At predetermined intervals of time during the CFD simulation, our mpf program would recognize that a volume-rendered image of the flow should be constructed for inclusion in an animation sequence. At each of these instants in time, data was transferred from the MasPar CFD application to the Sparcstation rendering tool by simply writing one 3D data array (of cloud densities) to an NFS cross-mounted disk. Process control for the visualization task was then passed from the MasPar to the Sparcstation via unix sockets. After spawning the visualization task, the MasPar would continue following the evolution of the fluid flow, running the CFD simulation task in parallel with the visualization task on the Sparcstation. As the volume-rendering algorithm finished generating each image, it would immediately delete the 3D density data array, thereby conserving substantial disk space.

One example animation sequence that was created in this manner is presented in the above animated gif. The animation shows the evolution of a stable, common-envelope binary star system that was studied recently by New and Tohline.¹¹

At both supercomputing centers, these two selected hardware platforms have not been installed with the idea that they would provide an HCE for the general user. Indeed, at neither center do the platforms even share cross-mounted disks. Hence, we have had to rely upon ftp commands to transfer data from the Cray T3E to a disk that is mounted on the SGI Onyx, and process control for the visualization task has been passed via a remote shell script. Figure 2 illustrates schematically how the link between the Cray T3E and the SGI platforms is initiated on the Cray T3E, and Figure 2b shows illustrates how the link is completed on the SGI Onyx.

Figure 2a

Figure 2b