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Display Techniques in Information-Rich Virtual Environments
Experimental Summary
August 2005
Nicholas F. Polys
Contents
1. Overview
2. Experiment 1
3. Experiment 2
4. Conclusions from Tested Techniques
5. Selected Publications
Overview
The design challenges and techniques of integrated information spaces boil down to the problem
of combining of virtual environment (a.k.a. structure-centric visualization) and information
visualization (a.k.a. attribute-centric visualization) representations. A virtual environment can be
described as a 'Structure-centric' visualization where spatial/perceptual information is depicted.
'Attribute-centric' visualizations are any depiction of abstract information. We have recently
formalized this research area of interface design under the moniker “Information-Rich Virtual
Environments (IRVEs) [3].
Specifically, the goal of this research program is to understand the tradeoffs of various IRVE
information design patterns in their support for fundamental IRVE tasks such as Search,
Comparison, and Finding Patterns and Trends [7, 8]. While supporting information architectures
and runtime systems are required, the crucial issue remains one of design: how can IRVE
interfaces present and manage the volume and diversity of information in a comprehensible
way? How can applications support users in relating abstract and spatial information, and how
they can use those relations to understand patterns or trends within and between the respective
data types?
We have summarized the motivating Research Question as follows [12]:
Where and How should (enhancing) abstract information be displayed
relative to its perceptual referent so that
the respective information can be understood together and separately?
Given an information-rich data set and a set of user tasks, we hope to provide guidelines
determine appropriate mappings of data to interactive display. The (revised) IRVE design space
is shown in Table 1.
Visual Attributes
Representation
Association
Layout Space
Aggregation
Size
Text
Connectedness
Identity
Flat
Color
Scatterplot
Common Region
Object
Hierarchical
Brightness
Line Graph
Proximity
World
Directed
Transparency
Bar Graph
Similarity
User
Network
Font Size
Pie Chart
Common Fate
Viewport
…
Font Type
…
Display
Table 1: Revised Information Design Dimensions for IRVEs with our experimental focus highlighted
Research to date has been focused on the occlusion/association tradeoff for the display of
annotations in IRVEs. From a perceptual standpoint, the visual coupling of annotations to their
referent relies on both Gestalt and Depth cues in the visual buffer. What are advantageous
visual configurations that reduce cognitive overhead by facilitating the conceptual binding of
annotation and referent?
There is a growing literature on multimedia illustration and learning processes. In this work on
IRVEs however, we are concerned with the principal visual design tradeoff that exists between
the (Gestalt) Association and the Layout Space dimensions. This tradeoff occurs because the
stronger the cues of association (visual coupling), the more of the spatial environment is
occluded; the less visual coupling, the less occlusion.
The design matrix of cues is shown in Table 2. Depending on the technique used, Layout
Spaces may portray different depth cues; however, the organizing principle of Layout Space is
based on the coordinate system annotations is be resident in. Figures 1 and 2 illustrate the
nature of each cue.
Connectedness
Object
World
User
Viewport
Display
Common Fate
Similarity
Proximity
Common
Region
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Table 2: the orthogonal Layout Space and Association dimensions in IRVE design
In order to understand the strengths and contributions of these different cues for relating abstract
and spatial information in Search and Comparison tasks, we have run 2 experiments which are
summarized in sections 2-4. The software framework supporting these IRVE interfaces was
developed in conjunction with the PathSim project [6, 4, 7, 10].
Figure 1: IRVE Layout Spaces, a schematic view
Figure 2: Gestalt principles in the Association dimension (image plane). Common Fate is a Gestalt
Association cues that requires interactivity (e.g. selection) or animation.
Experiment 1 (Polys et al [12])
In this experiment, we examined the performance of an Object Space layout and a
Viewport Space layout (Figure 3) for Search and Comparison tasks. We set out with the
following questions:



“Is one layout space with guaranteed visibility better than one with guaranteed tight
spatial coupling for certain tasks?”.
“Do the advantages of visibility or tight spatial coupling hold if the screen size is
increased?”
“Do the advantages of visibility or tight spatial coupling hold if the SFOV is
increased?”
We controlled for size and reabability between conditions, but the Object Space provided
additional consistency cues between the annotation and referent such as depth
(occlusion and motion parallax) and association (proximity). Labels were visible by
selection (default off).
Figure 3. Object Space vs. Viewport Space
Results Summary
Object vs. Viewport Space
The results of this experiment showed that overall the Viewport interface outperformed
Object space layouts on nearly all counts of accuracy, time, and ratings of satisfaction
and difficulty across tasks. In other words, for the set of tasks performed, tight-spatial
coupling of annotation to its referent (Object Space) was not as advantageous or
preferable as the consistent visibility provided by an image plane layout (Viewport Space).
This result suggests that the development and evaluation of a richer set of Viewport
Space layout capabilities (such as the X3D Compositing Component) would be
worthwhile. If the tight spatial coupling provided by Object Space layouts is deemed
necessary, consider further refining Object Space designs including managed or
emergent schemes (e.g. [19]).
Single and Nine-screen Configurations
Display size interacted with both Layout and SFOV variables for accuracy. The worst
performing combination was the Object Space with a high SFOV on a small display. The
best performing combination was the Viewport Space with high SFOV on a small display.
However, on the large display, high SFOV the Object Space outperformed the Viewport
Space.
With the tight spatial coupling, Object Space annotation schemes render the annotation
with the rest of the scene. Annotations end up on the image plane nearby their referentsthey provide the additional depth cues of occlusion and motion parallax and the additional
Gestalt association cues of proximity with their referents. We can postulate that the
advantage of the tight spatial coupling of Object Space only comes into effect when there
is enough screen size (DFOV) to avoid the occlusion problem. Also, on the large screen
size, tight spatial coupling means that users do not need to perform large saccades or
head movements to see and read the annotation.
In examining the transfer of the Viewport BorderLayout interface design across display
configurations, we can that say the successful transfer of an interface to a larger display
is not simply a matter of scaling. On the large display, our Viewport Space design had the
capacity for 3 times as many annotations. However on the large display, ergonomics
require special consideration. The BorderLayout Viewport Space annotations began in
the N container, which was above the line of sight at the top edge of the nine-screen
display. This made frequent reference fatiguing for users. There is substantial work to be
done in exploring Viewport Space annotation designs, especially for large displays. This
work suggests that design and management choices for image-plane-interface layouts
may be different depending on the size of the display.
Software Field of View
Our study results showed that overall our two SFOVs levels did not significantly affect
accuracy performance. However, higher SFOVs were advantageous for time especially
on search tasks, but negatively impacted accuracy especially on comparison tasks. This
result supports our hypotheses about the benefits of a high SFOV for search tasks (by
showing more of the scene in the periphery) and liability of a high SFOV for comparison
tasks (by distorting a scene object’s spatial location). It suggests that designers may
consider modifying the SFOV dynamically depending on the user task.
Conclusions 1
Reflecting on the implications of these results, we can answer our original hypotheses
and substantiate the following IRVE information design claims:

Overall, the guaranteed visibility of Viewport Space offered significant performance
and satisfaction advantages over the tight spatial coupling of Object Space annotation
layouts. The effect was
especially pronounced in the single-screen monitor
configuration.

The advantages of our Viewport Space layout did not transfer cleanly or scale isomorphically up to the larger nine-screen configuration. On the large display condition
for example, tight spatial coupling (Object Space) was more effective for accuracy
across tasks but especially for comparison.

Higher software FOVs decreased search time because they render more of the scene
in the projection. Higher software FOV increased spatial comparison times because of
fish-eye distortion. Consider modifying the SFOV per task.
Experiment 2 (Shupp et al)
We tested two different layout techniques and their support for IRVE Search and
Comparison tasks. All information was visible by default. The mapping of information type
for each task was also controlled. The techniques tested differed in their configuration of
views and represented opposite extremes of the occlusion/association design spectrum:
Object Space - embedded abstract info in the spatial info, tightly coupled:


was a single view visualization where all detail information was distributed in the
environment.
provided strong visual cues (gestalt and depth) for associating information with its
referent - high association, high occlusion.
Display Space - sibling abstract and spatial info, loosely coupled:


was a multiple view visualization where detail information was aggregated to
sibling attribute-centric visualizations. The attribure-centric views were linked
together.
had no visual or interactive association cues of abstract information to spatial
referent (no brushing and linking), only semantic (unique name of molecule) - low
occlusion, low association
Figure 4. Object Space vs. Display Space
The question we examined was:


"Under what task conditions is the single-view with tight spatial coupling of
Object Space advantageous over multiple, loosely coupled views of Display
Space"
or
"Under what task conditions is the cost of a structure/attribute context-switch
(with low association between information types) less than the benefit of no
context switch (high association between information types) ?"
The main hypothesis was that the high association of Object Space would be
advantageous for tasks where the criteria were spatial, but that the loosely coupled views
would be advantageous for tasks where the task criteria were abstract.
Results Summary
The following is a summary of conditions that have statistically significant effects per our
results:
Fastest Adjusted Time
o A  S in Display Space
Most Accuracy
o Search and A S in either technique
o Search and S  A in Display Space
o Compare and S  A in Object Space
o Compare and A S in Display Space
Most Satisfaction
o Display Space
o A  S in Display Space
Least Difficult for Task and 3D Navigation
o Search in Display Space
o A  S in Display Space
Conclusions 2
We can draw a few conclusions from this experiment.
The first derives from the fact that, contrary to the hypothesis, Display Space was
advantageous for a task where the criteria was spatial (Search: S->A ). This points to a
problem with the Object Space design as tested- the occlusion problem was managed
naively (by default, all labels were visible).
The second regards the fact that even with high occlusion and without an attribute-centric
visualization, the Object Space technique was better for Comparison: S->A accuracy.
This leads us to acknowledge that this layout technique is important to improve at least
for this task type (comparisons based on spatial criteria.
Finally, we can say that the benefits of additional attribute-centric visualizations with
reduced occlusion were stronger than the costs imposed by context switching between 2
visualizations of low association. …
To put this another way, the benefits of the tightly-coupled association in Object Space
were not sufficient to overcome the occlusion problem. In contrast, the Display Space
technique showed that the benefits of multiple views with no occlusion were sufficient to
overcome the costs of low association (context switching).
Gestalt x Depth cues provided by annotation Layout Spaces:
Tested Combinations
Object Space (Polys et al; Shupp et al)
None
Connectedness
Common
Fate
Similarity
Proximity
Common
Region
None
Occlusion
*
*
*
Motion
Parallax
Relative Size
/ Perspective
Binolcular
Disparity
*
*
*
Table 3
Viewport Space (Polys et al)
None
Connectedness
None
*
Common
Fate
*
Similarity
Proximity
Common
Region
Similarity
Proximity
Common
Region
Occlusion
Motion
Parallax
Relative Size
/ Perspective
Binocular
Disparity
Table 4
Display Space (Shupp et al)
None
Connectedness
None
Common
Fate
*
Occlusion
Motion
Parallax
Relative Size
/ Perspective
Binocular
Disparity
Table 5
Conclusions From Tested Combinations
From the first experiment, we can see that overall the Viewport Space was advantageous
over Object Space - the tight coupling (via Gestalt and Depth cues) provided by Object
Space was not advantageous enough to overcome the occlusion problem. However, the
tight-spatial coupling (via Gestalt and Depth cues) that is provided by Object Space was
advantageous for comparison tasks, especially when the display size was large and/or
the Software Field of View is high.
In the second experiment, we can see that the tight coupling (via gestalt and depth cues)
that is provided by Object Space is advantageous when the task mapping was
Comparison: S->A. However, on most other counts, a loosely coupled Display Space was
advantageous over Object Space - the loose coupling provided by Display Space was
more than compensated for by the minimal occlusion and the addition of attribute-centric
visualizations.
The research to date has helped to increase our understanding of the occlusion –
association tradeoff of IRVE design. What both of these experiments show is that there
are indeed tasks and situations where high association is advantageous enough to
overcome high occlusion (Object Space). However, overall, the benefits of minimal
occlusion (such as the Viewport or Display Space techniques tested) seem strong enough
to compensate for the costs of minimal association.
These results suggest that we should continue to refine our IRVE designs to mitigate the
occlusion – association tradeoff. Where task type and mapping suggests an
advantageous technique, we can focus on improving those respective techniques. For
example, finding better ways to reduce occlusion in Object Space and better ways to
increase association in Viewport and Display Spaces.
A. Selected publications (in chronological order).
1.
Brutzman, Don, Kass, Michael, Polys, Nicholas F. “X3D Content Examples, Editing,
Conformance Suite and Software Development Kit”. Sketches and Applications, ACM
SIGGRAPH 2001.
2.
Polys, Nicholas F. “Stylesheet Transformations for Interactive Visualization: Towards a
Web3D Chemistry Curricula”. Proceedings of the Web3D 2003 Symposium, ACM
SIGGRAPH. 2003.
3.
Bowman, D., North, C., Chen, J., Polys, N., Pyla, P., and Yilmaz, U. Information-Rich
Virtual Environments: Theory, Tools, and Research Agenda. in Proceedings of ACM Virtual
Reality Software and Technology. 2003. Osaka, Japan: ACM SIGGRAPH. 2003
4.
Polys, N. F., Duca, K. A., Laubenbacher, R., Bowman, D. A., North, C. “Interactive
Visualization of Biological Databases using Information-Rich Virtual Environments”, Poster.
Digital Biology: The Emerging Paradigm, NIH 2003.
http://staff.vbi.vt.edu/pathsim/NIHposter.pdf
5.
Polys, N., North, C., Bowman, D., Ray, A., Moldenhauer, M., Dandekar, C., “Snap2Diverse:
Coordinating Information Visualizations and Virtual Environments”. Visualization and Data
Analysis, International Society for Optical Engineering (SPIE) 2004.
6.
Polys, N., Bowman, D., North, C., Laubenbacher, R., Duca, K., “PathSim Visualizer: An
Information-Rich Virtual Environment for Systems Biology”. Proceedings of the Web3D
2004 Symposium, ACM SIGGRAPH 2004.
7.
Polys, Nicholas F., Bowman, Doug A., North, Chris. “Information-Rich Virtual
Environments: Challenges and Outlook”. NASA Virtual Iron Bird Workshop (Day 2, paper,
ppt & video), NASA Ames 2004.
8.
Polys, N., F., and Bowman, Doug A.. "Desktop Information-Rich Virtual Environments:
Challenges and Techniques." Virtual Reality 8(1): 2004, 41-54.
9.
Polys, Nicholas F. “Publishing Paradigms with X3D” In: Information Visualization with SVG
and X3D, (eds.) Chanomei Chen and Vladimir Geroimenko, Springer-Verlag, 2005.
10.
Polys, N.F., Duca, K.A., North, C., Bowman, D. , Laubenbacher, R. “Information-Rich
Virtual Environments for Biomedicine.” Poster. Computational Cell Biology, Lennox MA,
2005.
11.
MckCrickard, S., Wahid, S., Lee, J.,Polys, N. “Use and Reuse in Information and
Interaction Design” HCI-International 2005, Las Vegas, Nevada. LEA Associates. 2005.
12.
Polys, N. F., Kim, S., Bowman, D.A. “Effects of Information Layout, Screen Size, and Field
of View on User Performance in Information-Rich Virtual Environments” Proceedings of
ACM Virtual Reality Software and Technology 2005. Monterrey, CA: ACM Press. 2005.