Vendor Lock-In in VR Game Engines: A Structured Comparison of Unity, Unreal Engine, and Godot

Game engines have become foundational platforms not only for video game development but also for Virtual Reality (VR) applications in fields such as medicine, architecture, and training. The growing dependence on a single engine throughout a project’s life cycle introduces the risk of vendor lock-in, a condition in which switching to an alternative platform becomes prohibitively costly. While partial solutions exist at the hardware level-notably the OpenXR standard-no systematic cross-engine evaluation of VR development effort and portability strategies has been established. This work presents a structured comparison of three widely adopted game engines-Unity, Unreal Engine, and Godot-through the implementation of the same VR scene in each platform. A metric called Number of Clicks (NoC) is introduced to quantify implementation effort across engines. The evaluation combines NoC measurements with qualitative analysis of architectural differences, engine-specific XR toolkits, and asset handling. In addition, practical guidelines are derived for structuring VR projects and assets so as to mitigate engine dependency.