The progress and the continuous evolution of computer capacities, as well as the emergence of the X3D standard have recently boosted the 3D domain. 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 and semantic aspects. 3DSEAM is instantiated using MPEG-7 that we have extended with 3D specific locators. These locators link some visual, geometric and semantic features to the corresponding X3D fragments. These features can then be used for indexing and querying.