Overview and Detail
CS 7450 - Information Visualization February 12, 2004
John Stasko
Fundamental Problem
• Scale - Many data sets are too large to visualize on one screen
− May simply be too many cases
− May be too many variables
− May only be able to highlight particular cases or particular variables, but viewer’s focus may change from time to time
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Overview
• Providing an overview of the data set can be extremely valuable
− Helps present overall patterns
− Assists user with navigation and search
− Orients activities
• Generally start with overview
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Details
• Viewers also will want to examine details, individual cases and variables
• How to allow user to find and focus on details of interest?
• Generally provide details on demand
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Providing Both
• Overview + detail displays can be combined via either time or space
− Time - Alternate between overview and details sequentially in same place
− Space - Use different portions of screen to show overview and details
• Each has advantages and problems
Specific Problem
• Develop visualization and interface
techniques to show viewers both overview + detail, and allow flexible alternation between each
• Potential Solutions????
− Discuss….
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Common Solution
• Scroll
− Provide a larger, virtual screen by allowing user to move to different areas
• Still a problem
− Clunky interaction
− Only get to see one piece
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Worthy Objective
• Allow viewer to examine cases and/or variables in detail while still maintaining context of those details in the larger whole
• Concession
− You simply can’t show everything at once
• Be flexible, facilitate a variety of user tasks
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Nature of Solutions
• Not just clever visualizations
• Navigation & interaction just as important
• Information visualization & navigation
Confound
Devices with even smaller screens are becoming more popular!
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An Example
Detail-only view (from Civilization II game)
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An Example
Overview and detail (from Civilization II game) overview detail
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Plaisant et al Article
• Good introduction to overview/detail issue
• Application concern: viewing and editing large images
• Expanding the notion of the one
dimensional scroll bar: zooming, diagonal panning, multiple detailed views
• List of visualization/interaction solutions
IEEE Software ‘95
1. Detail-only
• Single window with horizontal and vertical panning
• Works only when zoom factor is relatively small
• Example: Windows
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2. Single window with zoom and replace
• Global view with selectable zoom area which then becomes entire view
• Variations can let users pan and adjust zoomed area and adjust levels of magnification
• Context switch can be disorienting
• Example: CAD/CAM
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3. Single coordinated pair
• Combined display of the overview and local
magnified view (separate views)
• Some implementations reserve large space for overview; others for detail
• Issue: How big are different views and where do they go?
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4. Tiled multilevel browser
• Combined global, intermediate, and detail views
• Views do not overlap
• Good
implementations closely relate the views, allowing panning in one view to affect others
5. Free zoom and multiple overlap
• Overview presented first; user selects area to zoom and area in which to create detailed view
• Flexible layout, but users must perform manual window management
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6. Bifocal magnified
• “Magnifying glass”
zoomed image floats over overview image
• Neighboring objects are obscured by the zoomed window
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7. Fish-eye view
• Magnified image is distorted so that focus is at high magnification, periphery at low
• All in one view
• Distortion can be disorienting
• More details next class...
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Remain Task-Driven
The goal is to identify the primary type of task the user will be performing and adapt the browser to best fit the needs of that user
Task Taxonomy
• Image generation: overview is important, but most of time is spent at detail level
− Example: CAD/CAM
• Open-ended exploration: overview not always complete; navigation must be fluent and easily mastered
− Example: Interactive Map
• Diagnostic: high detail, fluent panning and complete image coverage
− Example: Circuitry Design
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Task Taxonomy
• Navigation: global view with increased magnification detail areas; panning and zooming less important
− Example: Geographic Information System
• Monitoring: Global view with multiple detailed views for local troubleshooting;
window management is critical
− Example: Network management
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Browser Taxonomy
• Once the user task has been determined, a browser appropriate to that task can be identified
• Plaisant suggests a browser taxonomy to classify and group browsers with similar features
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Browser Taxonomy
• Static Presentation Browsers
− Single View
Detail-only Zoom-and-replace Fish-eye
Superimposition
− Multiple View
Window-placement strategy Ratio of sizes
Coordination (none / unidirectional / bidirectional) Global view
Browser Taxonomy
• Dynamic Presentation Browsers
− Quality of the Update
− Nature of the Update (“Level of Detail”)
− Zooming Factor
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Additions/Variations
• Since the writing of the article, new techniques and many variations have been developed...
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Magnifier Problem Fix
DragMag Image Magnifier
Ware and Lewis CHI ‘95
Video
hello More text
hello
Bifocal magnified display without problem of obscuring the neighboring items
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Transparent Overlays
Lieberman UIST ‘94
Make detailed view semi-transparent, then overlay overview with it
May even control transparency of each
Important Issue
• The “overview” display may need to present huge number of data elements
• What if there simply isn’t enough room?
− The number of data elements is larger than the number of pixels
• Approaches?
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Two Main Approaches
• 1. Interactive display (add scrolling)
− Is it still an overview?
• 2. Reduce the data
− Eliminate data elements But then is it still an overview?
− Aggregate data elements
• 3. Reduce the visual representation
− Smart ways to draw large numbers of data elements
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Drawing the Overview
Information Mural
Jerding and Stasko InfoVis ‘95, IEEE ToVCG ’98
www.cc.gatech.edu/gvu/softviz/infoviz/information_mural.html
What do you do when your data set is too large for your overview window?
--- More data points than pixels --- Don’t want to fall back on scrolling
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Information Mural
Use techniques of computer graphics (shading and antialiasing) to more carefully draw overview displays of large data sets
Think of each data point as ink and each screen pixel as a bin
Data points (ink) don’t fit cleanly into one bin, some ink may go into neighboring bins
Can map density to gray or color scale
Mural Algorithm
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Mural Example
Object-oriented code executions
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Mural Example
Sunspot activity over 150 years
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Mural Example
Parallel Coordinates
normal
muralized
colorized
Mural Example
Message passing in parallel program
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Mural Example
U.S. Census Data
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Mural Example
Video LaTeX
source file
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Multiple Windows/Views
• Fundamentally, (good) overview & detail involves multiple views
• When should you use multiple views?
• What makes a good multiple view system?
Design Guidance
• Nice paper with many design guidelines
• Model of multiple view system
− 1. Selection of views
− 2. Presentation of views
− 3. Interaction among views
Wang Baldonado, Woodruff, and Kuchinsky
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When to Use Mult. Views
• Diversity - Use m.v. when there is a diversity of attributes, models, user profiles, levels of abstraction or genres
• Complementarity - Use m.v. when different views bring out correlations and/or disparities
• Decomposition - Partition complex data into m.v. to create manageable chunks and to provide insight into the interaction among different dimensions
• Parsimony - Use m.v. minimally
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How to Use Multiple Views
• Space/Time Resource Optimization- Balance the spatial and temporal costs of presenting m.v. with the spatial and temporal benefits of using the views
• Self Evidence - Use perceptual cues to make relationships among m.v. more apparent to the user
• Consistency - Make interfaces for m.v. consistent, and make the states of m.v. consistent
• Attention Management - Use perceptual cues to focus the user’s attention on the right view at the right time
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Still to come...
• Related topics coming up:
− Focus + Context views
Typically one display window or view for both overview and detail that uses some form of distortion to combine them
− Panning and zooming
More detailed study of interaction techniques to support overview and detail displays
HW4
• Work with two hierarchy visualizers:
SequoiaView and Grokker
• Understand and critique visualizations and user interfaces
• Shorter evaluation: <5 pages
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Upcoming
• Focus & context
− Reading Chapter 7 Sarkar & Brown
• Panning and zooming
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References
• Spence and CMS books
• All referred to articles
• S. Meier, Civilization II. MicroProse:1998 http://www.civ2.com
• Demonstration maps generated at MapQuest, http://www.mapquest.com
• F’99 slides from Voida, Zhang, Zook and Stenger
