Tech-note: Dynamic Dragging for Input of 3D Trajectories

We present Dynamic Dragging, a virtual reality (VR) technique for input of smooth 3D trajectories with varying curvature. Users "drag" a virtual pen behind a hand-held tracked stylus to sweep out curving 3D paths in the air. Previous explorations of dragging-style input have established its utility for producing controlled, smooth inputs relative to freehand alternatives. However, a limitation of previous techniques is the reliance on a fixed-length drag line, biasing input toward trajectories of a particular curvature range. Dynamic Dragging explores the design space of techniques utilizing an adaptive drag line that adjusts length dynamically based on the local properties of the input, such as curvature and drawing speed. Finding the right mapping from these local properties to drag line length proves to be critical and challenging. Three potential mappings have been explored, and results of informal evaluations are reported. Initial findings indicate that Dynamic Dragging makes input of many styles of 3D curves easier than traditional drag-style input, allowing drag techniques to approach the flexibility for varied input of more sophisticated and much harder to learn techniques, such as two-handed tape drawing.