Internet Archaeology 10 - Jeffrey. Intro,

1.0 Introduction

This report describes work in progress on my Ph.D. thesis, which is part of the Scottish Early Medieval Sculptured Stones (SEMSS) project based at the University of Glasgow. The project has many objectives relating to the recording, conservation and enhanced understanding of Scotland's large collection of sculptured stones (Campbell 1998). One of the core objectives is to present more and better information on all aspects of this resource to both the academic community and the general public. As a means of doing this, the Internet immediately presents itself as potential solution to the problem of disseminating large amounts of information in varied formats to the largest possible audience. It is envisioned that the SEMSS project will generate a large amount of information, including three-dimensional models of selected sculptured stones. Three-dimensional models are seen as an important way of enhancing our understanding of how these artefacts were meant to be perceived. The overall impression of free standing monuments, lines of approach to them, the relationship of one sculptured panel to another and how the monuments relate to the landscape can all be better understood using 3D representations. There are many ways in which these three-dimensional models could be presented to their target audience, each with its own benefits and constraints. In the case of the SEMSS project there are a number of requirements that make the presentation format challenging to select. The six main requirements can be summarised as follows:

1 The object modelled (sculpted stone or fragment) should be shown in relationship to its original environment, where known. A very large number of these stones are not in their original context, having been moved for a variety of reasons. This means that presenting the stones in a representation of their original context may involve visual reconstruction of that environment. For example if the original context was rural, but is now built up, a representation of the original rural context would have to be generated.

2 The relationship of wholly reconstructed segments of the model to actual recorded segments must be clear to the viewer. Many of the sculpted stones are either damaged or fragmentary. A recording technique will generate a model of the stone as it currently exists, and this model will provide a base for the joining together of fragments or the reconstruction of missing segments. Because there is a significant difference between the level of interpretation in the recorded segments of the model and the reconstructed segments of the model, there should be a clear visual indicator of how each segment was generated. Traditional archaeological illustration and reconstruction of, for example, ceramics and frescoes already have conventions to distinguish between 'recorded' and 'reconstructed' segments of artefacts. The potential realism of computer-generated models makes the need for similar distinctions and conventions even more vital; an internet discussion group, Visualisation Standards in Archaeology (VISTA) exists to promote the formulation of these conventions

3 The three-dimensional integrity of the model must be maintained. This means all surfaces that were ordinarily meant to be seen and appreciated in the past by the early medieval audience must be available to the modern viewer. This requirement actually has the effect of allowing for a presentation format that does not, for example, allow the viewer to see the very top surface of a six-metre high sculpted stone, as it would not ordinarily have been seen in the past. However, three-dimensional relationships between areas of sculpture on a monument and their relationship to the complete monument mean that the whole monument should be seen as greater than the sum of its parts. In order for this to be achieved, the modern viewer must be able interactively to examine the whole monument as a three-dimensional object rather than as a series of detailed segments.

4 The user should be able to examine the model at differing levels of detail. Many of the stones are highly detailed as well as large. The viewer should be able to appreciate the overall size and shape of monument as well as being able to study details on its surface. This means that the minimum acceptable level of interactivity would be the ability to zoom in and out of the model and rotate it horizontally.

5 The user should have the ability to alter the lighting direction. The angle of lighting is often crucial to a clear 'reading' of surfaces carved in, or surviving in, low relief. In order to form an interpretation of the surface, it would be desirable for the user to be able to change the angle of lighting interactively in order to bring out detail.

6 The model must be available in at least one presentation format that is reasonably suited to distribution over the Internet. This means that considerations such as file size and the need for plug-ins or helper applications are important.