Exploring large virtual environments, such as cities, is a central task in several domains, such as gaming and urban planning. VR systems can greatly help this task by providing an immersive experience; however, a common issue with viewing and navigating a city in the traditional sense is that users can either obtain a local or a global view, but not both at the same time, requiring them to continuously switch between perspectives, losing context and distracting them from their analysis. In this article, our goal is to allow users to navigate to points of interest without changing perspectives. To accomplish this, we design an intuitive navigation interface that takes advantage of the strong sense of spatial presence provided by VR. We supplement this interface with a perspective that warps the environment, called UrbanRama, based on a cylindrical projection, providing a mix of local and global views. The design of this interface was performed as an iterative process in collaboration with architects and urban planners. We conducted a qualitative and a quantitative pilot user study to evaluate UrbanRama and the results indicate the effectiveness of our system in reducing perspective changes, while ensuring that the warping doesn't affect distance and orientation perception.

Large scale shadows from buildings in a city play an important role in determining the environmental quality of public spaces. They can be both beneficial, such as for pedestrians during summer, and detrimental, by impacting vegetation and by blocking direct sunlight. Determining the effects of shadows requires the accumulation of shadows over time across different periods in a year. In this paper, we propose a simple yet efficient class of approach that uses the properties of sun movement to track the changing position of shadows within a fixed time interval. We use this approach to extend two commonly used shadow techniques, shadow maps and ray tracing, and demonstrate the efficiency of our approach. Our technique is used to develop an interactive visual analysis system, Shadow Profiler, targeted at city planners and architects that allows them to test the impact of shadows for different development scenarios. We validate the usefulness of this system through case studies set in Manhattan, a dense borough of New York City.

Cities are inherently dynamic. Interesting patterns of behavior typically manifest at several key areas of a city over multiple temporal resolutions. Studying these patterns can greatly help a variety of experts ranging from city planners and architects to human behavioral experts. Recent technological innovations have enabled the collection of enormous amounts of data that can help in these studies. However, techniques using these data sets typically focus on understanding the data in the context of the city, thus failing to capture the dynamic aspects of the city. The goal of this work is to instead understand the city in the context of multiple urban data sets. To do so, we define the concept of an "urban pulse" which captures the spatio-temporal activity in a city across multiple temporal resolutions. The prominent pulses in a city are obtained using the topology of the data sets, and are characterized as a set of beats. The beats are then used to analyze and compare different pulses. We also design a visual exploration framework that allows users to explore the pulses within and across multiple cities under different conditions. Finally, we present three case studies carried out by experts from two different domains that demonstrate the utility of our framework.

There is a growing expectation for high performance design in architecture which negotiates between the requirements of the client and the physical constraints of a building site. Clients for building projects often challenge architects to maximize view quality since it can significantly increase real estate value. To pursue this challenge, architects typically move through several design revision cycles to identify a set of design options which satisfy these view quality expectations in coordination with other goals of the project. However, reviewing a large quantity of design options within the practical time constraints is challenging due to the limitations of existing tools for view performance evaluation. These challenges include flexibility in the definition of view quality and the ability to handle the expensive computation involved in assessing both the view quality and the exploration of a large number of possible design options. To address these challenges, we propose a catalogue-based framework that enables the interactive exploration of conceptual building design options based on adjustable view preferences. We achieve this by integrating a flexible mechanism to combine different view measures with an indexing scheme for view computation that achieves high performance and precision. Furthermore, the combined view measures are then used to model the building design space as a high dimensional scalar function. The topological features of this function are then used as candidate building designs. Finally, we propose an interactive design catalogue for the exploration of potential building designs based on the given view preferences. We demonstrate the effectiveness of our approach through two use case scenarios to assess view potential and explore conceptual building designs on sites with high development likelihood in Manhattan, New York City.