Shape-changing displays typically lose pixel density as surface area expands, limiting their usability. We introduce MorphSkein, a shape-changing after-image display that preserves initial density (1.44 px/cm 2 ) across naturally occurring axisymmetric shapes generated by spinning cables (troposkeins). The system uses a telescopic pole and four LED-strip rewinders on a rotating base. As the strips spin, centrifugal force forms troposkeins, and persistence of vision creates 360°-visible displays, while adjusting pole height and strip lengths changes their shape. As surface area grows, pixel density is preserved vertically by releasing new rows from the rewinders and horizontally by rendering extra columns per revolution with the strips. This keeps comparable density along the central horizontal line of the display, with naturally higher density toward the top and bottom where the troposkein curves inward. Because the technique relies on a mathematical model assuming ideal troposkein geometry, angular velocity becomes critical: incorrect speeds degrade pixel density accuracy, axisymmetric shape fidelity, or both. Interpolation of experimental data shows that 69.44% of reachable troposkein configurations achieve ⩾90% density accuracy and shape fidelity for at least one operating speed. Remaining cases degrade due to insufficient motor speed or limited MCU speed and LED refresh rate. Limitations and improvements are discussed.

International audience

International audience

In the last decade, HCI research has proposed promising technologies for shape-changing interfaces. The usefulness and the user experience of shape-change are, however, still to be explored and understood. This paper extends the understanding of the potential utility and usability of axisymmetric shape-change. First, we present 16 potential use cases for a cylindrical shape-changing display. Second, we present a two-month comparative field study in the workplace. Six participants had to shift energy consumption by using energy storage. To do so, they were notified about local energy forecasts. Compared with flat-screen animations, early results show that cylindrical shape-change animations keep a better attractiveness over time.

We present CairnFORM, a shape-changing cylindrical display that physicalizes forecasts of renewable energy availability. CairnFORM aims at creating and encouraging new socially-shared practices by displaying energy data in collective and public spaces, such as public places and workplaces. It is 360°-readable, and as a dynamic physical ring chart, it can change its cylindrical symmetry with quiet motion. We conducted two user studies. The first study clearly revealed the attractiveness of CairnFORM in a public place and its usability for a range task and for a compare task. Consequently, this makes CairnFORM useful to analyze renewable energy availability. The second study revealed that a non-constant motion speed is the better visualization stimulus at a workplace.

Data physicalizations are growing popular in many societal domains which indicates a strong potential for fostering public engagement thanks to public exhibition (e.g. in train stations, in airports, on roundabouts, and in enterprises). We focus on dynamic physical charts for visualizing renewable energy forecasts in public spaces. To get charts readable from any point of view around, we propose a physical ring chart inspired by stone cairns. To build this physical chart, we designed an expandable and stackable illuminated ring. In this paper, we describe the design process and the limitations of the first prototype of such a ring.

Measuring brain activity with electroencephalography (EEG) is mature enough to assess mental states. Combined with existing methods, such tool can be used to strengthen the understanding of user experience. We contribute a set of methods to estimate continuously the user's mental workload, attention and recognition of interaction errors during different interaction tasks. We validate these measures on a controlled virtual environment and show how they can be used to compare different interaction techniques or devices, by comparing here a keyboard and a touch-based interface. Thanks to such a framework, EEG becomes a promising method to improve the overall usability of complex computer systems.