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Shift: A Technique for Operating Pen-Based Interfaces Using Touch. Daniel Vogel University of Toronto. Patrick Baudisch Microsoft Research. Motivation. Motivation. Motivation. Small Targets. Small Targets. Advantages of the Pen. Pen. Finger. unique contact point.
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Shift: A Technique for Operating Pen-Based Interfaces Using Touch Daniel Vogel University of Toronto Patrick Baudisch Microsoft Research
Advantages of the Pen Pen Finger unique contact point ambiguous contact point finger occludes target remove hand from screen
Offset Cursor (Potter et al. 1988) Pen Offset Cursor
Offset Cursor (Potter et al. 1988) • Disadvantages • no visual feedback until contact, need to estimate offset • makes some display areas inaccessible • unexpected offset affects walk-up-and-use scenarios
Benefit 1: Aim for the Target • Users expect to click on the target itself. • allows switching between pen and touch • walk-up and use with kiosk
Benefit 1: Aim for the Target • Users expect to click on the target itself. • allows switching between pen and touch • walk-up and use with kiosk
Benefit 2: All Areas Accessible • Callout is relative to finger, so it can go anywhere. • no edge problems
Benefit 2: All Areas Accessible • Callout is relative to finger, so it can go anywhere. • no edge problems
Benefit 3: Fast For Large Targets • Callout only used when necessary • same speed as unaided touch screen for large targets
Model Performance Model
Escalation • Based on selection ambiguity with fallback to hesitation. • ST = Target Size, SF = Finger occlusion threshold • ST << SF high selection ambiguity no delay • ST >> SF no selection ambiguity long delay • ST≈SF “ambiguous selection ambiguity” short delay
Escalation • Based on selection ambiguity with fallback to hesitation. • ST = Target Size, SF = Finger occlusion threshold • ST << SF high selection ambiguity no delay • ST >> SF no selection ambiguity long delay • ST≈SF “ambiguous selection ambiguity” short delay
Perceived Input Point Correction • Users expect selection point to be higher. user’s view hardware’s view • Iterative estimate for a correction vector V using difference between initial contact point P1 and final lift off point P2 • Vt+1 = Vt + w(P2 - P1)
Experimental Design • 3 techniques (Shift, Touch, Offset Cursor) x • 2 finger styles (nail, tip) x • 3 blocks x • 6 target sizes (6, 12, 18, 24, 48, 96px) x • 4 target directions (NW, NE, SW, SE)
Discussion • Able to select small targets reliably (like Offset Cursor) • Fast for large targets (like unaided Touch Screen) • However, biggest benefit may be simpler mental model: • “Just aim for the target”
High Accuracy Enhancements • Added Zooming and CD-Ratio Manipulation
High Accuracy Enhancements • Added Zooming and CD-Ratio Manipulation
Thanks to members of the ASI and VIBE groups at MSR, special thanks to Raman Sarin, Ed Cutrell, and David Thiel.
Estimating Occlusion Threshold • Don’t know actual finger size, so estimate it over time • when ST≈SF short delay … means user can choose to use escalation by hesitating or not • if they hesitate and use escalation make SF larger • if they just click without escalation make SF smaller