A multi-platform support c++11 library with focus on asio
Cocos simplifies game creation and distribution with Cocos Creator
Cross-platform game engine in Rust
Open source library for creative expression on the web, desktop, etc.
Real-time physically based rendering engine for Android, iOS, and more
Delphi : VRCalc++ OOSL & + (Paged List, TextEditor, VRAstroVision ...)
Accelerate cross-platform MR app development in Unity
The Atomic Game Engine is a multi-platform 2D and 3D engine
Open-source, cross-platform, C++ game engine for creating 2D/3D games
Cocos2d for iOS and OS X, built using Objective-C
Cross platform 2D/3D game engine written in C++11 & OpenGL ES 2/3
Egret is a brand new open mobile game and application engine