C4 Engine
Bitsquid is a new high-end game engine, built from the ground up to focus on excellent multicore performance, cache friendly data layouts and advanced rendering techniques.
Unity is a game development ecosystem: a powerful rendering engine fully integrated with a complete set of intuitive tools and rapid workflows to create interactive 3D and 2D content; easy multiplatform publishing; thousands of quality, ready-made assets in the Asset Store and a knowledge-sharing community.
Hero Engine
Unreal Engine
Ogre (MIT License)
OctaForge is, among other things, a 3D Game Engine, with Lua scripting and an easy to use in-game editor. (MIT/BSD-style license)
Torque3D MIT Licensed Open Source version of Torque 3D from GarageGames. Documentation. See also: GarageGames - It's here! The MIT licensed Torque 3D GitHub repo is ready!
Godot is a fully featured, open source, MIT licensed, game engine. It focuses on having great tools, and a visual oriented workflow that can export to PC, Mobile and Web platforms with no hassle. The editor, language and APIs are feature rich, yet simple to learn, allowing you to become productive in a matter of hours. Godot GitHub page
OpenSceneGraph is an open source high performance 3D graphics toolkit, used by application developers in fields such as visual simulation, games, virtual reality, scientific visualization and modelling. Written entirely in Standard C++ and OpenGL it runs on all Windows platforms, OSX, GNU/Linux, IRIX, Solaris, HP-Ux, AIX and FreeBSD operating systems. (OpenSceneGraph Public License)
LWJGL is a Java library that enables cross-platform access to popular native APIs useful in the development of graphics (OpenGL), audio (OpenAL) and parallel computing (OpenCL) applications. This access is direct and high-performance, yet also wrapped in a type-safe and user-friendly layer, appropriate for the Java ecosystem. LWJGL is an enabling technology and provides low-level access. It is not a framework and does not provide higher-level utilities than what the native libraries expose. As such, novice programmers are encouraged to try one of the frameworks or game engines that make use of LWJGL, before working directly with the library. (BSD license)
Horde3D s a small open source 3D rendering engine. It is written in an effort to create a graphics engine that offers the stunning visual effects expected in next-generation games while at the same time being as lightweight and conceptually clean as possible. Horde3D has a simple and intuitive interface accessible from virtually any programming language and is particularly suitable for rendering large crowds of animated characters in next-generation quality. Licensed under the Eclipse Public License v1.0 (EPL).
Urho3D is a free lightweight, cross-platform 2D and 3D game engine implemented in C++ and released under the MIT license. Greatly inspired by OGRE and Horde3D. License: MIT.
Atomic Game Engine s a powerful game authoring solution which features cross platform editing and deployment to Windows, OSX, Android, iOS, Linux, and WebGL. Games and other applications can be written in JavaScript, TypeScript, C++, with C# scripting in the works. License: MIT.
Irrlicht Engine is an open source high performance realtime 3D engine written in C++. It is completely cross-platform, using D3D, OpenGL and its own software renderers, and has all of the state-of-the-art features which can be found in commercial 3d engines. License: The Irrlicht Engine License based on the zlib/libpng license with the name and the authors name replaced.
The G3D Innovation Engine is a commercial-grade C++ 3D engine available as Open Source (BSD License). It is used in commercial games, research papers, military simulators, and university courses. G3D supports hardware accelerated real-time rendering, off-line rendering like ray tracing, and general purpose computation on GPUs.
Open 3D Engine The O3DE is an open-source, cross-platform, real time 3D engine that you can use to create high performance interactive experiences, including games and simulations.