Un/foldables are interactive visualization mechanisms that reveal or reduce information through fluid transformations such as compression, expansion, or deformation in a focus region while maintaining the overall context.
Revealing relevant information on demand is an essential requirement for visual data exploration. This project is a state-of-the-art report, where we review and classify techniques that are inspired by the physical metaphor of un/folding to reveal relevant information or, conversely, to reduce irrelevant information in data visualizations. Given its beneficial effect on space efficiency, un/folding is a recurring theme across nature, engineering, and design.
![Sketches derived from examples of un/folding in nature and engineering [Mol01, HV17], showing from left to right three states of a hand fan, an origami, a flower blossom, an accordion, a Swiss army knife, a pufferfish, and an umbrella.](https://uclab.fh-potsdam.de/media/pages/projects/un-foldables/54e077981e-1751307589/unfolding-in-nature-1700x.webp)
Similar to focus+context approaches, un/foldable visualizations transform the visual data representation, often between different granularities, in an integrated manner while preserving the overall context. This typically involves switching between different visibility states of data elements or adjusting the graphical abstraction linked by gradual display transitions.
In total, we collected a corpus of 101 un/foldable visualizations, according to four characteristics. We consider approaches that (1) involve revealing or reducing information on demand, (2) integrate seamlessly into a base visualization, (3) preserve the overall visualization context, and (4) follow the idea of fluid interaction.
We derive a classification scheme to characterize collected approaches with respect to seven aspects of un/folding:
– Data facets: What types of data are un/folded?
– Focus scope: How much is actually un/folded?
– Effect scope: To what extent is the visualization affected?
– Unfolding scale: How many un/folding states exist?
– Transformation type: What type of transformation is used?
– Transition control: How can the un/folding be controlled?
– Interaction directness: How direct is the interaction?
Finally, based on the book "Collapsibles – A Design Album of Space-Saving Objects" by Per Mollerup, we further group un/folding techniques into families that share common transformation mechanisms. We use metaphors drawing from physical mechanisms that gradually expand, compress, or deform the shape of an object: Assembling, Fanning, Folding, Hinging, Inflating, Nesting, Scrunching, Sliding, Stacking, and Stretching.
The collection of un/foldables is available as an online catalog that includes classic focus+context, semantic zooming, and multi-scale visualizations as well as contemporary un/foldable visualizations.