4D Data Visualization Using Iso-surfaces and a Control Plane

Many areas of science and engineering rely on our ability to efficiently analyze large data sets from a four-dimensional (4d) space-time domain. These data sets represent the evolution through time of quantities such as temperature, pressure, and flow velocity that are measured or computed on a dense set of sample points in three-dimensional (3d) space. At a high-performance computing center (HPCC), full-scale simulations of atmospheric turbulent flow or a combustion in an engine produce hundreds of gigabytes of data. Often, preselected 2d slices or 2d iso-surfaces in 3d are downloaded from the HPCC to visualize such data sets; if a researcher suspects that a different slice will show a phenomenon of interest, he or she must download and manipulate data locally, or rerun the entire simulation. Researchers would benefit from an efficient interactive remote access to simulation data, but limited bandwidth is a bottleneck. Increases in bandwidth, processing, and storage are not likely to eliminate this problem because they also increase the size of data sets produced. We are investigating a client-server architecture for interactive remote analysis based on partitioning the data dimensions. A visualization server stores data on an adaptively simplified 4d mesh of the domain, and a client views an iso-surface in a 3d volume by selecting a particular time and iso-value. Time and iso-value form a 2d-plane, or control plane, which represents the space of all iso-surfaces. The system can color points of the control plane with information computed for corresponding iso-surfaces. As the user navigates the data by small changes in time or iso-value, the system can exploit coherence to update the iso-surface at the client. We have begun to explore several issues and tradeoffs for such a system: from data structures and algorithms to modes of user interaction. In this abstract, we report on initial feasibility studies for displaying topological properties of iso-surfaces at corresponding points of the control plane. We begin by describing the splitting of dimensions between iso-surface and