3D environments represent a great opportunity for universal access to information, as they offer an intuitive interaction paradigm, similar to what is experienced by humans in their everyday lives. In spite of that, several 3D interfaces are characterized by poor structures and are hard to navigate. This paper presents the multimodal concept of the Interaction Locus (IL) as a means to give structure to 3D scenes, helping the user to interact with and access information inside them. The concept was initially developed with particular reference to desktop virtual reality (2.5 D virtual reality), but it is general enough to be extended to other contexts, such as real 3D scenes. The final part of this work shows how the IL concept addresses the need for a unified authoring methodology, capable of allowing access to different target user groups from a variety of different devices.