ForceExtension: Extending isotonic position-controlled multi-touch gestures with rate-controlled force sensing for 3D manipulation

Recent advances in multi-touch technology have enabled pressure sensing of each touch point on a multi-touch touchpad in addition to position tracking. In this paper we propose two novel approaches for utilizing this extra dimension of input to extend the effect range of position controlled multi-touch gestures. Both ForceExtension approaches are only activated when the averaged force of all active fingers reaches a threshold. The first approach, context-force extension, tracks the most recent position-control movement as the context and combines it with the force input as an isometric rate-controlled extension. The second approach, shear-force extension, scales the micro displacement of the active fingers with the force input to simulate shear-force sensing as a viscoelastic rate-controlled extension. We collected feedback from several users who were asked to perform a 3D search task using variations of these interfaces. A single force sensing multi-touch touchpad was used to control the first-person camera during the search, and the multi-touch gestures to pan, rotate, and zoom the 3D camera were augmented through ForceExtension. Users preferred a medium gain position control combined with the context-force extension.