INFORMATION VISUALIZATION ON SPHERES - Information Visualisation: Techniques, Usability and Evaluation - page 39

• Interactive techniques could be made to transform dynamically
between a flat projection and a spherical projection.
• Sparse visuals on the sphere provide an ability to see through the
sphere, although this can create issues when attempting to perceive
data at varying depths.
• Hidden data or visual hints to data on the reverse side could
potentially be useful, for example, as a narrative device to reveal
data incrementally.
Perception and Occlusion : With spheres, as with any 3D information
visualization, care must be taken to ensure ease of perception. Excessive
layering, occlusion, or overlapping impedes comprehension. Techniques
that improve depth perception can potentially help, such as depth shading
(i.e. fog), outlines and auto-rotation, although the last of these did
introduce new perception issues.
Interaction Models : While a virtual trackball provides intuitive scene
navigation, click and drag selection was no longer available and was an
expected interaction from one user. Other expected interactions may need
to be accommodated via modes, manipulators or other techniques.
Extra Development Effort : Maintaining distances, areas and
viewpoints requires extra development effort.
Conclusions
Feedback illustrates that sphere-based visualizations can be applied
successfully to some applications. The experiments also show that there
are a number of potential issues using spheres that need to be addressed
and alternative organizations should be considered.
Spheres offer a unique paradigm for applications where user mental
models have the notion of items that are inverse or flipped. Spheres also
offer a wrap-around surface. Note that wrap-around surfaces can also be
achieved and depicted on a 2D plane including projections of spheres and
tori (e.g. [Ito00]), similar to flat map projections and video games.
However, 2D wraparound may be evident only while animated, whereas a
sphere's wrap-around structure is evident whilst static. This could be
investigated as an alternative.
Other avenues of exploration include interactive flattening of a sphere
into a projection (e.g. Mercator projection), use of an internal viewpoint,
and other interaction techniques to overcome limitations.