Information visualization encodes data attributes with visual variables such as position, color, size or shape. In dynamic visualizations, variables may change over time, reflecting changes of the underlying data attributes. Visual variables are not necessarily static: motion can also be used to encode a data attribute. Animation, as a means to encode data characteristics, can be broken down into four roles.
Revealing data relationships
Animation is commonly used to show how data changes and evolves over time, or over other non-temporal dimensions such as age or income.
A famous example is Gapminder which animates a scatterplot showing country statistics of birth rate and life expectancy, allow users to see how the world has changed over 2 centuries. Users can simply play the animation or control the advance step by step and see the correlations in the data. Trails can be left behind the data points.
Causality is another example of data relationships that animation is particularly good at conveying.
Ware, C., Neufeld, E. and Bartram, L. (1999). Visualizing Causal Relations. In IEEE Information Visualization Proc. Late Breaking Hot Topics, 39-42.
An early cartographic application showed how rainfalls location affects forest growth through animation.
Blok, C., Kobben, B., Cheng, T. & Kuterema, A. (1999) Visualization of relationships between spatial patterns in time by cartographic animation. Cartography and Geographic Infor-mation Science 26(2):139–151.
Zaman, L., Kalra, A. and Stuerzlinger, W., 2011, May. DARLS: differencing and merging diagrams using dual view, animation, re-layout, layers and a storyboard. In CHI'11 Extended Abstracts on Human Factors in Computing Systems (pp. 1657-1662). ACM.
Robertson, G., Cameron, K., Czerwinski, M. and Robbins, D., 2002, April. Polyarchy visualization: visualizing multiple intersecting hierarchies. InProceedings of the SIGCHI conference on Human factors in computing systems (pp. 423-430). ACM.
Andrienko, N. and Andrienko, G., 2004, May. Interactive visual tools to explore spatio-temporal variation. In Proceedings of the working conference on Advanced visual interfaces (pp. 417-420). ACM.
Craig, P., Kennedy, J. and Cumming, A., 2005. Animated interval scatter-plot views for the exploratory analysis of large-scale microarray time-course data.Information Visualization, 4(3), pp.149-163.
Conveying uncertainty or randomness
Animation has been used to represent randomness or uncertainty by moving objects on the screen in a random way over the range of possible values.
Cancer risk has been represented as an array of 100 icons, with 9 of them dark, but some users wrongly interpret the display and believe that they have a 0% or 100% chance of developing cancer. Animation has been used to enhance the representation of randomness by changing the position of the dark icons every 2 seconds. Similarly, animation has been used to indicate uncertainty by wiggling the position of points or bounda-ries on maps or other visualizations.
Han, P., Klein, W., Killam, B., Lehman, T., Massett, H. & Freeman, A. (2011). Representing randomness in the commu-nication of individualized cancer risk estimates: Effects on cancer risk perceptions, worry, and subjective uncertainty about risk. Patient Education and Counseling, 83(1).
Particular motions can be used to convey stereotypic emotions.
The fact that motion is a good proxy for emotion has been known for long in traditional animation: “When you take something that's inert, and through motion, give it life, make it appear to be alive, living, breathing thinking and having emotions, that's animation.”. Perlin has explored different emotion expressions with Polly, a 5-polygon prism that walks around a surface (http://mrl.nyu.edu/~perlin/polly/). Different behaviors, like e.g. feeling dejected, can be assigned to Polly, which affects the prism’s gait. This small application very nicely illustrates how motion can affect perceived emotion. Yet, it is just a prism!
Animated fonts is an animation of letters that enable to convey of the meaning of the word (e.g. letters of the word “jump” jump), enhancing the reading experience for a young audience.
Wang, H., Prendinger, H. and Igarashi, T., 2004, April. Communicating emotions in online chat using physiological sensors and animated text. InCHI'04 extended abstracts on Human factors in computing systems (pp. 1171-1174). ACM.
Encoding object attribute
Motion can be used to encode different attributes of visual objects, in particular, different categories. It can then be used for filtering and brushing.
Bartram, L., Ware, C., & Calvert, T. (2003). Moticons: detec-tion, distraction and task. International Journal of Human-Computer Studies, 58(5), 515-545.
When reordering a priority traffic list with Mobilistes, list items are moved using an animated trajectories that is specific to the type of mode of transportation (bus, car or plane).
Schlienger, C., Dragicevic, P., Ollagnon, C., & Chatty, S. (2006). Les transitions visuelles différenciées: principes et ap-plications. In Proc. IHM, 59-66.
In motion pointing, each visual item of the interface such as a push-button or radiobutton has a driver i.e. an animated point displayed on top of it and playing a unique cyclic elliptical movement. To select a specific item, the user has to imitate the motion of its driver using the input device and mimicking that motion (i.e., shape of trajectory, frequency, phase, amplitude, etc.)
Fekete, J.D., Elmqvist, N. and Guiard, Y. (2009). Motion-pointing: target selection using elliptical motions. In Proc. CHI’09, 289-298.
Johansson, J., Ljung, P., Jern, M. and Cooper, M., 2005, October. Revealing structure within clustered parallel coordinates displays. In Information Visualization, 2005. INFOVIS 2005. IEEE Symposium on (pp. 125-132). IEEE.
Andrienko, N., Andrienko, G. and Gatalsky, P., 2000, May. Supporting visual exploration of object movement. In Proceedings of the working conference on Advanced visual interfaces (pp. 217-220). ACM.