The network illustrating the use of the AVS 5 `hedgehog` module is contained
in the file `~kpulo/ass2a.net`, and is shown in Figure 1.

The `hedgehog` module accepts three main inputs -- the 3D vector field
to visualise and a corresponding 3D scalar field and colourmap, with which to
colour the vectors. The colours are generated from the magnitude of the vectors,
with the colour range (a standard AVS colour ramp) being applied between the
minimum and maximum values of the vector magnitudes (this is the function of
the `minmax` and `color range` modules).

The `tube` module converts lines, that is, the vectors and their arrowheads,
into 8 sided cylinders. This makes the visualisation slightly slower (and this
impedes interactivity slighly), but gives the vectors a much more ``solid''
look, as would be desired when outputting to video or giving a presentation.

The `hedgehog` module also provides interactivity, where the plane of
vectors to be visualised can be manipulated in the `geometry viewer`
window. This allows the user to examine the data set by moving the plane around
in the data cube.

2000-08-22