Billy Engine

Some kind of 2D game engine, written in C++20 using OpenGL and EnTT to be used in future projects. I wanted a simple entity framework to display some graphics in my C++ applications and here it is. It is not meant to be like Unreal / Unity / Godot, the most similar thing I could find is olcPixelGameEngine and raylib. Thanks also to TheCherno for Hazel from which I took a lot of inspiration.

I've developed it in Linux for Linux but should work on other platforms as well. Windows is WIP, OSX will probably not work. I'm not targeting mobile. WASM may be interesting but definitely not a priority.

There's still a lot of work to do, check out TODO.md

It started using SDL2 for rendering but switching to OpenGL gives more customization and advanced features. Also, linking SDL2 on windows is a pain.

How to use

You can look at the code in the demo folder for now as there is no documentation and the API is really unstable.

C# Bindings are also available through SWIG. An example is available here.

In the future I might distribute a precompiled Nuget package, but for now everything has to built from scratch.

Dependencies

• OpenGL
• GLFW
• EnTT
• fmt
• glm
• spdlog
• stb_image
• Dotnet CLI (optional)
• CMake (build)
• Ninja (build, optional)
• SWIG (build, optional)
• Nuget CLI (build, optional)

Build

This repository contains the source for the engine itself that gets compiled to a dynamic library and a little demo.

cmake -S . -B build # `-G Ninja` is recommended but not required
cmake --build build

Some options that you can pass to cmake include:

• -D COMPILE_DEMO=OFF to disable the demo
• -D BUNDLE_DEPENDENCIES=OFF to get multiple DLLs for each dependency. By default they are bundled into a single DLL
• -D SYSTEM_DEPENDENCIES=ON to build the engine using packages on the system instead of downloading and compiling them (some dependencies will still be compiled because they are non-standard and usually not packaged). This works well on Linux, in particular, on Arch you would need to yay -S entt fmt glm glfw-x11 spdlog. On the other side this option is not recommended on Windows and when generating C# bindings
• -D GENERATE_BINDINGS=ON is on by default and generates C# bindings using SWIG. Can be disabled if not needed.

Additionally some convenience scripts are provided in the script folder:

• valgrind.sh runs the C++ demo through Valgrind and logs the result to valgrind.log
• cross.sh cross compiles from Linux to Windows with MinGW (experimental)
• bindings.sh generates C# bindings, projects and packages. It is recommended to run this script before using the C# demo