Teaching:TUW - UE InfoVis WS 2008/09 - Gruppe 01 - Aufgabe 1 - Visual Encoding

Visual Encoding

Definition

Visual encoding is the set of techniques enabling the representation of data on a screen or on paper. It comprises of the use of shapes, colours, areas and other visual variables that make it possible to associate data variables to graphic variables [Dürsteler, 2005]. Visual encodings are mappings of information to display elements [Munzner, 2000].

Techniques of Visual Encoding

The fundamental substrate of visualizations is spatial position. Marks such as points, lines, or area-covering elements can be placed on this substrate. These marks can carry additional information independent of their spatial position, such as size, greyscale luminance (brightness) value, surface texture density, color hue, color saturation, curvature, angle, and shape [Munzner,2000].

• Space
• Marks
• Connections & Enclosures
• Retinal Properties
• Temporal Encoding
• Viewpoint Transformation

Space

When you think about an empty paper as the beginning of a visualisation, the space between some possible object is one of the most powerful aspects to give something an important note.

Marks

Marks are the visible things that occur in space [Jacko], and are simply any graphical symbol visible on a display medium[Ignatius,Eve&Senay,Hikmet]. There are four types of simple Marks :

• Points
• Lines
• Areas
• Volumes

Connections & enclosures

Connections and enclosures build the important dependencies between the objects (marks). Connections show a relationship between objects, while enclosures can also indicate related objects.

Retinal properties

A retinal encoding is any variation of the marks that the retina of the eye can perceive besides position [Ignatius,Eve&Senay,Hikmet]. They are the informations that are carried by marks, such as crispness, shape, resolution, transperancy, color(value,hue&saturation), grayscale[Munzner, 2000]. Retinal properties describe how objects (marks) look like.

Abbildung S. 30 von Readings in Information Visualization

[Card] Retinal properties

Temporal encoding

A temporal encoding shows how the marks' properties vary over time [Ignatius,Eve&Senay,Hikmet].

It's the encoding which depends on the temporal changes of marks (mark position and their retinal properties). [ todo : Source ]

Viewpoint transformations

Viewpoint transformations modify interactively and augment Visual Structures to turn static presentations into visualizations by establishing graphical parameters to create Views of Visual Structures [Card], in other words it is the modification of the view position of the viewer (or in general the modification of viewing parameters), thus enhancing the visual perception.

There are three common view transformations :

• Location Probes : Usage of Location in the visual structures to reveal additional info
• Viewpoint control : Moving the viewpoint to create visualisation : Pan,zoom,clip the viewpoint.
• Distortion : Creating a focus area and context area.

References

• [Dürsteler, 2005] Web Content Mining Visualisation , EN:http://www.infovis.net/printMag.php?num=175&lang=2
• [Munzner,2000] Interactive Visualization of Large Graphs and Networks, EN: http://graphics.stanford.edu/papers/munzner_thesis/
• [Card,1999] Readings in Information visualization : Using vision to think, EN: http://books.google.com/books?id=wdh2gqWfQmgC/
• [Ignatius,Eve&Senay,Hikmet] Data,vocabulary,marks,composition rules and visual perception rules, EN: http://cose.math.bas.bg/Sci_Visualization/visConcepts/concepts/marks.htm
• Julie A. Jacko, Andrew Sears, 2003, The Human-computer Interaction Handbook: Fundamentals, Evolving Technologies
• Readings in Information Visualization Von Stuart K. Card, Jock D. Mackinlay, Ben