ScratchVR: Low-Cost, Calibration-Free Sensing for Tactile Input on Mobile Virtual Reality Enclosures

We extend the interaction space of low-cost mobile virtual reality (VR) by introducing bidirectional scrolling and discrete selection using magnetic sensing. Our design uses the original Google Cardboard v1 input components, modifying only the cardboard mounted on the side. Users slide the magnetized washer around a circular track on the outer layer, which drags a magnet on the inner layer across asymmetric patterned ridges. The phone's magnetometer detects the position of the magnet as it moves around the track and slots into each ridge, emulating a click wheel. The phone's accelerometer is used to recognize center button taps. We compare our system against the current best practice (gaze) with 12 participants across four VR navigation and selection tasks. Finally, we demonstrate our system robustly handles continuous input, despite some minor deterioration of the cardboard, using a motorized rig over an 8-hour period.