A Hand-Tracked Rotational Interface for Parameter Input in Mixed Reality CAD

Mixed Reality (MR) offers opportunities to enhance early-stage Computer-Aided Design (CAD) by enabling immersive, spatially integrated workflows. However, current MR CAD systems struggle with precision, efficiency, and intuitive interaction, limiting their professional adoption. This study introduces and evaluates a novel, hand-tracked rotary input system that allows designers to manipulate CAD parameters by twisting, pushing, or pulling a virtual knob, enabling direct interaction without controllers or external menus. The rotary knob was compared with a virtual numpad in an A/B test involving 12 CAD-experienced participants. Tasks assessed speed and accuracy under time constraints and were complemented by subjective workload (NASA TLX), intuitive interaction (INTUI), and observational data. Results show that while the numpad achieved faster and more precise input, the rotary knob encouraged sustained focus on the 3D model and demonstrated rapid learning effects. Participants rated it higher on engagement (“magical experience”) and saw potential for iterative design workflows, though reliability concerns and gesture discomfort highlighted areas for refinement. The findings suggest that, with further optimization, spatially layered input techniques like the rotary knob could complement traditional CAD tools, supporting more human-centered and immersive MR design environments.