Geometrically Consistent Projection-Based Tabletop Sharing for Remote Collaboration

Projection-based tabletop sharing (PBTS) systems allow a local user to share a pointing gesture or a handwritten note on a tabletop document with a remote user who places the same document on a tabletop by projecting the upper limb image of the local user onto the remote document and tabletop. A vertical display is used to share an image of the upper body, including the face of the remote user. However, in previous systems, the spatial layouts of the shared documents must be identical on both tabletops, and the projected upper limb is not extended from the upper body image of the remote user. This paper proposes a PBTS system to address such geometric consistency issues to improve remote collaboration. First, we propose to maintain the geometric consistency of a pointing gesture and handwritten note between each pair of the shared documents rather than between the entire tabletops. This allows users to freely change the document layouts on both tabletops. Second, we propose to overlay the upper limb image such that it is extended from the vertical display, where the upper body image is shown. This is achieved by rotating the upper limb image around the fingertip that performs the pointing gestures or around the tip of the pen used to write notes. We constructed a prototype to determine if the proposed system resolves the geometric consistency issues. Then, we evaluated how accurately a user can convey a pointing position to a distant partner when the document layouts differ between the remote tabletops. Finally, we evaluated how the user experience, particularly the social presence, is improved by the proposed geometrically consistent upper limb direction.