Godot Engine – Multi-platform 2D and 3D game engine

JSON for Modern C++

Emscripten: An LLVM-to-WebAssembly Compiler

A modern, C++-native, test framework for unit-tests, TDD and BDD - using C++14, C++17 and later (C++11 support is in v2.x branch, and C++03 on the Catch1.x branch)

A fast JSON parser/generator for C++ with both SAX/DOM style API

Flexible level editor

OpenGL Mathematics (GLM)

Industry-standard navigation-mesh toolset for games

TinyXML2 is a simple, small, efficient, C++ XML parser that can be easily integrated into other programs.

Open-source, cross-platform, C++ game engine for creating 2D/3D games.

Doom 3 GPL source release

Improved version of the X-Ray Engine, the game engine used in the world-famous S.T.A.L.K.E.R. game series by GSC Game World. Join OpenXRay! ;)

Third-person Survival Game for Unreal Engine (Sample Project)

Procedural Noise Shader Routines compatible with WebGL

Embree ray tracing kernels repository.

Polycode is a cross-platform framework for creative code.

EntityX - A fast, type-safe C++ Entity-Component system

Advanced shading language for production GI renderers

BRDF Explorer

[ARCHIVED] Modern reimplementation of the Diablo 1 game engine

A small, portable and extensible C++ 3D coding framework

Modern and efficient C++ Thread Pool Library

Horde3D is a small 3D rendering and animation engine. It is written in an effort to create an engine being as lightweight and conceptually clean as possible.

Portable header-only C++ low level SIMD library

A C++ binding for the OpenGL API, generated using the gl.xml specification.

Simple C++11 friendly header-only bindings to Lua

C++ promise/A+ library in Javascript style.

OpenGL Image (GLI)

An open source C++ entity system.

Unreal Engine smooth voxel terrain plugin