Red and magenta depict regions of large angular velocity on the surface of the vortex tube, while flow in blue and green areas has lower angular velocity. The grooved indentations follow the path of streamlines on the tube's surface, providing a sense of the vortical motion. Graphic courtesy of Thomas W. Crockett. With this approach, a parallel software renderer is coupled directly to the application code, replacing the hardware rendering engine found in graphics workstations. Because the supercomputer is performing most of the graphics work, inexpensive desktop workstations have sufficient power to decompress and display the images.
Images are often much more compact than the simulation data from which they are derived.
The use of compression, color reduction, and lower-resolution images can often reduce the image data to a size that can be transmitted satisfactorily over local area networks at rates of several frames per second. For slower long-haul links, more aggressive lossy compression techniques can be employed to maintain adequate frame rates, with higher quality images being stored on the supercomputer's disk for later viewing. Interactivity can be provided by means of a graphical user interface that runs on the user's workstation and sends rendering and visualization commands back to the parallel application. This allows the user to monitor the progress of a simulation, modify viewing and visualization parameters to explore the dataset, and potentially adjust critical parameters or terminate the job if it is not producing the desired results. In order for this approach to be successful, efficient parallel algorithms are needed to perform the graphics and visualization operations.