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Precise Selection Techniques for Multi-Touch Screens

This study explores precise selection techniques for multi-touch screens, addressing challenges such as small target size, finger occlusion, shaking, and lack of hover state. The study compares different dual finger selection techniques and evaluates their effectiveness and user preferences.

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Precise Selection Techniques for Multi-Touch Screens

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  1. Precise Selection Techniques for Multi-Touch Screens Hrvoje Benko Andy D. Wilson Patrick Baudisch Columbia University and Microsoft Research CHI 2006

  2. Selecting a small target is very HARD! CHI 2006

  3. Small target size comparison • Average finger ~ 15 mm wide CHI 2006

  4. Touchscreen Issues • Finger >>> Target • Finger occludes the target • Fingers/hands shake and jitter • Tracking can be noisy (e.g. video) • No hover state (hover == drag) CHI 2006

  5. Solutions based on single touch interfaces and complex on-screen widgets: Albinsson, P. A. and Zhai, S. “High Precision Touch Screen Interaction.” (CHI ’03) Previous Work Sears, A. and Shneiderman, B. “High Precision Touchscreens: Design Strategies and Comparisons with a Mouse.” (’91) CHI 2006

  6. Dual Finger Selections • Multi-touch techniques • Single fluid interaction • no lifting/repositioning of fingers • Design guidelines: • Keep simple things simple. • Provide an offset to the cursor when so desired. • Enable user controlled control-display ratio. CHI 2006

  7. Simulating Hover State • Extension of the “area==pressure” idea (MacKenzie and Oniszczak, CHI 1998) • Problem: • LARGE area difference  reliable clicking • SMALL movement (i.e. SMALL area difference)  precise and accurate clicking CHI 2006

  8. Clicking gesture – “finger rocking” Goal: Maximize ∆ touch area Minimize ∆ cursor location SimPress (Simulated Pressure) CHI 2006

  9. Top Middle Cursor Large ∆ touch area Small ∆ cursor loc. Center-of-Mass Cursor Large ∆ touch area Large ∆ cursor loc. SimPress Cursor Placement CHI 2006

  10. SimPress in Action CHI 2006

  11. Dual Finger Selections • Offset • Midpoint • Stretch • X-Menu • Slider Primary finger  cursor position & click Secondary finger  cursor speed or C/D CHI 2006

  12. Dual Finger Offset • Fixed offset WRT finger • Ambidextrous control CHI 2006

  13. Dual Finger Midpoint • Cursor  ½ distance between fingers • Variable speed control • Max speed reduction is 2x • Dead spots on screen! CHI 2006

  14. Dual Finger Stretch • Inspired by ZoomPointing (Albinsson & Zhai,‘03) • Primary finger anchor • Secondary finger • defines the zooming area • scales the area in all directions away from the anchor CHI 2006

  15. Dual Finger Stretch • Offset is preserved after selection! CHI 2006

  16. Bounding Box Zoom Fingers placed OFF target Target distance increases w/ zoom “Stretch” Zoom Primary finger placed ON target Same motion = 2x zoom Zooming Comparison CHI 2006

  17. Crossing Menu (no buttons/no clicks) 4 speed modes 2 helper modes Cursor notification widget Eyes-free interaction Freezing cursor Quick offset setup Eliminate errors in noisy conditions Helpers: Snap – Remove offset Magnification Lens Dual Finger X-Menu CHI 2006

  18. Dual Finger X-Menu CHI 2006

  19. Dual Finger X-Menu with Magnification Lens CHI 2006

  20. Dual Finger Slider Freeze Slow 10X Slow 4X Normal Snap CHI 2006

  21. Dual Finger Slider CHI 2006

  22. Multi-Touch Table Prototype • Back projected diffuse screen • IR vision-based tracking • Similar to TouchLight (Wilson, ICMI’04) CHI 2006

  23. User Experiments • Measure the impact of a particular technique on the reduction of error rate while clicking • 2 parts: • Evaluation of SimPress clicking • Comparison of Four Dual Finger Techniques • Task: • Reciprocal target selection • Varying the square target width • Fixed distance (100 pixels) • 12 paid participants (9 male,3 female, ages 20–40), frequent computer users, various levels of touchscreen use CHI 2006

  24. Within subjects repeated measures design 5 target widths: 1,2,4,8,16 pxls Hypothesis: only 16 pxls targets are reliably selectable Results: 8 pixel targets still have ~10% error rate Part 1: SimPress Evaluation F(4,44)=62.598, p<0.001 CHI 2006

  25. Part 2: Comparison of 4 Dual Finger Selection Techniques • Compare: Offset, Stretch, X-Menu, Slider • Varying noise conditions • Inserted Gaussian noise: σ=0, 0.5,2 • Within subjects repeated measures design: • 3 noise levels x 4 techniques x 4 target widths (1,2,4,8 pxls) • 6 repetitions  288 trials per user • Hypotheses: • Techniques that control the C/D will reduce the impact of noise • Slider should outperform X-Menu CHI 2006

  26. Part 2: Error Rate Analysis • Interaction of Noise x Technique F(6,66)= 8.025, p<0.001 CHI 2006

  27. Part 2: Error Rate Analysis • Interaction of Width x Technique F(9,99)=29.473, p<0.001 CHI 2006

  28. Analysis on median times Stretch is ~ 1s faster than Slider/X-Menu (t(11)=5.011, p<0.001) Slider similar performance to X-Menu Missing Part 2: Movement Time Analysis CHI 2006

  29. Subjective Evaluation • Post-experiment questionnaire (5 pt Likert scale) • Most mental effort: X-Menu (~2.88) • Hardest to learn: X-Menu ( ~2.09) • Most enjoyable: Stretch (~4.12), Slider (~4.08) • No significant differences WRT fatigue CHI 2006

  30. Conclusions and Future Work • Top performer & most preferred: Stretch • Slider/X-Menu • Comparable error rates to Stretch • No distortion of user interface • Cost: ~1s extra • Freezing the cursor (positive feedback) • Like “are you sure?” dialog for clicking… • Possible future SimPress extensions: • Detect user position/orientation • Stabilization of the cursor CHI 2006

  31. Questions

  32. Multi-Touch Tabletops • MERL DiamondTouch (Dietz & Lehigh, ’01) • SmartSkin (Rekimoto, ’02) • PlayAnywhere and TouchLight (Wilson, ’04, ’05) CHI 2006

  33. ANOVA Table CHI 2006

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