The progress and the continuous evolution of computer capacities, as well as the emergence of the X3D standard have recently boosted the 3D domain. Still, 3D data management remains expensive. Lot of (human and materiel) resources are needed to properly create 3D objects. In order to speed up the construction of new 3D objects, the reuse of existing objects is to be considered. Associating some semantics with 3D contents becomes a major issue specially for reusing such contents or pieces of content after having extracted them from existing 3D scenes. In this paper, we address this issue by proposing a generic semantic annotation model for 3D, called 3DSEAM (3D Semantics Annotation Model). 3DSEAM aims at indexing 3D contents considering visual, geometric, topologic and semantic aspects. We extend MPEG-7 in order to support the localisation of 3D objects. With this extension MPEG-7 can be used in order to instantiate the 3DSEAM model. Thus; through specific 3D locators 3DSEAM can attach some visual, geometric and semantic features with 3D objects defined within X3D fragments. These features can be indexed and then combined in order to formulate complex queries.