CurrentPressure;
 				}
 
-				TotalPressure += Cars[i].CarBrake.brakePipe.CurrentPressure;
+				double averagePressure = TotalPressure / Cars.Length;
+				for (int i = 0; i < Cars.Length; i++)
+				{
+					Cars[i].CarBrake.brakePipe.CurrentPressure = averagePressure;
+				}
 			}
-
-			double AveragePressure = TotalPressure / Cars.Length;
-			for (int i = 0; i < Cars.Length; i++)
+			else
 			{
-				Cars[i].CarBrake.brakePipe.CurrentPressure = AveragePressure;
+
+				/*
+				 * Notes:
+				 * This algorithm will have a 1 frame (~10ms at 100fps) delay
+				 * in pressure changes rippling down the pipe
+				 *
+				 * For the minute (subject to change), assuming that the charge rate is
+				 * the total from *both* ends of the pipe, so divide by 2
+				 *
+				 */
+
+				int lastMainBrake = 0;
+				for (int i = 0; i < Cars.Length; i++)
+				{
+					Cars[i].CarBrake.brakePipe.CurrentPressure -= Cars[i].CarBrake.brakePipe.LeakRate * TimeElapsed;
+					if (Cars[i].CarBrake.brakePipe.CurrentPressure < 0.0) Cars[i].CarBrake.brakePipe.CurrentPressure = 0.0;
+					if (Cars[i].CarBrake.brakeType == BrakeType.Main)
+					{
+						// If at the end of the train or a compressor we don't need to flow into it
+						bool nextCarIsMainBrake = i == Cars.Length || Cars[i + 1].CarBrake.brakeType == BrakeType.Main;
+						
+						if (i > 0)
+						{
+							// Back flow
+							for (int j = i; j > lastMainBrake; j--)
+							{
+								double pressureChange = Math.Min(Cars[j].CarBrake.brakePipe.NormalPressure - Cars[j].CarBrake.brakePipe.CurrentPressure, Cars[j].CarBrake.brakePipe.ChargeRate / 2) * TimeElapsed;
+								double pressureDiff = Math.Min(pressureChange, Cars[j].CarBrake.brakePipe.CurrentPressure) * TimeElapsed;
+								Cars[i].CarBrake.brakePipe.CurrentPressure -= pressureDiff;
+								Cars[j].CarBrake.brakePipe.CurrentPressure += pressureDiff;
+							}
+						}
+						// Forwards flow
+						for (int j = i; j < Cars.Length; j++)
+						{
+							double pressureChange = Math.Min(Cars[j].CarBrake.brakePipe.NormalPressure - Cars[j].CarBrake.brakePipe.CurrentPressure, Cars[j].CarBrake.brakePipe.ChargeRate / 2) * TimeElapsed;
+							double pressureDiff = Math.Min(pressureChange, Cars[j].CarBrake.brakePipe.CurrentPressure) * TimeElapsed;
+							Cars[i].CarBrake.brakePipe.CurrentPressure -= pressureDiff;
+							Cars[j].CarBrake.brakePipe.CurrentPressure += pressureDiff;
+							if (nextCarIsMainBrake)
+							{
+								break;
+							}
+						}
+						lastMainBrake = i;
+					}
+				}
 			}
 		}
 
 		/// <summary>Updates the brake system for a car within this train</summary>
 		/// <remarks>This must remain a property of the train, for easy access to various base properties</remarks>
-		/// <param name="CarIndex">The induvidual car</param>
+		/// <param name="CarIndex">The individual car</param>
 		/// <param name="TimeElapsed">The frame time elapsed</param>
 		/// <param name="DecelerationDueToBrake">The total brake deceleration this car provides</param>
 		/// <param name="DecelerationDueToMotor">The total motor deceleration this car provides</param>

source/TrainManager/Train/TrainSpecs.cs

@@ -20,5 +20,7 @@ public struct TrainSpecs
 		public DoorMode DoorCloseMode;
 		/// <summary>Whether door closure has been attempted</summary>
 		public bool DoorClosureAttempted;
+		/// <summary>Whether the pressure distribution uses the legacy averages algorithm</summary>
+		public bool AveragesPressureDistribution;
 	}
 }