There are three main sources of information that you can draw on to learn more about how to use Open Inventor:
Toolchestmenu that should be showing on your desktop when logged into an Athena SGI. The
Helpmenu option will lead you to the collection of online books. This book is also printed in a softcover format by Addison Wesley.
man(online manual) pages for these classes, with the same name but usually beginning with the letters "So". For example, to find out more about
Conenodes, you could just use the command
"man SoCone"from the Athena prompt.