This paper proposes a group mapping mechanism for a 3D blog system that enables system to more systematically and effectively support collaboration on the Internet. The 3D blog system enables users to interact with a 3D model, annotate any spot on the model, and publish the annotations in a blog entry along with viewpoint information, making it easier for the user to communicate with other people and share interests, ideas, and questions about 3D models. The 3D blog system uses the viewpoint information to detect similar entries and automatically creates TrackBack links to enable users to easily find people who may have similar interests. However, there is no way to group similar interests in the 3D blog system. Therefore, we propose a group mapping mechanism that dynamically categorizes the similar entries in different users' blogs. This collaborative 3D blog system is expected to promote the emergence of communities of people who share interests and to support communication in those communities.