We present a 3D container model that enables the compositing of 3D file formats. It allows not only to compose 3D scenes made of several 3D files of different types but also to combine their functionalities and to make them interact together in the rendering window. This model, calls 3DFC for 3D File Container, relies on the Scene Graph Adapter (SGA) architecture that makes it possible to load any scene-graph-based 3D file format in a 3D application whatever the involved engines (rendering engine, physics engine, etc.). This paper describes the 3DFC model, its integration with the SGA architecture and gives an implementation example. In this example we define a scene composed of an X3D file and a Collada file and we make their content interact in a 3D application that relies on Ogre 3D and Bullet.