Vol. IX, No. 4

February, 1997

Almost Virtual Reality

Harrison Eiteljorg, II

Rendering of older propylon on the Athenian Acropolis, a screen image captured from the program WalkThrough.

I walked through the older propylon on the Athenian Acropolis one day recently - the reconstructed version from about 460 B.C. I did not have to fly to Athens to do it; of course, the reconstruction is not on display there anyway. I just opened the computer model I had made with a new program called Autodesk WalkThrough® and found myself facing the Acropolis and ready to walk through the site. I moved through a rendering of the propylon by moving the computer's mouse - "walking" forward or back, right or left. From any position I could look around, turning clockwise or counter-clockwise, up or down. I could move slowly or quickly, as I chose. The quality of the rendering was a bit rough in places (partly because of the nature of the model), but it was very impressive to move around the reconstructed version of the older propylon - a structure on which I have worked for so long. It was especially exciting to move into the middle of the upper courtyard and look around at it, consider how large the gate opening seemed, think again about the problems created by the positions of the steps there - but this time while seeming to look at those steps from within the courtyard.

I was also struck by how obvious the importance of the Mycenaean fortification wall became. The cramped space where the remains of the older propylon lie and the partial state of preservation of the wall make it difficult to appreciate its importance to the old entrance design. Seeing the area with this program and realizing how much the wall dominated the entrance, I understood at once how important the wall was to the nature of the design.

Such was my first experience with WalkThrough. I learned about this relatively inexpensive ($250) product, by accident, from the Autodesk Web site just a few days after its release. It runs on a PC (at least a Pentium running Windows 95 or Windows NT), and I think it is a promise of marvelous things to come.

WalkThrough provides only a portion of the power of the high-end simulation system discussed above ("The Rome Reborn Project,"), but, though I've only had a few days to work with it, I am enthused. This program allows me to walk through structures with the aid of my PC, not a special-purpose, high-end machine. Furthermore, it works with DWG files, the AutoCAD® standard (about which, see the following article). All our CAD models are DWG files; so I need not do anything to them before using them in this program. (1) (The program can also use files in the DXF - drawing exchange - format.)

WalkThrough is not in the same league, in features or cost, as the uSim program used at UCLA, but, if the history of CAD software is a guide, it will get better very quickly. One can expect low cost virtual reality software on standard PC hardware to close the performance gap quickly, if not completely.

The program opens a model file as it was last stored - with layers visible according to their condition when the file was last saved and with the point of view as in the file when it was last saved. Colors of surfaces are also determined by the colors in the model; textures are added in WalkThrough - either to individual drawing entities or to layers. I am still learning how to use the textures effectively, but the many possible adjustments have made it possible for me to produce very acceptable surface textures with no training (or printed manual!).

I could manipulate the lights - of which there could be many - only with some difficulty. With patience, very good lighting effects can be created.

Changing the display of layers is not easy. A list of layers is available, and each layer may be turned on or off individually. Since our layer naming scheme is built around AutoCAD's ability to select any number of layers with complex searches, however, I would like to have the flexibility of those searches here as well. Indeed, given the large number of layers used in the model, it was simpler to run AutoCAD while running WalkThrough. Then I could change the active layers in the model in AutoCAD, re-save the model, and re-open it in WalkThrough. That was quicker and easier than dealing with many layers in WalkThrough directly.

The program is relatively slow on our Pentium laptop, making me wish for some tools to by-pass intermediate steps. On the Pentium Pro desktop machine, though, the program runs more quickly and smoothly.

There is no output format for printing or saving individual images, but animations can be saved. The image produced here was made from a screen-saver utility; so it is not of the quality of the image on a good monitor. Of course, the screen image was in color as well. The point of the program, however, is the walk-through, not a rendering. The quality of renderings produced by 3D Studio (discussed in the last issue of the Newsletter, "Visualizing the Ancient World") or other good rendering programs should be much better, though those programs require file format conversion and new renderings when the underlying model is changed.

My few complaints are minor compared to the joy of using a virtual reality program that seems relatively intuitive to use, runs on PCs, accepts standard AutoCAD models with no modification, and has a modest price tag. I am hooked.

For other Newsletter articles concerning the use of CAD in archaeology and architectural history, consult the subject index.

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(1)The advantages of working with a DWG file are enormous. Not only is it possible to view a model without alteration, but both AutoCAD and WalkThrough are using the same file. Therefore, any changes made to that file are immediately apparent in both AutoCAD and WalkThrough views of the file. Return to body of text.