Jean-Luc Movie: /NCSA1999/BlackHoles/bs_384_0.2/Psi4AH

Psi4AH

While Psi4XZSlice shows only one 2D slice in the xz plane, this animation shows various intensity levels of the \Psi_4 field as thin transparent surfaces, nested like the skins of an onion. This highest intensity level is rendered white, while the lowest intensity level (some small value larger than zero) is rendered dark red.

Such an image can be achieved using a couple of isosurfaces. Actually, this animation sequence does not compute isosurfaces but uses `volume rendering' with a special colormap, such that most data values are rendered transparent, but some specific ones are semi-opaque. This reveiles a more realistic appearance for the transparent surface levels and rendering is much faster with poweful hardware graphics than rendering a comparable number of isosurfaces. In this context, the technique of using volume rendering for isosurface-like computation is called `volumetric isolevels'.

In addition to the volumetric isolevels, the data is enclosed in a five-sided bounding box. When the gravitational waves touches the bounding box, the walls becom `glowing' at the regions of high \Psi_4 intensity level. So the bounding box walls serve as five 2D slices at the data boundaries. It enables one to see the cross sections of the gravitational waves in addition to the 3D structure. E.g. note the `dipole-like' structures occuring at the +z and -z walls, when the gravitational wave leaves the box. Such structures are invisible when looking at the 3D data alone.