Is a VRML style 3D interface likely to improve any day to day productivity applications? Aren't there cases where 3D metaphors confuse more than they clarify? If so, will future users feel comfortable hopping back and forth between 2D and 3D environments over the course of an average workday? Are DOOM and Quake the killer apps of the 3D interface, or is there something more enriching lurking around the corner?

Most new technologies start out declared as the answer to every problem. Then, people find out what pieces of the world's problem they actually solve and they quietly take their place among the other solutions. For example, microwave ovens were heralded as replacements for every appliance in your kitchen.

Instead, microwave ovens became yet another tool in the kitchen. Microwave ovens became indispensable as a minor adjunct to primary cooking processes taking place somewhere else.

Similarly, 3D, along with handwriting, gesture, and voice recognition, will take its place as one technology among many, there to perform whatever large or small measure of an overall activity may be needed.

An area of 3D that has not yet been fully appreciated is the illusion of depth that can be generated on a normal, 2D screen. Xerox PARC has a cone tree allowing rapid document retrieval. MIT Media Lab has interesting infinite spaces within a finite boundary 3D worlds for document retrieval.

3D on screens will not work well until we drastically improve resolution. Sun Microsystems has built a 3D camera that can feed onto a 2D screen. Users wearing shutter glasses would then see a 3D image that would move vantage point as the user moved in space before the screen.

The only way we can achieve enough depth on our display to enable users to explore the depths of a 3D image, with or without shutter glasses, is to drastically increase the resolution of our screens. 300 dpi is a start. 2400 to 4800 is what is needed.

Which brings us to VRML, it doesn't work, and it won't work until the resolution is drastically improved. Sun Microsystems has built a VR room with three high resolution projectors throwing millions of pixels on three screens that wrap around you. The resolution is close to approaching adequate. The resolution in head mounted displays is very poor, and it will be for a long time to come.

People flipping back and forth between 2D and 3D graphic designs on 2D screens will occur not over the course of an average working day, but over the course of an average working minute. People will also adopt and adapt to simple hand held 3D devices, even if they must wear light weight shutter glasses to use them. People will not walk around the office wearing head mounted displays. Mainstream VRML is a long way away.

When does 3D fail us? When it's misused to represent documents. It's understandable that we'd first want to use 3D as a front end to our document spaces, after all, document spaces are the bedrock of the 2D GUI's. But try reading a textual document in a 3D space, it's almost impossible. You need to face it head on, get close enough, and probably pitch your head up and down to get all the text. That is the misuse of a powerful tool, trying to adapt it backward into a preexisting paradigm, rather than jumping forward into a new one.

On the other hand, if you're trying to understand the relations between a set of documents, considering such metadata as age, size, creator, geographical region of interest, language, specific subject being covered you can see that very soon we'd exhaust the limits of representability within a 2D GUI, and would have to resort to some pretty fancy tricks used by both the Windows 95 and Macintosh desktops to tame this chaotic sea of metadata complexity. Already the desktop metaphor is breaking down, precisely because it was designed around a document centric view of the world.

But the World Wide Web isn't just a swirling sea of documents. It's an active space which conforms itself to requests made of it, a far cry from a database of documents.

The Internet is not a plug in. And the desktop is not reaching out to the Internet, rather, the Internet is reaching out to the desktop. But the desktop can't cope with the scope of this transformation, furthermore it's unrealistic to think that it should. In fact the Internet confronts us with a riot of information, and right now 3D interfaces are the best hope for interfaces which can "tame" the information overload.

It is necessary to realise that the navigation of VRML worlds is moving us in a direction, based on a need for different points of view of solid spaces and objects. It seems that from the cognitive research, people use the extra z axis, forward and back, for remembering where objects are placed around their work surfaces, as well as in x laterally and for a limited range of y. As we walk around our office environments we use the z dimension to move into additional spaces, but there is little relative change in our y axis knowledge (height). What is critical is to limit the users options somehow to avoid additional axes of control confusion, encountered in real flight from six degrees of control. We still need to do some quality perceptual cognitive research in this domain. The ability to provide true 3-D or stereo perspectives is still computationally and hardware limiting.

We will also see more interfaces use concepts such as layering or overlapping transparency, which has been termed 2.5 D, as seen in MITs spatial data based management system in the 70s. Current work at the Media Lab in the Visual Language workshop has started to show great promise in applications of transparency and focus pull for navigating libraries of data sets. The smoothness and speed of response of these systems shows the hope for systems such as VRML, when we have more computational power available on set top boxes. Clearly the use of 3D is much clearer when we know there is some inherent 3Dness to the data. Exploring geographical data is much easier given the known 3D world metaphor, moving over body data is made clear when using a real 3D body, and then there is the presentation of 3-n D data across time. Animation is a useful tool to show data relationships, but additional axis of display representation can facilitate the understanding of their interrelationships too. It depends on the types of data being displayed, and the users task as to whether additional axes show any real benefit in performance or learning.

Applications that make the best use of 3D need more time to develop. At the moment there is very limited special purpose uses only for 3D. Sometimes designers use 3D either for feature appeal, or as an excuse for poor design when they cannot think of a 2D solution. With a new generation of game playing kids, the controls over 3D spaces will possibly be needed to keep interest high in work applications. The limitation of the flat existing metaphors is somewhat constrained by the current I/O devices. The pervasiveness of the keyboard will be limited to work processing activities, and will change when we think of a computer as being more than a heavy box shaped screen that we sit at everyday. The keyboard does not have a place in the living room, which will make it take alternate form factors along with the navigational control over n dimensional custom spaces.

Manipulation of 3D spaces and 3D objects isn't easy with just a mouse and keyboard, and will need new hardware inputs to become commonplace before people can effortlessly control themselves and objects in 3D spaces.