Organizing the Scene Graph Through BranchGroups
To repeat, in Listing 11.1 we instantiate two separate BranchGroup objects and add them to the Locale object; one to represent the content subgraph and the other to represent the view subgraph. You are urged to get used to this structure because it is always present.
In the vast majority of cases, there is only one Locale. (Occasionally, there are more than one.) In all cases, there is one and only one VirtualUniverse. Thus, “the trunk of the tree” of a Java 3D scene graph is fundamentally the same for every program.
From this discussion, you can see that the top operating level for the developer is at the BranchGroup level. You will be well served in understanding and thinking of the Java 3D program ...