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Tovi Grossman, Ravin Balakrishnan
Dep. of Computer Science Univ. of Toronto
CHI 2004
Introduction
Background
Goals and Directions of the Current Study
Experiment
Implications for User Interface Design
Conclusion
Advances in three dimensional display technology
Appropriate user interfaces
: easily select and manipulate virtual elements in the 3D display space.
They studied and modeled user performance in the most fundamental
interaction task – pointing – in a 3D display.
Contents of paper
review previous work on pointing and Fitts’ law models in 1D and 2D
identify various factors and interactions between them in 3D pointing
propose several mathematical models
controlled experiment
Implications for user interface design
Fitts’ law One dimension
Two dimension (Mackenzie and Buxton, 1992)
Accot and Zhai (2003) : A weighted Euclidean model
Ware et al. (1994, 1997) : 3D model, similar to 2D model
A
W
A
W
H
Experimental Hardware Platform : volumetric display was used Manipulation of Experimental Parameters
Target dimension : W, H, D Movement angle : Ө uses a approach angle of 0°
Modeling First baseline model & Weighted model
Weighted Euclidian model
Incorporating f( ) into the IDӨ Wtmin model
Incorporating f( ) into the IDӨ WtEuc model
Apparatus
Participants 5 female and 7 male, ages from 20 to 25
Procedure : cuboids target, XZ plane, 3D cursor Design
A(3)ⅩH(4)ⅩW(4)ⅩD(4)Ⅹangle(3) = 576 combinations, 3 sessions, random order 6 reciprocal movements, 2 practices, 6 groups, 1 hour per each session
Performance measure Movement time, number of errors per trial
Movement time analysis Main effect : all had a main effect on MT (angle : 0, 45, 90) Effect of movement direction : no effect Interactions ( Ө↔ W, D, H) : no HⅩθ → targets were located in the XZ plane Relative effect of target dimensions : Figure 4e Interactions betw. target dimensions : Figure 5
Movement time analysis Main effect : all had a main effect on MT (angle : 0, 45, 90) Effect of movement direction : no effect Interactions ( , W, D, H) : Ө no HⅩθ Relative effect of target dimensions Interactions betw. target dimensions
Movement time analysis Fit of the models
Error analysis : effects for D,H,W, no effect for A, error rate 15.7%, 0.04 units → error ↑
“racing through the experiment”
Target sizing
target size → error rate
dimension parallel to the line of approach
Target positioning
moving forward and backward → left and right
adjust the layout of the interface elements according to the position of users
A true 3D volumetric display
Moving forwards and backwards in depth is
slower than moving left and right for selecting targets.
The target width was more critical than the height and depth of the target.
The effect of the height was constant regardless of the movement angle.
Accounts for varying movement angles
The implications of our results for the sizing and positioning of user
interface widgets in 3D displays
Accot, J., & Zhai, S. , Refining Fitts' law models for bivariate pointing. ACM
CHI. p. 193-200., 2003
MacKenzie, S. , Fitts' law as a research and design tool in human-computer
interaction, Human-Computer Interaction. 7. p. 91-139., 1992
MacKenzie, S., & Buxton, W., Extending Fitts’ law to two-dimensional
tasks, ACM CHI. p. 219-226., 1992
※ Murata, A., Iwase, H., Extending Fitts’ law to a three-dimensional pointing
task, Human Movement Science Vol 20, pp.791-805., 2001