Open GL Super Bible

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Open Inventor and VRML

To understand the relationship between Open Inventor and VRML, you may want a little more background on Open Inventor. This object-oriented library and tool set is implemented using OpenGL. The programming library is almost always used from C++, but C bindings exist, as well. This object-oriented approach provides a much higher level of control over the objects and scenes being composed.

When OpenGL is used to create a scene or object, each function and command has an immediate effect on the frame buffer. Unless you are using double buffering, the results of each action are immediately visible on screen. This is known as immediate mode rendering.

Open Inventor, on the other hand, operates in what is sometimes called a retained mode. In this mode you use various commands and functions to compose a scene database. This database of objects and materials is then rendered all at once to create the scene. The real power of retained mode is that individual objects in the scene can be manipulated very easily programmatically. Furthermore, relationships between objects can be established that allow the manipulation of one object to affect other objects (such as linked assemblages or mechanical models). Object engines can also be used within the database to perform rotations, animations, and other actions. This information is then embedded within the scene description, and no further programming is necessary on the part of the developer.

The VRML 1.0 specification is based entirely on the Open Inventor 3D file interchange format. This file format, which is nothing more than the scene database in a standardized layout, allows 3D graphics designers to easily exchange objects and scenes when using Open Inventor-based tools. It’s easy to store a single object or an entire scene filled with objects, in a single file.

Summary

WebSpace is not the only way to visit cyberspace in 3D. Many other vendors (including Microsoft) have hopped on the bandwagon and developed their own VRML viewers.. WebSpace does offer the unique advantage of compatibility with nearly any Web browser and will load and view both VRML and Open Inventor files, either uncompressed or compressed.

Even as this chapter went to production, the battle was raging over who will set the standards for VRML version 2.0. These newer versions will add new features for animation and multimedia enhancements to 3D scenes viewed over the Internet.

Is virtual reality over the Internet just a passing fad or the beginning of a revolution? Only time will tell, but there is a universal law at play here: “Demand will always consume available bandwidth,” whether it’s processing power, communication speed, or graphics capabilities. As computer networks manage more speed and work with better graphics hardware, you can be reasonably certain that virtual reality is here to stay. It is only going to get faster, more realistic, and more capable of simulating the world in which we live.


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