Open source for video games

Abstract

Open-source software is a relevant topic in video game development. Taking a look at the most frequently employed game engines for developing Android games [1] we can see that seven out of ten ranked engines are OSS. Over the last decade, more and more game studios and individual developers switched to open-source software. Oliver Franzke from Double Fine Productions described the phenomenon from his point of view at GDC Europe 2013 [2]. For him developing game engines from scratch is too costly, and re-using self-made game engines often involves too much repurposing as they were developed with one specific game in mind. Existing third-party game engines might not support all features needed, and requesting new features or APIs from the developers is a tedious effort. In contrast to that, an open-source game engine is typically stable, extendable, and - in the best case - has a lively community accepting patches and helping out problems. Best of all, if a bug in the game engine is found or a feature is needed, one can fix it and compile it instead of filing a bug report or feature request and hoping for the next release of the engine being in time for the release of the own project. Epic Games was one of the first AAA game engine developers to publish the source code of their Unreal Engine [3] in 2015 to let game developers investigate critical parts and send in patches and file bug reports. However, they did not change their model to OSS. Amazon (with the Lumberyard engine), Unity, and Crytek (with the CryEngine) follow similar models, where the source code is available for developers, but no open-source license is used. Other prominent source code releases included the famous id Tech engines, which powered games like Doom and Quake, and the Serious Sam Engine from Croteam [4, 5]. In both cases, they were made available GPL license for historical and educational purposes and developers never released the most recent version of their engines. These engines are not used only to develop games, but also to implement simulators that can be used to create datasets used in research, like CARLA [19] (a simulator for autonomous driving research) or UnrealCV [20], that are both based on Unreal Engine.