Added a scene to experiment with split-screen running multiple instances of the game. Added the ability to override the default engine library name, and added additional layers for camera masking.

Assets/Scenes/SplitScreenTest.unity.meta

@@ -0,0 +1,7 @@
+fileFormatVersion: 2
+guid: 4ca6e7235b69a0d4dbe7cadc2b23fb6e
+DefaultImporter:
+  externalObjects: {}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

Assets/Scripts/Layers.cs

@@ -2,6 +2,15 @@
 {
     Game1 = 6,
     ViewModel1 = 7,
+    
+    Game2 = 9,
+    ViewModel2 = 10,
+    
+    Game3 = 12,
+    ViewModel3 = 13,
+    
+    Game4 = 15,
+    ViewModel4 = 16,
 }
 
 public static class LayerExtensions

Assets/Scripts/SplitScreenTest.cs

@@ -0,0 +1,63 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+
+public class SplitScreenTest : MonoBehaviour
+{
+    [SerializeField]
+    private GameInstance[] gameInstances = new GameInstance[4];
+
+    [SerializeField]
+    private List<VisualStyle> visualStyles = new List<VisualStyle>();
+    
+    private void Start()
+    {
+        Debug.Log($"Running in {IntPtr.Size * 8}-bit mode");
+
+        Layers gameLayer = Layers.Game1;
+        Layers viewLayer = Layers.ViewModel1;
+        int layerStride = Layers.Game2 - Layers.Game1;
+        
+        foreach (var gameInstance in gameInstances)
+        {
+            if (gameInstance == null || gameInstance.mainCamera == null)
+                continue;
+            
+            var uq = gameObject.AddComponent<UniQuake>();
+            uq.BaseGame = gameInstance.baseGame;
+            uq.ModDirectory = gameInstance.modPath;
+            uq.AdditionalArguments = ParseArgs(gameInstance.arguments);
+            uq.Camera = gameInstance.mainCamera;
+            uq.GameLayer = gameLayer;
+            uq.ViewModelLayer = viewLayer;
+            uq.LibraryOverride = gameInstance.libraryName;
+            uq.SetVisualStyle(visualStyles[0]);
+
+            gameLayer += layerStride;
+            viewLayer += layerStride;
+        }
+    }
+
+    private string[] ParseArgs(string args)
+    {
+        if (args == null)
+            return new string[0];
+        
+        return args.Split(new[] {' ', '\t', '\r', '\n'}, StringSplitOptions.RemoveEmptyEntries);
+    }
+
+    [Serializable]
+    public class GameInstance
+    {
+        public Camera mainCamera;
+
+        public MissionPack baseGame;
+
+        public string modPath;
+
+        public string arguments;
+
+        public string libraryName;
+    }
+}

Assets/Scripts/SplitScreenTest.cs.meta

@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: 47d8bb9d10da63c4d9b96cb96a94aca3
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

Assets/Scripts/UniQuake.Interop.cs

@@ -38,11 +38,12 @@ public partial class UniQuake
         string dllFile = Path.Combine(Application.dataPath, DllPath);
 
         // Experimental code to allow running multiple instances of Quake next to each other
-        // string dllName = Path.GetFileNameWithoutExtension(dllFile);
-        // string dllExt = Path.GetExtension(dllFile);
-        // string dllCopy = Path.Combine(Application.persistentDataPath, $"{dllName}{GetInstanceID()}{dllExt}");
-        // File.Copy(dllFile, dllCopy, true);
-        // dllFile = dllCopy;
+        if (!string.IsNullOrEmpty(LibraryOverride))
+        {
+            string directory = Path.GetDirectoryName(dllFile);
+            string extension = Path.GetExtension(dllFile);
+            dllFile = Path.Combine(directory, LibraryOverride + extension);
+        }
         
         libraryHandle = SystemLibrary.LoadLibrary(dllFile);
         if (libraryHandle == IntPtr.Zero)

Assets/Scripts/UniQuake.cs

@@ -28,6 +28,8 @@ public partial class UniQuake: MonoBehaviour
     public string ModDirectory { get; set; }
     public string[] AdditionalArguments { get; set; }
     
+    public string LibraryOverride { get; set; }
+    
     /// <summary>
     /// Time since startup for this particular instance of Quake
     /// </summary>

ProjectSettings/TagManager.asset

@@ -14,14 +14,14 @@ TagManager:
   - Game1
   - ViewModel1
   - 
+  - Game2
+  - ViewModel2
   - 
+  - Game3
+  - ViewModel3
   - 
-  - 
-  - 
-  - 
-  - 
-  - 
-  - 
+  - Game4
+  - ViewModel4
   - 
   - 
   -