EY3

OpenCV and OpenGL ES on Android, from C++ alone: no Java, no Gradle, no IDE.

EY3 is a small library for quick computer-vision and graphics experiments on a phone. You write main(); it gives you a GL context, touch events, the camera as a cv::Mat, and an APK at the end of ninja. The same code builds and runs on the desktop, which is where most of the work happens.

It is not a game engine: no sound, no text rendering, no physics, no editor. The whole API is about a dozen classes and fits in one page -- doc/ey3-api.md.

Why you might want it

• Real-time OpenCV in C++ on Android, without fighting the Android build.
• The same source running on your machine, so you can iterate without a device.
• An APK straight from a CMake target: aapt, jarsigner, zipalign.
• No Android Studio, no IDE -- it builds over SSH.

If you are writing an ordinary app with views and Material, this is the wrong tool. If you are writing a game, something like raylib will take you further.

Installing it

Java, the Android SDK and NDK, CMake, Ninja, and an OpenCV Android SDK built with objdetect and dnn; doc/environment-setup.md has every step.

./scripts/install-sdk.sh

That installs the desktop library (headers, libey3.so and an ey3Config.cmake) and, for Android, one shared copy of the engine sources and the CMake modules that build them. Everything else -- the examples below, the starter, your own projects -- is a separate project that finds ey3 that way. Nothing vendors a copy of it.

Examples

Each one is a standalone project built against the installed library, with its own README explaining what it shows and how to run it.

Example	What it shows
ey3-triangle	The smallest thing that draws: one Renderizable, a shader pair, touch input.
ey3-background-img	An image loaded from assets/ and stretched across the screen.
ey3-orb-demo	ORB feature matching on live camera frames -- the computer-vision side.
ey3-maze	A 2D maze: sprite sheets, levels read from assets/, and a structure worth copying.
ey3-maze-fishtank	The same maze in 3D under a head-coupled perspective: the front camera follows your eyes and the screen becomes a window into a box. What the library was built for.

Starting your own project

Copy templates/ey3-starter anywhere outside this repository and build it -- its README has the details. It is the same layout every example uses: your code in src/ and include/, the two entry points in desktop/ and android/, and one app.cmake both builds read.

Working on the library itself

cmake -S desktop -B build-desktop -G Ninja && cmake --build build-desktop

builds the desktop library, and the root CMakeLists.txt cross-compiles the same engine for Android, which is the check that it still builds there. Both are only for developing ey3; apps never use them directly.

Licence

EY3 is Apache 2.0 -- see LICENSE. It is built on OpenCV (https://opencv.org, Apache 2.0); doc/third-party.md lists everything it uses and what shipping a build of it involves.