Automatic merge of T1.5.1-1695-gade019506 and 17 pull requests

- Pull request #570 at f11a428: glTF 2.0 support with PBR lighting
- Pull request #900 at 4629736: DMI in 3D cab + two more dials
- Pull request #1030 at d3ae4a2: Refactor settings, in prep for settings exporter
- Pull request #1045 at cc4d53c: Bugfix: Empty Start Time for Explore, and other issues loading from Menu Selection and Content Routes
- Pull request #1052 at 5bbc476: Content Manager: Add axle count, and lowest derail force
- Pull request #1062 at de91cc4: Train Forces popup Window.
- Pull request #1064 at 9b3415e: Add Train Info tab to Help window (F1)
- Pull request #1066 at 62c89c1: Log derailment, using TraceInformation.
- Pull request #892 at 1f5ba4c: Signal Function OPP_SIG_ID_TRAINPATH
- Pull request #1000 at d8d9709: Locomotive operation from control car
- Pull request #1029 at 92c74ef: Superelevation Follow Up Fixes
- Pull request #1057 at 50c3789: Switchable brake system
- Pull request #1069 at 3f153f0: Mouse wheel control only with Alt – Followup for #1051
- Pull request #1070 at f818e40: Fix a NullReferenceException in TCS scripts
- Pull request #1055 at 5c78967: Route Based TTrack Sounds
- Pull request #896 at f1681df: First implementation of https://blueprints.launchpad.net/or/+spec/specific-sounds-for-ai-trains
- Pull request #1049 at 4dd8c4f: Re-organise document storage and access

Author: openrails-bot

Diff for: Source/RunActivity/Content/SceneryShader.fx

@@ -85,7 +85,7 @@ int      MorphConfig[9]; // 0-5: position of POSITION, NORMAL, TANGENT, TEXCOORD
 float    MorphWeights[MAX_MORPH_TARGETS]; // the actual morphing animation state
 
 int		NumLights; // The number of the lights used
-float	LightTypes[MAX_LIGHTS]; // 0: directional, 1: point, 2: spot
+float	LightTypes[MAX_LIGHTS]; // 0: directional, 1: point, 2: spot, 3: headlight
 float3	LightPositions[MAX_LIGHTS];
 float3	LightDirections[MAX_LIGHTS];
 float3	LightColors[MAX_LIGHTS];

Diff for: Source/RunActivity/Viewer3D/Lights.cs

@@ -272,13 +272,12 @@ public void PrepareFrame(RenderFrame frame, ElapsedTime elapsedTime)
                     LightConeDirection = Vector3.Transform(Vector3.Lerp(ActiveLightCone.Direction1, ActiveLightCone.Direction2, ActiveLightCone.Fade.Y), ShapeXNATranslations[coneIndex]);
                     LightConeDirection -= ShapeXNATranslations[coneIndex].Translation;
                     LightConeDirection.Normalize();
-                    // The original shaders followed the phylisophy of wanting 50% brightness at half the range. (LightConeDistance is only the half.) Now we need the full range.
-                    LightConeDistance = 2 * MathHelper.Lerp(ActiveLightCone.Distance1, ActiveLightCone.Distance2, ActiveLightCone.Fade.Y);
+                    LightConeDistance = 4 * MathHelper.Lerp(ActiveLightCone.Distance1, ActiveLightCone.Distance2, ActiveLightCone.Fade.Y);
                     LightConeOuterAngle = MathHelper.Lerp(ActiveLightCone.Angle1, ActiveLightCone.Angle2, ActiveLightCone.Fade.Y);
                     var lightConeColor = Vector4.Lerp(ActiveLightCone.Color1, ActiveLightCone.Color2, ActiveLightCone.Fade.Y);
-                    LightConeColor = new Vector3(lightConeColor.X, lightConeColor.Y, lightConeColor.Z);
+                    LightConeColor = new Vector3(lightConeColor.X, lightConeColor.Y, lightConeColor.Z) * lightConeColor.W;
 
-                    frame.AddLight(LightMode.Spot, LightConePosition, LightConeDirection, LightConeColor, RenderFrame.HeadLightIntensity * lightConeColor.W, LightConeDistance, 0, LightConeOuterAngle, ActiveLightCone.Fade.X, false);
+                    frame.AddLight(LightMode.Headlight, LightConePosition, LightConeDirection, LightConeColor, RenderFrame.HeadLightIntensity, LightConeDistance, 0, LightConeOuterAngle, ActiveLightCone.Fade.X, false);
                 }
                 else
                 {

Diff for: Source/RunActivity/Viewer3D/RenderFrame.cs

@@ -73,7 +73,8 @@ public enum LightMode
     {
         Directional = 0,
         Point = 1,
-        Spot = 2
+        Spot = 2,
+        Headlight = 3
     }
 
     public abstract class RenderPrimitive
@@ -392,7 +393,8 @@ public class RenderFrame
         static readonly Vector3 MoonGlow = new Vector3(245f / 255f, 243f / 255f, 206f / 255f);
         const float SunIntensity = 1;
         const float MoonIntensity = SunIntensity / 380000;
-        public const float HeadLightIntensity = 250000; // See some sample values: https://docs.unity3d.com/Packages/[email protected]/manual/LightUnits.html
+        //public const float HeadLightIntensity = 250000; // See some sample values: https://docs.unity3d.com/Packages/[email protected]/manual/LightUnits.html
+        public const float HeadLightIntensity = 4; // Using the old linear attenuation model
 
         const float LIGHT_INTENSITY_ADJUSTMENT_SPOT = 1f;
         const float LIGHT_INTENSITY_ADJUSTMENT_POINT = 0.08f; // By visual inspection of PlaysetLightTest at nighttime. Probably should be 1 / 4π = 0.08