Martin Doody, director of the Ballyhoura Hills research project first approached the department with the aim of reconstructing a series of Bronze age houses uncovered by excavation at Chancellorsland, Co. Tipperary in 1992.
The hardcopy excavation plan must first be converted into a compatible digital format for use the base drawing or 'floorplan' in AutoCAD. Digitising and scanning are both suitable (scanning being the less laborious method). It is necessary for the archaeologist to have a design 'blueprint' for the structure based on the available evidence, prior to any modelling taking place. One interesting point, and perhaps one of the main advantages of recreating a structure using this process is that almost as an architect designs a building today, the initial design can change as it is being created in 3 dimensions on screen, as the software allows us to see that some interpretations of the evidence would be physically impossible or at least very difficult to construct in the field.
With a final design decided upon, the drawing process can begin. The basic solid modelling features within AutoCAD are adequate to create most structural components in the model. These tools are easy to use and help to keep the overall size of the drawing down. What remains after the drawing process within AutoCAD is complete, is a rather complicated looking 'wireframe' model with hundreds of tessellation lines. This wireframe model offers the viewer little information as to the physical appearance of what the structure may have actually looked like. In order to create a more realistic image, the model must undergo a process known as rendering.
In simple terms, rendering involves 'painting' the components of the wireframe model with textures representing any materials, which would have been used to build such a structure. AutoCAD comes with a materials library containing a limited amount of textures, although new materials can easily be created by scanning and cropping photographs. The texture images must be then mapped onto the components of the drawing. In AutoCAD there are a number of options for projecting bitmaps onto objects. These include planar, cylindrical, and spherical projections. It is also possible to define a co-ordinate sytem for the image being mapped. Users should experiment with the different options available, as this is an integral part of obtaining realistic effects in a model. Textures can then be configured to represent the materials' roughness and light reflecting properties.
In addition to textural information to the drawing or 'scene', data regarding geographic location and time of year can be input in order to produce realistic lighting and shadow effects. When all the relevant options have been configured, the model is rendered. This can be quite a time consuming process depending on the level and nature of detail in the scene, and the speed of the hardware being used. Some examples of rendered images of the Chancellorsland structures can be seen below. As can be seen from some of the thumbnails shown, the results that can be achieved are very effective.
The advantages of this form of site reconstruction are vast and it is not intended to discuss them in any great detail here. Computer reconstructions can greatly aid in the archaeological interpretation of a site. One of the main advantages is that the computer reconstruction can provoke the archaeologist into considering various hypotheses regarding the nature, use and construction of a site by immersing himself/herself into the virtual representation and being able to navigate feely around the model.
The 3D reconstruction can never be considered to be completed. The nature of such models enables new archaeological evidence pertaining to a particular structure, or advances in software to be encompassed into the model with ease. The importance of the 'virtual site' also has immense implications for archaeology which is in danger of disappearing due to environmental factors. Not only does the virtual site form a permanent digital record, but the combination of VRML (Virtual Reality Modelling Language) and the internet allows for an infinite number of people to 'visit' the site from around the world via the use of freely available vrml browsers, hence eliminating any of the hazards associated with physical contact to the site. The combination of computer aided site reconstruction with GIS based regional analysis provides for a very powerful research tool.