Fast time-dependent isosurface extraction and rendering.

For the visualisation of time-dependent data sets, interactive isosurface extraction and rendering is desirable. It allows the user to study the development of a surface shape in time, such as a moving front or an evolving object shape. For this purpose, the user must be able to interactively specify an isovalue, and a sequence of isosurfaces must be visualised, starting from any time step, in forward or backward direction in time. In this paper, we describe efficient and tightly coupled techniques for time-dependent isosurface extraction and rendering at interactive frame rates. In preprocessing, we create data structures from a time-dependent data set that allow real-time extraction of all isovalue-spanning cells, achieving rates of several hundreds of frames per second. These isovalued cells are then passed to a fast hardware-assisted direct point rendering algorithm for display, thus avoiding time expensive surface construction by triangulation. This algorithm makes effective use of the available graphics hardware.