ISTV: Interactive Structured Time-varying Visualizer

The Interactive Structured Time-varying Visualizer (ISTV) visualization system, written at the NSF Engineering Research Center for Computation Field Simulation, Mississippi State University, was originally designed for high-performance interactive visualization of very large oceanographic models. However, its design is general enough for other scientific visualization work, and it has been used with structured datasets from a variety of domains including computational fluid dynamics, electromagnetic simulations and medical imaging. ISTV is written in C using OpenGL for graphics and X/Motif for the user interface. Initially written for SGI IRIX workstations, ISTV has also been ported to Sun Ultra workstations with OpenGL hardware support. During the past two years, computational grid resolutions in global models the authors routinely work with have increased by a factor of 16; their visualization products have adapted to this explosive growth by adopting more efficient data access techniques while retaining the ability to work with model output in its native format. ISTV's data model and distributed visualization capabilities are discussed below; the distributed visualization capabilities include a data server using the message-passing interface (MPI) to communicate with the visualization front-end, providing improved access to data using both multiprocessor machines and networks of heterogeneous machines. The simultaneous visualization of several datasets with varying temporal and spatial resolutions in a single view volume is also supported by ISTV; case studies are presented demonstrating this capability. Effective analysis of ocean flow requires the identification of vortical structures; ISTV provides a visualization technique using a two-dimensional mapping with a hue-saturation-value color wheel, giving researchers insight into ocean eddy structures while avoiding the display clutter associated with conventional vector field visualization techniques.