The first of these is iso-surface. It's akin to contouring of an image extended to three dimensions. Each coloured surface corresponds to a constant data value. In order to see inside a surface, each surface should have an opacity that is less than 1.0. An example using the same Orion dataset is in the figure below.
Figure: Isophotal
contours with various colours and opacities allows you to see different depths.
Just as with the contouring in GAIA, there are different methods to generate iso-surface levels authomatically, as well as manually.
You can adjust the viewing angle and zoom factor either with the mouse, or with the keyboard for finer control. The online help lists the various controls. There are many options to control the appearance, such as directional and annotated axes. GAIA can also display the current slice and displayed spectrum. It is also possible to display two cubes simultaneously, say to compare data from different wavelengths measuring different molecular species. GAIA provides a number of alignment options in this regard.
The second function is volume rendering. It displays all the data within two data limits as a single volume. You assign a colour and opacity to each limit. The controls and options are the same as for the iso-surfaces. See the figure below.
Figure: Volume
rendering of the Orion dataset. The colour transfer function is a
simple mapping between two selected colours between a supplied data
range.
These visualisation functions place heavy demands on computer memory and CPU. Also a modern graphics card with hardware support for OpenGL makes a huge difference in interactive performance. So you will need a modern machine to get the best out of these tools. Of the two tools, iso-surface is quicker to render and uses less memory.
The IFU Data-Product Cookbook