Angle and pressure-based volumetric picking on touchscreen devices

The target picking in 3D volumetric data is a common interaction problem in a variety of domains such as medicine, engineering, and physics. When a user clicks on a 2D point on the screen rendering, the ray is cast through the volume at an angle perpendicular to the screen. The problem lies in determining the intended location of picking, that is the end point of the ray. We introduce picking for 3D volumetric data by utilizing pressure and angle of the digital stylus pen on a touchscreen device. We map both pressure and angle of the stylus to the depth of the selector widget to help target acquisition. We evaluate several methods of selection: single finger selection, stylus with pressure but without an angle, and stylus with both angle and pressure. We decouple rotation of the volumetric data, and control for two target sizes. We report significant benefits of digital stylus picking methods and a relation between the methods and target sizes.