Input Devices and Interaction Techniques

I. Scott MacKenzie

Summarized and Augmented by Geb Thomas

Introduction

• Input and output between people and machines

• New technology, new challenges

• Interaction experiments and models

Transducers

• Convert energy -- often mechanical to electrical

• Switches (mechanical and photoelectric)• Isotonic (displacement) joysticks - position

encoders• Isometric (force sensing) joysticks - strain

guages• Microphones

A Mouse

Joysticks

http://www.vrealities.com/control.html

http://www.thevrsource.com/

GlovesCyberglove

http://www.virtex.com/products/hw_products

Pinch glove

TrackersPolhemus (Fast Track)

Flock of Birds (Virtex)

Intersence (IS300)

Device Models

• Buxton’s taxonomy -- articulation, number of dimensions, type of sensing (position, motion, pressure), motor skills (touch vrs mechanical)

• Foley tasks -- select, position, orient, path, quantify and text entry -- emphasizes mappings

• Very few engineering models

Device Parameters

• Resolution

• Sampling Rate

• Lag

• Optimality and control gain

• Some of these are determined by hardware, some by software, some by transducer characteristics

Resolution

• Nonlinearity, monotonicity, offest and gain

Sampling Rate

• Often 10-100 Hz

• Too slow for gesture capture

• Nyquest frequency

Lag

• Time difference between controller input and display

• 3D trackers range 30 - 250 mx, depends on sampling rate, update rate and software overhead.

Optimality and Control Gain

• Tunable parameters, such as mouse gain

• Selection task optimization does not consider “human engineering factors” such as – Ease of learning– skill retention– fatigue– effort– strees

Mouse Gain

Nonlinear Gain

Vd = k*Vc^2

Interaction

• Movement is of increasing importance

• Many researchers considering mapping of 2D -> 3D

• Must be trained

• Limited metaphors

• Perceptual structure requires good match between input space and output space– Twisting for dials, shoving for movement, 2D for 2D,

3D for 3D

Gestures

• The great new era :)

• Writing, scribbling, annotating, pointing, nodding, etc.

• Editing proofreaders marks

• Transcribing musical notation

• Brush strokes

Tactile and Force Feedback

• Good input requires good feedback

• shape encoding in manual controls

• Character drawing the Octagon, a 24x6 matrix of pins

• Minski’s sandpaper

• Akamatsu and Sato’s variable friction

• Zimmerman’s pinch glove