Internet Archaeol 1. Gillings & Goodrick. 2.4.4

2.4.4 The need for Modelling Programs

Although the structure of VRML files is relatively simple, several factors serve to complicate the production of files based upon archaeological data.

Each triangle in a triangulated irregular network (TIN) or face in a 3-D AutoCad file requires many lines of ASCII code. The files can therefore soon run into several thousand of lines of information. Even with the use of extensive remarks, navigation within the files can be very difficult.
Maintaining a mental picture of the current local co-ordinate system relative to the previous system is impossible in all but the simplest of scenes.
Debugging tools, as used in conventional programming languages, are neither currently available nor appropriate for VRML. VRML is very syntax sensitive and errors that may not produce obvious effects may result in errors throughout the rest of the file. These errors can be as simple as the presence of a single character in the wrong case, yet can seriously compromise the accuracy of the resultant model.

The simple structure of VRML does, however, make the production of macro-language routines for the export of models from host formats to VRML relatively straightforward. Routines are already available for packages such as Autodesk's 3-D Studio, and the current home-grown Arc/Info conversion utilities are due to be replaced by integral tools in the next version release of this industry standard GIS package (pers. comm. Paul Miller). Perhaps most useful for archaeology are the existing tools for the conversion of the popular AutoCad data exchange format (DXF) into VRML, making the conversion of existing 3-dimensional CAD drawings relatively straightforward.

For most scenes these conversion routines are adequate, but in the normal process of constructing an archaeological model other capabilities are required. VRML modelling programs offer the ability to build scenes from scratch or construct and enhance scenes using pre-defined components. They also enable the builder to incorporate bitmap images to use as textures, for example satellite images, rectified building photographs or fractal generated overlays using landscape visualisation packages such as Vistapro. All of these result in a much greater sense of realism in the scene. By using modelling programs you also gain the ability to fine-tune scenes; surfaces may be smoothed, component polygon counts reduced for greater speed of rendering, and cameras can be added to provide default views. The most popular modelling package in current use is Caligari Pioneer.

It should be noted that VRML is very much in the early stages of its development and standards are still open to very different interpretations. Different VRML browsers and modelling programs may use quite different interpretations of the VRML standards to implement very different features. Despite the presence then of complex modelling programs to assist in the production of VRML documents, it is still necessary to be able to understand the basic syntax and to be able to code 'by-hand' to be able to tweak files to satisfy different browsers and to use capabilities added to the VRML specification after the modelling program was written. Hopefully this requirement will diminish as the technology matures.

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