Recently, the use of digital styluses is challenged by air painting applications such as Painter Freestyle [Sutton 2013], Ethereal for Photoshop (http://drivenpixels.com/ethereal), and Fantasia Painter (https://apps.leapmotion.com/apps/fantasia-painter/windows). By utilizing the hand tracking capability of Leap Motion controller, these applications show that painting in the air using hands movement is much more flexible in artistic improvisation due to high degrees of freedom (DoFs) to control virtual brushes. Nevertheless, air painting is still premature to eliminate styluses because it lacks of some important features of modern digitizers, including 1) the tight overlap of operating and displaying planes to achieve WYSIWYG, 2) the natural analogy of physical painting brush to lower the learning curve, and 3) the possibility of complex haptic feedbacks from the canvas for intuitive fine control of brush strokes. Moreover, without holding a stylus and touching the canvas, its difficult to control brush movement accurately and steadily, which may lead to unexpected stroke jittering.