bgfx

bgfx is a rendering library that lets you write graphics code once and run it everywhere. It sits between your game or app and the actual graphics API, Direct3D on Windows, Metal on Mac, Vulkan, OpenGL, WebGL in the browser, and handles the differences so you don't have to. The "bring your own engine" philosophy means it does rendering and nothing else: no scene graph, no physics, no asset pipeline forced on you.

There's nothing to host or pay for. You pull it into your C or C++ project as a library and build. The ops reality is the build itself: bgfx is a serious C++ codebase with its own shader compiler and toolchain, so getting it wired into your project takes real setup, not a one-line install. Once it's in, it's rock solid and has shipped in commercial games.

Solo developers and small studios who want cross-platform rendering without committing to a full engine like Unity or Unreal get exactly that here. It pairs well with your own engine code. This is not the pick if you want batteries-included game development, you'd reach for Godot or Unreal for that.

The catch: bgfx gives you a renderer, not a game. You're responsible for everything around it, and that's a lot of work if you're not already comfortable in C++ graphics land. The payoff is total control and no licensing strings, BSD-2 licensed, free forever.