We developed OAR Converter, a conversion system to load OpenSimulator Archive (.oar) files into Unity for use in Unity-based projects. This system allows the user to load 3D world data created in OpenSimulator into Unity on a region-by-region basis, and to ultimately output the data from Unity in a variety of formats. These features allow us to treat the pairing of OpenSimulator and Unity as a shared development environment, which simplifies the low-cost creation of 3D virtual worlds.