okinawa

A 3D engine in C++ on top of OpenGL and GLFW, built with xmake as a static library that other projects consume from source. It takes its name, and a good part of its shape, from okinawa.js, the 2D engine in JavaScript that came ten years earlier.

What it draws

A scene graph of objects that inherit their parent’s transform, with items, groups, billboards, instanced items and sprite sheets. Five cameras come with it (fixed, inspection, spectator, third person, top down) and avatars with pluggable controllers for moving a character on the ground or panning over it.

Lighting covers clustered lights, shadow maps and a skybox, and there is a post-processing chain with bright-pass and blur stages. Meshes arrive as Wavefront OBJ files, textures through stb, and both can be loaded in the background while the frame keeps rendering. Culling is bounding sphere against frustum.

On top of the world there is a GUI layer with text, images, a console and a stats panel.

What it leaves to the application: collisions. The engine carries a minimal kinematics model (velocity, acceleration, their rotational twins) and nothing else; a collision volume is the game’s business, and it should never be derived from the triangles sent to the renderer.

An engine an agent can look at

It can start an MCP server inside the running process, listening on localhost. Through it an external agent can look at the rendered frame, inject input and read telemetry, which makes it possible to debug a visual problem without a human describing what is on screen. It is compiled in by default in debug builds, out in release ones, and still has to be switched on at runtime.

What runs on it

The engine builds a library and a test suite, nothing else: the games and tools live in their own repositories and pull it in as a dependency.

A level editor built on it, holding a city of 457 blocks at a steady 60 frames per second, with one of them selected and spinning in its own preview window.

Of those, a viewer for Doom’s level files was the first to use the engine for anything real.