Terminology

VirtualUniverse

A VirtualUniverse object defines a named universe. Java 3D permits the creation of more than one universe, though the vast majority of applications will use just one. The VirtualUniverse object provides a grounding for scene graphs. All Java 3D scene graphs must connect to a VirtualUniverse object to be displayed.

 

JAVA 3D's superstructure consists of one or more VirtualUniverse objects, each of which contains a set of one or more high-resolution Locale objects. The Locale objects, in turn, contain collections of subgraphs that comprise the scene graph

The Virtual Universe

Java 3D defines the concept of a virtual universe as a three-dimensional space with an associated set of objects. Virtual universes serve as the largest unit of aggregate representation, and can also be thought of as databases. Virtual universes can be very large, both in physical space units and in content. Indeed, in most cases a single virtual universe will serve an application's entire needs.
Virtual universes are separate entities in that no node object may exist in more than one virtual universe at any one time. Likewise, the objects in one virtual universe are not visible in, nor do they interact with objects in, any other virtual universe.
To support large virtual universes, Java 3D introduces the concept of Locales that have high-resolution coordinates as an origin. Think of high-resolution coordinates as "tie-downs" that precisely anchor the locations of objects specified using less precise floating-point coordinates that are within the range of influence of the high-resolution coordinates.
A Locale, with its associated high-resolution coordinates, serves as the next level of representation down from a virtual universe. All virtual universes contain one or more high-resolution-coordinate Locales, and all other objects are attached to a Locale. High-resolution coordinates act as an upper-level translation-only transform node. For example, the coordinates of all objects that are attached to a particular Locale are all relative to the location of that Locale's high-resolution coordinates.


The Virtual Universe


While a virtual universe is similar to the traditional computer graphics concept of a scene graph, a given virtual universe can become so large that it is often better to think of a scene graph as the descendant of a high-resolution-coordinate Locale.