A Generalized Web3D API for Metaverse Bookmarks

Sharing identical 3D scene states across different platforms and user sessions poses practical limitations. Existing mechanisms such as X3D anchors, glTF camera tags, and proprietary URL-based encodings typically support only static, author-defined viewpoints or are constrained to a specific viewer implementation. This paper introduces a schema and API for a Web3D Bookmarking system that enables interoperable sharing of precise, user-generated 3D scene contexts. The proposed grammar encodes the complete scene state, including camera parameters, navigation settings, scene composition, and contextual metadata, into a compact descriptor suitable for embedding in hyperlinks or other distribution methods. When accessed, the scene is re-instantiated with the same view and context as intended by the original sharer. We define the grammar using a formal JSON Schema and justify each parameter through a design rationale. Use cases include collaborative VR/AR environments, remote design reviews, and educational applications where reproducible scene context is critical. An initial implementation using X3D and X3DOM demonstrates feasibility. We also compare our approach with existing viewpoint sharing techniques and outline a structured evaluation plan to assess the utility and performance of the proposed system.