OpenEngine hosts the .NET CoreCLR to enable C# scripting for game logic. The scripting system supports hot-reloading, asset interaction, and bidirectional C++/C# interop.

How It Works

C# Script (Assets/Scripts/*.cs)
    ↓
CoreCLR Host (in engine)
    ↓
C++ ↔ C# P/Invoke Interop
    ↓
Engine Systems (rendering, physics, assets)

The engine initializes CoreCLR at startup, loads compiled assemblies from build/bin/<Config>/ScriptAssemblies/, and invokes C# entry points each frame.

Script Assembly Pipeline

1. Place .cs files in Assets/
2. Build the C++ project — CMake generates OpenEngine.Scripts.csproj and builds it
3. Output: build/bin/<Config>/ScriptAssemblies/OpenEngine.Scripts.dll
4. Engine loads the assembly at runtime

No manual dotnet build needed — the ScriptAssemblies pipeline is part of the CMake build.

C++ to C# Interop

The engine registers native functions that C# can call via P/Invoke:

// NativeInterop.cs — provided by the engine
public static class NativeInterop
{
    [DllImport("Engine")]
    public static extern void LogMessage(string message);

    [DllImport("Engine")]
    public static extern int GetAssetCount();

    [DllImport("Engine")]
    public static extern int AddNumbers(int a, int b);
}

Hot-Reloading

The engine monitors Assets/ for file changes using platform-native file watchers:

• Windows: ReadDirectoryChangesW API
• Linux/macOS: inotify / FSEvents

When a .cs file changes, the engine recompiles the assembly and reloads it — no restart required.

Lifecycle

1. OnInitialize() — called once at startup
2. OnUpdate(float deltaTime) — called every frame
3. OnShutdown() — called during engine shutdown
4. [InitializeOnLoad] — attribute for editor-time initialization

Next Steps

• Build the Editor to use the visual tooling
• Follow the Development Workflow for scripting sessions