fix: Bepu and InputSystem update order (#2848)

Author: Eideren

sources/engine/Stride.BepuPhysics/Stride.BepuPhysics/Definitions/SystemsOrderHelper.cs

@@ -1,19 +1,23 @@
 // Copyright (c) .NET Foundation and Contributors (https://dotnetfoundation.org/ & https://stride3d.net)
 // Distributed under the MIT license. See the LICENSE.md file in the project root for more information.
 
+using Stride.Engine;
 using Stride.Engine.Processors;
 
 namespace Stride.BepuPhysics.Definitions;
 
 internal static class SystemsOrderHelper
 {
-
     //Note : transform processor's Draw() is at -200;
 
     /// <summary> Creation and management of constraints </summary>
     public const int ORDER_OF_CONSTRAINT_P = -900;
-    /// <summary> Simulation Step(dt) & Transform Update() </summary>
-    public const int ORDER_OF_GAME_SYSTEM = int.MaxValue;
+    /// <summary> Simulation Step(dt) & Transform Update()</summary>
+    /// <remarks>
+    /// Must happen before <see cref="ScriptSystem.Update"/> to make sure interpolated bodies update their positions before users read them,
+    /// but after <see cref="InputSystem.Update"/> otherwise users would be reading last frame's input in <see cref="Components.ISimulationUpdate"/>
+    /// </remarks>
+    public const int ORDER_OF_GAME_SYSTEM = InputSystem.DefaultUpdateOrder + 1;
     /// <summary> Drawing debug wireframe, must occur after <see cref="TransformProcessor.Draw"/> </summary>
     public const int ORDER_OF_DEBUG_P = 1000;
     /// <summary> Creation and management of collidable, rebuilds static meshes when they are moved, must occur after <see cref="TransformProcessor.Draw"/> </summary>

sources/engine/Stride.Engine/Engine/InputSystem.cs

@@ -13,10 +13,13 @@ namespace Stride.Engine
     /// </summary>
     public sealed class InputSystem : GameSystemBase
     {
+        public const int DefaultUpdateOrder = -50;
+        
         public InputSystem(IServiceRegistry registry) : base(registry)
         {
             Enabled = true;
             Manager = new InputManager().DisposeBy(this);
+            UpdateOrder = DefaultUpdateOrder;
         }
 
         public InputManager Manager { get; }