Geoscience Reference
In-Depth Information
TABLE 5.1
Brief Summary of Key Visualisation Terms Used throughout This Chapter
Term
Meaning in This Text
Data attribute (data,
variable)
Data (numerical or textual) from a database or GIS. A data attribute is a unique,
single-valued field in a database, such as population density or soil type.
Visual variable (visual
attribute, retinal variable)
Visual
data
, encoded in some property of a symbol or other visual device; its value is usually
derived from some kind of transformation (see visual encoding) applied to real data.
Display (view, plot, graph,
window)
A specific arrangement of symbols and graphing metaphors to create a visualisation tool, for
example, a map, scatterplot or 3D geological model.
Scene (visualisation)
Any number of displays, coordinated together in a single session or
experiment
.
Pop-out
A coherent, discernible visual signal or pattern in a display that gets noticed by the user.
Visual encoding
The transformation of numerical and textual values in data to a visual form, via some kind of
transformation function, such as a colour ramp.
Symbol (glyph, geometric
mark)
Some geometric device, such as a circle or arrow, capable of supporting several visual
variables (e.g. using colour, size and transparency).
primarily designed for scientific and engineering uses and could render objects in 3D, from any
viewpoint, and using sophisticated models of surface lighting, material reflectance and ray trac-
ing (Palamidese, 1993), to give lifelike realism to rendered objects - whether they were car parts,
buildings or faces. This approach became known as SciViz and still has a strong presence in both
research and practice. Figure 5.3 shows an example of a scene under construction in a SciViz
system, with controls for scene lighting and surface reflectance properties positioned alongside a
variety of other controls.
On a somewhat parallel evolutionary path, InfoViz first emerged as a supplementary aid to statis-
tical analysis (e.g. Cleveland and McGill, 1988) and mostly in ad hoc systems and tools developed
by researchers. The focus has moved over time from developing new charting tools (such as parallel
coordinate plots: Inselberg, 1997), to rich coordination strategies over multiple displays (Weaver,
2004), to tools supporting node-edge style graphs, to geographical visualisation and finally moving
the visualisation tools to the web (working directly from a web browser). The InfoViz community
has seen very rapid growth in the last few years and exerts the strongest influence currently on
GeoViz. A truly formidable range of tools and systems are now available (see http://www.infovis-
wiki.net/index.php?title=Toolkit_Links for a comprehensive list), some of which can support the
visualisation of geographical information. The InfoViz community tends towards an open-source
ethos, so can be an excellent source of tools and related information.
Finally, and more recently, there has been a trend towards specialised software systems to sup-
port the production of animated content. These systems became popular in the late 1990s with
the emergence of
Flash
as a simple desktop tool with which to create animations by scripting the
behaviour of symbols and backdrops. These too can have a role in GeoViz (e.g. Bhowmick et al.,
2008). More complex versions of these systems, such as
Maya
and
Blender
,*
are used extensively
in the design and movie industries to render complex objects and environments with such lifelike
detail that they can pass for real.
To summarise the previous condition, SciViz systems usually offer the most control over visual
appearance and can define arbitrarily complex geometry and provide fly-throughs and advanced
lighting methods to create visual realism (such as scene illumination). InfoViz systems offer
the most comprehensive sets of graphing methods, often with powerful, pre-built coordination
*
A useful list of 3D animation software systems is available on Wikipedia at http://en.wikipedia.org/wiki/
List_of_3D_animation_software.
