What Is a VRML File

VRML acts in many ways, the same way HTML files can produce many different effects on the screen. A VRML file is composed of a series of text commands that are interpreted by the VRML browser and displayed on the screen, but the file's objects are all three-dimensional. This content is referred to as a world or scene. In HTML, you place text and images on the screen using tags. Similar to tags, VRML files have nodes that define 3D objects such as cubes, spheres, and other shapes in a real 3D coordinate system. With the browser, you can navigate around these worlds at your own pleasure, examining the world from whatever angle you want. Basic worlds can be enhanced by adding lights, colors, textures, and motion to the scene. To navigate around the scene, you move the mouse-the scene changes in real-time. So, by moving the mouse forward, the objects in the world become larger, as if you're approaching them. If you pull the mouse back, the scene recedes. If you click and drag the right mouse button, the entire scene rotates around its center. How VRML Is Similar to HTML Just as HTML is designed purely for document formatting, VRML is designed for 3D VR scenes. Most of the rules of creating Web pages also apply to creating 3D worlds. If you create a 3D scene, make sure it's interesting and offers the user something to do. Similarly, if you create a plain HTML page with no headings-just pure text-it too will be boring, ensuring that visitors don't return. Say you create a Web page that looks absolutely stunning with lots of graphics, but it takes twenty minutes to download-how often do you expect people to visit? You must apply the same rules to creating VRML worlds that you do to creating Web pages. By its nature, VRML creates larger files than HTML does, but you can keep the file sizes to a reasonable level. Limiting the use of large images (textures), sticking to using color only, and using simple primitives are some techniques "Tricks to Optimize Your VRML Worlds for the Web," covers some of the common methods for optimizing your creations to keep people coming back. An outstanding Web page can be put together in a couple of hours, if you have all your resources ready to go. Because VRML is more complex, it takes more time, even when you're using a GUI construction tool. However, it always pays to spend some time planning what your new world will look like in all three dimensions. Once you add in that third dimension, VRML starts to diverge from its 2D "relation." HTML pages can be viewed in only one way, defined by the page writer, but users can explore VR worlds by looking at them in whatever way they like. The similarities between the two technologies stretch further than just the method of creating them. Many HTML pages are designed much as magazine pages are, with lots of pretty graphics and links, and some cutting-edge pages seek to break this mold by stretching technology to do something unique. VRML is no different. A vast majority of VR worlds use traditional earthbound paradigms, such as the shop and art gallery examples presented in this book. However, a few stretch the limits as they seek to explore the possibilites of virtual reality. VRML offers a whole system for artists to create with, but HTML only allows them to display one of their creations. When creating a Web page, you can do it in several ways. You could use a plug-in to common word processing packages (Internet Assistant for MS Word), a standalone application (Sausage Software's Hotdog or MS FrontPage), or the text editor of your choice. Equivalents exist for VRML world builders. You can export files from packages like AutoCAD and 3D Studio, use standalone dedicated applications like VRealm Builder, or use a text editor. However, with the pace at which VRML is developing, you should get familiar with a text editor. The best worlds are still created by hand, particularly when it comes to creating behaviors in VRML 2.0. Working in Three Dimensions One of the most important differences between VRML and HTML is that with VRML you have a whole extra dimension to worry about. This added dimension gives the visitor to your VRML world the chance to go inside, behind, and around your scene. This can be used to your advantage, but it also presents some difficulties. The next section examines some of the advantages and disadvantages to working with this third dimension. Advantages First, you have more freedom. All those 3D effects you've been producing in earlier sections of this book can now be done in real-time. Instead of just looking at a picture of a car, you can walk around it, kicking virtual tires if you like. The images and animations created up until now are all canned. You can play the animation a thousand times and it always looks the same. A VRML world, on the other hand, presents infinite ways to view the animation, all at the viewer's discretion. VRML has a second advantage: control. Users can view the scene from any angle (if they can effectively navigate), so they aren't stuck viewing the same image every time. A third advantage to VRML is the ability to obscure items. By using the third dimension, you can hide items behind other items, something tricky to do on HTML pages. This enables you play some interesting hide-and-seek games. Perhaps the greatest advantage to using the third dimension is the realism you achieve. Moving a user through an architectural structure gives them a much better feeling of spatial relationships for the building than pictures do. One of the intended uses of VRML is in the remote visualization of data. This might take the form of a VR world that mimics the environment a remote-controlled vehicle is operating in, or it might even act as mock-ups of designs. Now, there are several other languages and file formats that could do this, but VRML was born with the Internet firmly in mind. Anyone should be able to view any VRML world without needing proprietary software. VRML has the same benefits for users in the 3D arena that HTML has for people working in 2D environments and document publishing. Disadvantages Probably the most challenging aspect of working in 3D is trying to manipulate a 3D model in 2D. Input devices like the mouse are two-dimensional, so moving them in 3D can be difficult. Even with 3D-based interfaces like Caligari's Pioneer, or the split view approach of 3D Studio, it's still difficult to keep track of exactly how things look until you get to see them in the final environment. Not only are computer input devices 2D, so are output devices, such as the monitor. Moving around the world helps the viewer understand the relative positions of objects, but it's still difficult to determine depth on 2D monitors. In the future, head-mounted displays will help. Head-mounted displays are worn like glasses; the scene changes as you move your head. To see the object behind you, you turn around. The main disadvantage to working with real-time 3D is the computing time involved. The poor little processor really has to work hard to calculate how the scene looks as you move. The more complex the scene, the more it taxes the processor. Because of the huge calculations involved, the details of VRML worlds are purposely kept simple. You may have noticed that the images in the first half of the book don't really compare with images created in a VRML world.The scenes in the first half are drawn only once, but in VRML, the world may be redrawn as often as 30 times a second. Complex scenes take longer to draw, so to keep users happy, the world is much less detailed. Complex pre-rendered animation can take all night to produce just a single frame of the animation, but when the animation's complete, you can play it as fast as you want. VRML worlds have less than a second to compute and render the scene before your eyes detect that the motion isn't fluid. So until processors get much more powerful, you're stuck with the simple-looking worlds. ...

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