The OBJ file format is an open, widely supported standard for representing 3D geometry, including vertices, texture coordinates, normals, and faces. The DFF (RenderWare Binary Stream) format is a proprietary binary format used by RenderWare graphics engine, primarily for games such as Grand Theft Auto III , Vice City , San Andreas , and Bully . Converting OBJ to DFF is necessary for modding or integrating custom models into RenderWare-based games.