What We Are Going to Learn

• No unjustified 3D or 2D
• Readable text
• Eyes beat memory
• Visualization mantra
• Responsiveness is required
• Function first, form next

No Unjustified 3D

Unjustified 3D Everywhere

Power of the Plane

Power of the Plane (cont.)

Danger of Depth

• Acquire more info on image plane quickly from eye movements
• Acquire more info for depth more slowly, from head/body motion

Occlusion Hides Information

• Interaction can resolve occlusion...
• ... but at cost of time and cognitive load

Perspective?

• Interferes with all size channel encodings
• Power of the plane is lost!

3D vs. 2D Bar Charts

• 🚫 3D bars🚫
• Perspective distortion
• Occlusion
• 2D faceting 👌🏻

Tilted Text Isn’t Legible

• Tilted text 👉 poor legibility


• Further reading:
  [Exploring and Reducing the Effects of Orientation on Text Readability in Volumetric Displays.
Grossman et al. CHI 2007]

Transform to New Data Abstraction

• Derived data: cluster hierarchy
• Juxtapose multiple views (calendar)
• Superimposed 2D curves (clusters)

When to Use 3D

Shape perception

• Benefits outweigh costs when target is shape

When to Use 3D

• Use 3D for true 3D spatial data. 👍
• 3D needs very careful justification for abstract data.
  • Enthusiasm in 1990s, but now skepticism
  • Be especially careful with 3D for point clouds or networks

No Unjustified 2D

Do You Really Need a Map?

• They use the position location
• Use them for geographical tasks
• Bad for comparison tasks
• Don't use a map just because you have geo data

Eyes Beat Memory

Eyes Beat Memory

• Principle: external cognition vs. internal memory
• Easy to compare by moving eyes between side-by-side views
• Harder to compare visible item to memory of what you saw

Eyes Beat Memory (cont.)

• Implications for animation
• Great for choreographed storytelling
• Great for transitions between two states
• Poor for many states with changes everywhere
• Consider small multiples instead

Example: Cerebral

• Small multiples: one graph instance per experimental condition
• Same spatial layout
• Color differently, by condition

Why Not Animation?

• Disparate frames and regions: comparison difficult
• Vs. contiguous frames
• Vs. small region
• Vs. coherent motion of group
• Safe special case
• Animated transitions

Change Blindness

Resolution Beats Immersion

• Immersion typically not helpful for abstract data
• Do not need sense of presence or stereoscopic 3D
• Desktop also better for workflow integration
• Resolution much more important: pixels are the scarcest resource
• Virtual reality for abstract data difficult to justify thus far
• But stay tuned with second wave

Visualization Mantra

Visualization Mantra

• Overview first, zoom and filter, then details on demand
• Overview first, zoom and filter, then details on demand
• Overview first, zoom and filter, then details on demand
• Overview first, zoom and filter, then details on demand
• Overview first, zoom and filter, then details on demand
• Overview first, zoom and filter, then details on demand
• Overview first, zoom and filter, then details on demand
• Overview first, zoom and filter, then details on demand
• Overview first, zoom and filter, then details on demand
• Overview first, zoom and filter, then details on demand

Overview

• Overview 👉 summary
• Microcosm of full visualization design problems
• Useful for exploration

Bottom-Up?

Function First,
Form Next

Function First

• Start with focus on functionality
• Possible to improve aesthetics later on, as refinement
• If no expertise, seek for help from graphic designers
• Dangerous to start with aesthetics
• Usually impossible to add function retroactively

Aesthetics Do Matter

• Another level of function
• Visual hierarchy, alignment, flow
• Gestalt principles in action
• Very important for the enjoy task

Responsiveness Is Required

• 0.1 seconds: perceptual processing
• Subsecond response for mouseover highlighting: ballistic motion
• 1 second: immediate response
• Fast response after mouseclick, button press: Fitts’s Law limits on motor control
• 10 seconds: brief tasks
• Bounded response after dialog box: mental model of heavyweight operation (file load)

Scalability Considerations

• Highlight selection without complete redraw of view (graphics frontbuffer)
• Show ⏳ for multi-second operations (check for cancel/undo)
• Show progress bar for long operations (process in background thread)
• Rendering speed when item count is large (guaranteed frame rate)

Basic Design Principles

Basic Design Principles

• Proximity
• Alignment
• Repetition
• Contrast

Proximity

• Do group related items together
• Avoid equal whitespace between unrelated

Alignment

• Do find/make strong line, stick to it
• Avoid automatic centering

Repetition

• Do unify by pushing existing consistencies

Contrast

• If not identical, then very different
• Avoid similar

Labels and Axis

Labeling

• Make visualizations as self-documenting as possible
• Meaningful and useful title, labels, legends

Labeling (cont.)

• Axes and panes/subwindows should have labels
• And axes should have good mix/max boundary tick marks
• Everything that’s plotted should have a legend
• And own header/labels if not redundant with main title
• Use reasonable numerical format
• Avoid scientific notation in most cases

Avoid Dual Axis

• Apples vs. oranges
• Which one is which?

Be Careful with Aggregations

• Mean vs. median
• Show standard deviations
• Show uncertainty
• Does the aggregation make sense?
• Cars and motorcycles have, on average, three wheels
• Summing up grades (instead of averaging)

Normalize

• When comparing, using a common metric
• Usually percent
• Always state percent to what

Ethics

Thought exercise

What We Learned

• No unjustified 3D or 2D
• Readable text
• Eyes beat memory
• Visualization mantra
• Responsiveness is required
• Function first, form next