Unreal Engine 4 .NET Core integration

UnrealCLR is a plugin which natively integrates .NET Core host into the Unreal Engine with the Common Language Runtime for direct execution of the managed code through user-driven blueprint pipelines to build a game logic using the full power of .NET facilities with engine API. The project is aimed at stability, performance, and maintainability.

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Features:

• Host loading, integration, and management during the lifetime of the engine
• Dynamic loading, unloading, isolation, and dependency resolving of user assemblies at runtime
• On-the-fly access and execution of the managed functionality through blueprints
• Runtime exceptions handling and tracing
• Continuously evolving framework for access to the engine API from the managed code written in idiomatic C#
• High-performance interoperability through generated IL code and utilization of blittable data types
• Support of .NET facilities including hardware-accelerated math with transparent re-mapping to vector types of the engine
• Support of .NET tools for debugging and profiling such as JetBrains product line, dnSpy debugger, and others
• Full independence from the compilation pipeline of assemblies with support of NuGet packages, analyzers, and generators
• Automatic project packaging for standalone distribution
• Carefully handcrafted source code for best maintainability and performance
• Extensive unit testing to ensure the robustness and consistency
• Distributed as a plugin and doesn't require rebuilding the engine
• Documented source code

The plugin is available for Windows, Linux, and macOS (x64).

Building

Prerequisites

• Unreal Engine 4.25.1
• A native compilation toolchain with platform-specific dependencies
• .NET Core SDK 3.1.301

Auto

Compilation

Create a new or use an existing Unreal Engine C++ or blueprints project. Clone the repository or download a desirable version from the releases section. Navigate to Install folder, and run dotnet run command. Follow the installation instructions. Open the project after the installation process is complete.

Upgrading

To upgrade the plugin, re-run the installation process. Recompile custom code with an updated framework.

Manual

Compilation

Plugin

Create a new or use an existing Unreal Engine C++ or blueprints project. Clone the repository or download a desirable version from the releases section. Copy the content of the Source/Native folder to %Project%/Plugins/UnrealCLR directory. Compile the managed runtime from Source/Managed/Runtime folder by running the following command: dotnet publish --configuration Release --framework netcoreapp3.1 --output "%Project%/Plugins/UnrealCLR/Managed" . Restart Unreal Engine, open the project, and build the plugin.

Tests

To quickly start testing, open a project with the plugin in Unreal Engine, copy all folders from the Content of the repository to %Project%/Content directory, and wait until they loaded in the Content Browser. Compile the managed assemblies from Source/Managed/Tests folder by running the following commands:

dotnet publish "../Framework" --configuration Release --framework netcoreapp3.1
dotnet publish --configuration Release --framework netcoreapp3.1 --output "%Project%/Managed/Tests"

Upgrading

To upgrade, delete the plugin folder from a project, and repeat all steps from the compilation section. Recompile custom code with an updated framework.

Running

Plugin

The plugin is automatically loaded at startup. To make sure that it's initialized open the console window from Window -> Developer Tools -> Output Log , find UnrealCLR logs using the search input.

Tests

Open the scene with tests in the editor and enter the play mode. To switch a test, navigate to Blueprints -> Open Level Blueprint , select the Test Systems enumeration, and change default value on the right panel.

Overview

Design and architecture

UnrealCLR is designed to be flexible and extensible. The plugin is transparently managing core functionality of the runtime, binding and caching the engine API for managed environment. The programmer has full control over execution flow through blueprint pipelines that allow to dynamically weave native events of the engine and its objects with managed logic. There's no hidden states or obscured order of execution behind the lifecycle of scripts.

Assemblies management

At runtime, UnrealCLR loading managed assemblies into a cached isolated context. It allows dynamically replace assemblies after unloading them from memory, therefore the programmer can work with code without restarting the editor for continuous development. The compilation pipeline is entirely up to a developer, it can be organized in any desirable way without any limitations and with full support of NuGet packages.

Engine application program interface

The plugin and framework are evolving all the time to utilize as much power of the Unreal Engine as possible. It's crucial to have a feature-rich API. The system is created with high-performance in mind but without trading safety. The vast majority of code is written and verified by hand to prevent any unexpected behaviors at runtime and to ensure stability.

Powerful tooling

Use your favorite IDE and .NET Core tools that can be attached to the process of the engine just as to a regular .NET application for profiling and debugging. It's very convenient and works out of the box without any external effort. Analyze performance, monitor CPU usage and memory consumption, debug execution, take full control over the code. Explore new possibilities and extend your toolset in no time.

Essentials

Exceptions

The runtime redirects all unhandled exceptions to log files and on-screen messages of the engine, however, it's highly recommended to use try/catch blocks to override redirections with custom handlers. It's necessary to have an attached debugger to properly trace exceptions in the editor or standalone.

Memory management

Unreal Engine, as well as .NET runtime, utilizes a garbage collector for memory management. The framework is designed with consistency in mind to prevent crashes and validate memory transparently for a programmer, no matter how objects were created and freed: with C++, C#, or blueprints.

Hot reload

The plugin is independent of the compilation routine of user assemblies. It's loading assemblies from %Project%/Managed folder in accordance with user-driven blueprint pipelines and resolving dependencies at runtime after entering/leaving the play mode. The framework of the plugin with the engine API is automatically recognized and loaded as a dependency.

Ecosystem compatibility

The framework replicates the classes hierarchy of the engine with full interoperability support. Any external C++ code, blueprints, and plugins are compatible and extensible with UnrealCLR by design through the engine API.

Acknowledgments

Thanks to @natemcmaster for a great .NET library that simplifies dynamic loading of assemblies.

Special thanks to @Doraku for an amazing documentation generator and rapid improvement of it.