Data Physicalizations

Data physicalization evolved from areas such as visualization [22] and tangible user interfaces [71, 74] as a form of data analysis in physical form. They embody physical artefacts whose geometry or material properties encode data [3, 81]. Calvert et al. [21] highlight that humans have evolved a highly complex sensory system that allows them to efficiently extract information from the physical world. Representing data through interactive physical objects enhances the identification and interpretation of sensory information beyond the capabilities of flat displays.

Encoding data into physical artefacts where geometry or material properties convey meaning or represent data patterns has long-standing practice and tradition in both scientific and design communities [31]. From the early Mesopotamian Clay Tokens (5500 BC) [31] to Durrell Bishop’s first tangible user interface (1992) the Marble Answering Machine [74]. With the recent convergence of digital fabrication, tangible

27 interfaces, and shape-changing displays the emergence of data physicalization as an independent area is becoming increasingly clear [3, 81].

Computer-supported physical data representation enhances the understanding, exploration, and communication of data [80]. As a result, comprehensive and engaging user experience is available. This is beyond the capabilities of conventional applications of flat, rigid, and static surfaces. Physicalizations enable people to perceive data by leveraging their internal sense of physical space and ability to manipulate objects. They utilise spatial perception, where physical objects can provide enhanced cues of shape and volume to represent data in a 3D form, ensuring the data can be perceived with less effort and more accuracy than on a computer display [81], even stereoscopic displays [80].

There is an opportunity to develop a wide range of novel interaction capabilities from new forms of data representations. With current innovation and development of shape- changing displays, complex data analysis tasks performed by existing desktop computers could also soon be enhanced through data physicalization systems. The representation of data through physical artefacts has also potential to be extended beyond traditional visualisations of numeric data and bar charts [80, 81]. The representation of data as physical artefacts also supports cognitive and sensory stimuli [31].

Although the majority of physicalizations developed currently are static, they can still offer perceptual, cognitive, and communicative stimuli as well as enhance user experience value which could not be possible through desktop computers. Current work has already established processes for composing and creating one-off static physicalizations, using fabrication technologies [171, 173]. Dynamic physicalizations in comparison require additional computer driven control of physical geometry or material properties. A wider range of techniques for actuation has been explored and implemented for controlling physical geometry both for data physicalizations and shape-changing interfaces [138, 143].

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Figure 4: Examples of Data Physicalizations.

Data physicalizations come in many forms as seen in Figure 4. Jansen et al. [80] show

3D physical bar charts where datasets can be switched by hand (Figure 4A).

Cylinder by Andy Huntington and Drew Allan [66] is an early example of digitally- fabricated sound sculptures (Figure 4B). Physicalizations can also represent data in

more abstract and artful forms. Work by data artist Doug McCune [105] depicts a 3D printed map of housing prices in San Francisco Figure 4C in abstract form. The height

of each area represents the average price per square foot for recent home sales. A more realistic physical representation of topographical data can be seen by Pristnall et al. [134]. The PRAM system is a static physical relief model is augmented with top projection to display landscape details and to overlay with additional data visualizations

Figure 4D. Work by Richard Burdett [17] demonstrates larger scale data

physicalizations to represent density models where plywood forms embody the populations of 12 of the world’s major urban centres (Figure 4E).

Many physicalizations focus on a direct mapping between the data and representations. Specifically, when exploring and evaluating engagement with users’ personal data. Physikit [64] is a toolkit and technology probe [67] that maps users’ data about their home energy consumption into physical data representations in the form of tangible cubes. This work encourages end-user to programme their own physical data representations in the realm of the internet of things (IoT). Ananthanarayan et al. [8] have also proposed a novel approach to represent personal health by using paper cherry

29 blossom leaves, flowers, or felt and Velcro stick-objects. From personal quantitative data to qualitative emotional data representations, Emoballoon [116] is a soft social- touchable interface that can monitor human intentions or emotions based on touch interaction. These interactions include hugging, rubbing, and slapping using a series of sensors within a balloon. Visually communicating emotion has thus far been predominately studied in colour theory [124]. Initial work within HCI [163] evaluates how physical shape configurations are used to represent emotionality for users. These explorations of information representations through physical forms [4, 176] enhance understanding of which data is best conveyed through the representation of shapes to users in a range of contexts.

Jansen et al. [81] highlight the need to better support interaction with physical forms. Their initial review encourages the development of techniques for the empirical evaluation of data physicalizations. They also emphasize that more generalised approaches for the design and fabrication of data physicalizations must emerge to ensure wider range applications can be supported. Empirical evaluation techniques could also highlight the trade-offs between cost and utility. Currently, projects within the field of data physicalizations are isolated within specified domains. However, by developing a generalizable evaluation framework results can become comparable. These evaluations need to be comparable across a wide range of systems. As the field is still immature, no generalised empirical evaluation methodology has been considered comprehensively. This is in part due to the majority of current work focusing on isolated instances and as a result, there is a lack of a broad overview of data physicalization. A similar paradigm is also lacking in the domain of shape-changing displays. This could be partially due to the limited generalisability of tangible systems that go beyond singular sentences, an issue this thesis aims to address. By contrast, in other domains such as digital signage [7] or web usability [117-119] evaluation challenges are well understood.

Given the recent increase in research interest addressing this topic, it is anticipated that there will be a need to perform evaluations of the effectiveness of communicating data, aesthetics, and efficiency to establish fundamental guidelines of designing and developing data physicalizations. In terms of technical capabilities with existing and impending advances in digital fabrication, shape-changing displays [57, 138], tangible user interfaces [155], and programmable materials [71, 74] it is now possible to create

30 data physicalizations faster, cheaper, and more effectively than before by utilising existing tools [57]. However, this stands more towards static applications for data physicalizations that at best can only be manually deformed. The fabrication of dynamic materials and surfaces to support physical movement and form reconfigurations for displays is still limited. The need to create more dynamic display surfaces that can be computationally reconfigured is still a technical challenge that requires high costs [6]. As it stands with current applications, it must be considered if the benefits of creating data physicalizations outweigh the cost of design and fabrication.