The emergence of cheaper technologies for immersive environments has considerably increased the interest in Virtual Reality applications. However, VR frameworks currently available force user applications to be developed specifically for them. This increases the cost of converting an existing application to another virtual reality environment. This paper proposes a new framework, the LVRL (Lightweight Virtual Reality Libraries), which allows the creation or conversion of existing applications to VR without changing the application's structure. The LVRL's main objective is to provide a nonintrusive and transparent programming interface that allows the development of VR applications by non-VR developers. This paper describes LVRL's architecture, features, usage, and benefits obtained by applications using it.