Take a deep breath; what do you smell? While sight and hearing dominate our perceptions, the sense of smell is often overlooked, even undervalued. However, the importance of our sense of smell goes beyond detecting odours. It shapes our emotions, memories, behaviour, and quality of life. Recent advances in olfactory interfaces have sparked discussions about the future of smell in human-computer interaction. While efforts mainly focus on the realization of new olfactory interfaces, here we collectively explore alternative worlds centred around the sense of smell. First, we conducted a design futuring workshop involving individuals with varying smell capabilities and expertise to envision and discuss smell-centred futures. Then, through iterative reflection, we arrived at three smell worlds presented as narratives and visuals. From this conceptual work, we offer new perspectives and generative possibilities for design research that prioritizes our noses.

Urban media interfaces can assume many forms, offering rich possibilities for interactions and social encounters. We focus on a particular type of urban interfaces, namely urban media installations, which are situated, fixed (i.e. non-mobile) and outdoor interactive interfaces enhanced by digital technologies. Drawing on research on play in the context of the smart city, we aim to clarify how the digital and the physical worlds of urban media installations can coalesce into enjoyable and socially thriving playscapes. Two case studies of urban media installations are presented: the Appearing Rooms, a seasonal art installation in London, and the Mirror Pool, a permanent, large-scale urban installation in Bradford, UK. Each of these interfaces incorporates a design paradigm that differs from the other in terms of context, duration of implementation, and scale. Following a longitudinal approach based on non-participant observations and time-lapse photography, we analyse emergent interactions and focus in particular on playful encounters at different levels and scales: from the micro scale of the bodily engagement to the macro scale of the spatial and social configurations. Our case studies highlight that the urban spatial layout is a key element in defining the emerging interactions and encounters around the urban situated interfaces.

In this paper we investigate human interactions with urban media installations by adopting two scales of analysis: the body scale (micro) and the city scale (macro). This twofold approach allows us to better understand the relationships between the design properties of outdoor installations and the urban spatial layout around them. We conducted in-the-wild studies of two urban media installations, one consisting of fixed components, and the other of movable components, which were deployed in different places and encouraged different types of whole-body interaction. We provide a detailed account of the micro and macro levels of interactions, based on observational and qualitative explorations. Our studies reveal that the urban spatial layout is a key element in defining the interactions and encounters around outdoor interfaces, and therefore it needs to inform the design process from the outset.

Overlaying a building with images from the past can be an engaging way to explore a historic site. However, little is known about what type of content functions well when using augmented reality (AR) in outdoor contexts. This research investigates how different types of AR content – such as text or image – can affect the flow experience as well as other user affective and behavioural responses. We ran an experimental study with 85 participants at a university campus, where three groups used different apps – AR app with overlaid textual information, AR app with overlaid both textual information and images and an app with audio guide – to explore the area's historic and cultural background. The results show that overlaying images in addition to the text was clearly the most successful way of attracting attention and providing stronger flow in comparison to the apps that overlaid only text or delivered audio. However, we also discovered that users occasionally interpreted the overlaid imagery to be cues for something else other than what they were designed to represent. Finally, we discuss how AR content can enlarge otherwise invisible details, depict historic elements and unveil interiors of buildings.

Buildings and urban spaces increasingly incorporate artificial intelligence and new forms of interactivity, raising a wide span of research questions about the future of human experiences with, and within, built environments. We call this emerging area Human-Building Interaction (HBI) and introduce it as an interdisciplinary domain of research interfacing Human-Computer Interaction (HCI) with Architecture and Urban Design. HBI seeks to examine the involvement of HCI in studying and steering the evolution of built environments. Therefore, we need to ask foundational questions such as the following: what are the specific attributes of built environments that HCI researchers should take into account when shifting attention and scale from “artefacts” to “environments”? Are architecture and interaction design methods and processes compatible? Concretely, how can a team of interaction designers bring their tools to an architectural project, and collaborate with other stakeholders? Can and will architecture change the theory and practice of HCI? Furthermore, research in HBI should produce knowledge and practical guidelines by experimenting novel design instances that combine architecture and digital interaction. The primary aim of this article is to specify the mission, vision, and scope of research in HBI. As the introductory article to the TOCHI special issue, it also provides a summary of published manuscripts and describes their collective contribution to the development of this field.

Urban screens are becoming a common element of our city landscape. As such they offer new ways of connecting people that occupy public space, e.g., by taking situated snapshots through a display-attached camera. In this paper we present a first longitudinal case study of 12 weeks of such an application -- Moment Machine -- deployed "in the wild" on an urban screen facing the street. We report findings from 1189 photos taken, 13 interviews, and 3 weeks of observations that show engagement stimulated by situated snapshots within a place-based community where the screen is located. We also analyze interaction log files to describe how often users interacted, what type of interactions they had and how long they lasted, and overall engagement on a weekly basis and throughout the week. Based on our experience, we provide three take-away snippets for designers of similar urban screen experiences.