Temporal Treemaps: Static Visualization of Evolving Trees

2018 IEEE Transactions on Visualization and Computer Graphics  
We consider temporally evolving trees with changing topology and data: tree nodes may persist for a time range, merge or split, and the associated data may change. Essentially, one can think of this as a time series of trees with a node correspondence per hierarchy level between consecutive time steps. Existing visualization approaches for such data include animated 2D treemaps, where the dynamically changing layout makes it difficult to observe the data in its entirety. We present a method to
more » ... isualize this dynamic data in a static, nested, and space-filling visualization. This is based on two major contributions: First, the layout constitutes a graph drawing problem. We approach it for the entire time span at once using a combination of a heuristic and simulated annealing. Second, we propose a rendering that emphasizes the hierarchy through an adaption of the classic cushion treemaps. We showcase the wide range of applicability using data from feature tracking in time-dependent scalar fields, evolution of file system hierarchies, and world population. Manuscript received xx xxx. 201x; accepted xx xxx. 201x. Date of Publication xx xxx. 201x; date of current version xx xxx. 201x. For information on obtaining reprints of this article, please send e-mail to: reprints@ieee.org. Digital Object Identifier: xx.xxxx/TVCG.201x.xxxxxxx It is particularly useful to associate data to the nodes of a tree. Different methods can then be used to reveal the largest or smallest parts of the hierarchy. The concept of nested layouts, in particular treemaps [28] , is a wide-spread visualization approach for such trees. Data associated with a tree may change over time and it is of high interest to observe the temporal development of this data. Dynamically adjusting treemaps [19, [30] [31] [32] [33] 37] have been proposed for this. Furthermore, stream graphs enhanced with hierarchical information [3, 14, 40] provide a static overview of the entire temporal development of trees with dynamically changing data. This paper deals with trees whose data and topology change over time. Essentially, the entire tree can transform almost arbitrarily as long as it remains a tree. To be precise, we consider a time series of trees with a node correspondence per hierarchy level between consecutive time steps. Tree nodes may appear and disappear, merge and split on all This is the author's version of an article that has been published in this journal. Changes were made to this version by the publisher prior to publication. The final version of record is available at http://dx.
doi:10.1109/tvcg.2018.2865265 pmid:30137007 fatcat:w4etu7jxiba3fa7dhbvghnqi3e