MagicPen: Enabling Dynamic Physical Scaffolding through Haptic Feedback for 3D Content Creation in VR with a Variable-length Stylus

Stylus interaction is widely used for 3D content creation. In VR, it is typically mid-air, offering spatial freedom while lacking the grounded haptic feedback required for both shape perception and active geometric editing. To address this, we present MagicPen, a variable-length stylus that delivers grounded haptic feedback and enables active 3D editing through on-surface interaction. MagicPen operates through dynamic physical scaffolding, an interaction approach that adjusts the length to the interaction context: compliantly rendering geometry the user is actively creating, or resistively rendering predefined virtual geometry as a rigid constraint. We conducted three user studies comparing MagicPen with mid-air interaction in terms of accuracy, task load, and user preference: (1) single-axis positioning for depth precision; (2) freeform 3D planar drawing in compliant mode; and (3) drawing on rendered geometry in rigid mode. Results show MagicPen improves depth positioning. MagicPen better supports 3D content creation by enabling grounded shape perception.