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Björn Hartmann bjoern@cs.stanford

Understanding & Modeling Input Devices. Björn Hartmann bjoern@cs.stanford.edu. Questions for today. How do common input devices work? How can we think about the larger space of all possible input devices? Can we predict human input performance?

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Björn Hartmann bjoern@cs.stanford

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  1. Understanding & Modeling Input Devices Björn Hartmannbjoern@cs.stanford.edu

  2. Questions for today How do common input devices work? How can we think about the larger space of all possible input devices? Can we predict human input performance? Next class: What about uncommon input devices (music controllers, multitouch, …)?

  3. Today’s lecture in graph form Level of abstraction abstractmodels Functional Dissection of Mouse & Keyboard Design Space of Input Devices Modeling Human Performance concretedetails time

  4. I spilled coffee on my keyboard. Now 25% of the keys don’t work anymore. But some of the defective keys are nowhere near the spill. What’s going on?

  5. Key cap Top conductive layer Separating layer(with hole) Bottom conductive layer

  6. Key cap Top conductive layer Separating layer(with hole) Bottom conductive layer

  7. Row/Column Scanning 9 lines 20 keys C3 C4 C5 C2 C1 Q W E R T R1 R2 A S D F G R3 Z X C V B R4

  8. Mouse. Engelbart and English ~1964 Source: Card, Stu. Lecture on Human Information Interaction. Stanford, 2007.

  9. A Layered Framework From: Hartmann, Follmer, Klemmer: Input Devices are like Onions

  10. Right button Left button Encoder wheel for scrolling

  11. slotted wheel(between emitter & detector) IR emitter IR detector

  12. Sensing: Rotary Encoder High

  13. Sensing: Fwd Rotation Low

  14. Sensing: Backwd Rotation Oops! Low

  15. Solution: Use two out-of-phase detectors High High

  16. Sensing: Rotary Encoder Low High

  17. Sensing: Rotary Encoder Coding: HH-> LH: dx = 1 HH-> HL: dx = -1 High Low

  18. Transformation cxt = max(0, min( sw, cxt-1+dx*cd )) cyt = … cxt: cursor x position in screen coordinates at time tdx: mouse x movement delta in mouse coordinatessw: screen widthcd: control-display ratio

  19. Device Abstraction Click, DoubleClick, MouseUp, MouseDown, MouseMove …

  20. What about optical mice? Source: http://spritesmods.com/?art=mouseeye

  21. bbbbbbbbbb Source: http://spritesmods.com/?art=mouseeye

  22. Trackball, Trackpad

  23. Trackpoint • Indirect, force sensing, velocity control • Nonlinear transfer function Velocity Force (cc) Image by flickr user tsaiid

  24. Joysticks

  25. Card, S. K., Mackinlay, J. D., and Robertson, G. G. 1991.A morphological analysis of the design space of input devices.ACM TOIS9, 2 (Apr. 1991), 99-122. A design space of input devices…

  26. Implicit Assumptions: Desktop-centric computing

  27. Which device is fastest? • For what task? Pointing. • Combination of two factors: • Bandwidth of human muscle group (upper limit) • Bandwidth of device itself

  28. Bandwidth of Human Muscle Groups Source: Card, Stu. Lecture on Human Information Interaction. Stanford, 2007.

  29. Fitts’ Law • Time Tpos to move the hand to target size S which is distance D away is given by: • Tpos = a + blog2(2D/S) • Time to move the hand depends only on the relative precision required Source: Landay, James. “Human Abilities”. CS160 UC Berkeley.

  30. Mouse vs. Headmouse Source: Card, Stu. Lecture on Human Information Interaction. Stanford, 2007.

  31. Headmouse: No chance to win Source: Card, Stu. Lecture on Human Information Interaction. Stanford, 2007.

  32. Fitts’ Law in Windows & Mac OS Windows 95: Missed by a pixelWindows XP: Good to the last drop The Apple menu in Mac OS X v10.4 Tiger. Source: Jensen Harris, An Office User Interface Blog : Giving You Fitts. Microsoft, 2007; Apple

  33. Fitts’ Law in Microsoft Office 2007 Magic Corner: Office Button in the upper-left corner Larger, labeled controls can be clicked more quickly Mini Toolbar: Close to the cursor Source: Jensen Harris, An Office User Interface Blog : Giving You Fitts. Microsoft, 2007.

  34. http://bjoern.org

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