The structure is used to create a system where the scientist can select how much detail he wants to see at a given time. There is a trade-off. If we show many things, the visualization is not interactive. So, you may want a low-resolution image to navigate through your data set, and when you find something interesting, you switch to high resolution. We use this system to generate isosurfaces and to ray trace for volume rendering.
Most scientists use Fortran for their simulation code.
This is a jet simulation in which the scientist is inside the jet plume. The colors on top of the surface are the values of the pressure. In this case, scientists are looking to improve the performance of jet engines in planes and missiles. They run the simulation and change several parameters to see how the choice of parameters affects the simulation. They look for the right shape of the structures described above.