Realistic Graphics in Archaeology?
“Currently, many virtual reconstructions are limited because their level of realism cannot be validated. The generated images may look realistic, but their accuracy is not guaranteed since they have no physical basis in reality.” (Devlin et al 2001)
There is great potential, but also incredible danger in incorporating three dimensional technologies into the study of archaeological sites. In particular this is most poignant in areas where reconstructions factor as both a base for visualisation and as an analysis for artifacts and structures that are no longer present. Constructing imagery using the latest programs and techniques can be an incredibly powerful, persuasive tactic. Therefore responsibility lies with the artist to make sure any modelling is deemed to be as physically accurate in all areas of investigation as possible, “In order for the archaeologists to benefit from computer-generated models and use them in a predictive manner, they must accurately simulate all the physical evidence from the site being reconstructed” [Devlin et al. 2001].
One of the most important areas of research in this respect is lighting. Rembrandt said that “All is light”, and within the commercial world of three dimensional graphics, film, television and photography, it is perhaps the most vital tool in conveying an emotional and physical response from the viewer. This is no different in archaeological representation, as without light there would be no scene and without accurate shadows and illumination, the way the viewers respond to what they see can be fundamentally affected, “if we are to avoid misleading impressions of a site, then the computer generated images should not only look ‘real’, but must simulate accurately all the physical evidence for the site being modelled” (Chalmers and Debattista 2005: 2). This dependence upon light is echoed by Chalmers and Stoddart (1996: 87), who state that, “In all image synthesis techniques, the fundamental step is computing the amount and nature of the light from the three-dimensional environment that reaches the eye from any given direction”.
Lighting was also essential for past societies, with one clear Neolitihic example visible in the Orkney Islands, where the site of Maeshowe is orientated to face the south-west, allowing light to spill into the monument only at the heart of winter. You can even see this phenomena occur if you follow the web stream present on their homepage and the countless recordings on their site. It has been suggested that this process relegates the rest of the year within to darkness beginning, “at the very point of midwinter solstice” (Richards 1996: 202) signalling the death of the old year and the ‘rebirth’ of a new year through illumination. Richards (1996) clarifies that at its construction, Maeshowe would have represented the landscape, fulfilling a role as a cultural and cosmological marker to its society. Consequently, light defines more than what people saw, it lies at the very heart of existence, influencing architecture and belief in a myriad of different ways, “Light in architecture is a complex phenomenon which penetrates every day practices and rituals” (Papadopoulos, C. & Sakellarakis, Y. 2010: 417).
In virtual imagery, this can be seen in the work of Gruber and Dobbins (2010), who used a Maya script to generate virtual daylight in a model of the ‘House of the drinking contest’ in Antioch. Speaking about their model, they note that the software was vital in analysing light at the site and that the ability to apply realistic, physical lighting based on global positioning would have many uses outside of their project (Gruber & Dobbins 2010: 422). Critically, their success in re-contextualising a series of mosaics using the technology allowed them to view and think about the scene in a way they cannot physically accomplish.
This desire for visual perspective is mirrored at the site of Çatalhöyük and it is a settlement where expression, experience and cosmology formed a valuable aspect of society. Therefore, if the remaining material culture could be placed into an interpretation of its original context, it could provide a great deal of information about life at a site, “of unique international significance” (www.catalhoyuk.com).
Aims: virtual accuracy at Çatalhöyük
This project will attempt to discuss just how reliable the Mental Ray rendering engine is at producing imagery that cannot just be potentially trusted visually, but also reinforced physically in its ability to generate light. Speaking about Mental Ray in 2007, Joep van der Steen comments that it is not only an engine with enormous potential, but possibly the best available at providing beautiful imagery with a respectable lighting solution. Consequently, whilst it may not be as efficient as other commercial rendering engines such as VRay and Brazil, the ability to provide realistic equations is why it is placed at the heart of this study. The features it contain extend to providing ‘accurate’ techniques for Global illumination, reflection/refraction, ray-tracing, area lights, bounced light and direct light.
Following preliminary contact regarding reconstruction work at the site of Çatalhöyük in Turkey, a desire for a stringent test of Mental Ray was needed to convince site director Ian Hodder into its potential as an analytical tool. The site boasts many conserved wall paintings, sculptures and other artifacts that are to be, “enhanced by virtual reality techniques and interactive video” (www.catalhoyuk.com) and then analysed in their original context using three-dimensional software. A reference image was provided of the onsite Neolithic House (below) and from this a ‘photo-realistic’, physically accurate render was expected, with lighting as the focus using a single daylight system to illuminate the entire scene. Future virtual study is critical if such a system could be relied upon to generate light accurately and from any global position. More importantly, proving the programs ability and precision is crucial in providing any other rendered work from Çatalhöyük with credibility, “if computer reconstructions are to go beyond mere digital images and models, and become a predictive tool for archaeologists, physically-based rendering techniques have to be used.” (Gutierrez et al 2008: 2).
To achieve this, a series of lighting techniques will be applied:
This study will then evaluate these stages to show exactly how much realism can be attained using Mental Ray lighting solutions, evaluating the positive and negative aspects of it’s technical and theoretical application in part two.
Alan Chalmers, Kurt Debattista, Investigating the Structural Validity of Virtual Reconstructions of Prehistoric Maltese Temples. VAST 2005: 6th International Symposium on Virtual Reality, Archaeology and Cultural Heritage. November 2005.
Chalmers, Alan , Stoddart, Simon. 1996 “Photo-Realistic Graphics for visualising archaeological site reconstructions” in, Imagining the Past: Electronic Imaging and Computer Graphics in Museums and Archaeology, Occasional Paper No.114, 1996. Pg. 85-94
Devlin, K. and Chalmers A. 2001. Realistic visualisation of the Pompeii frescoes. In Proceedings of the International Conference on Computer Graphics, Virtual Reality, Visualization, and Interactions in Africa (AFRIGRAPH). ACM, 43–47.
Diego Gutierrez, Veronica Sundstedt, Fermin Gomez, Alan Chalmers, Modeling Light Scattering for Cultural Heritage. ACM Journal on Computing and Cultural Heritage, 1(2). ISSN 1556-4673, pp. 1–15. October 2008
Gruber, E. , Dobbings, J. 2010 “Illuminating Historical Architecture: The House of the Drinking Contest at Antioch” in, Fusion of Cultures, Abstrats of the XXXVIII Conferenceon Computer Applications and Quantitative Methods in Archaeology Fco. JavierMelero, Pedro Cano & Jorge Revelles, Pgs 421-424
Papadopouslos, C. Sakellarakis, Y. 2010 “Virtual Windows to the Past: Reconstructing the ‘Ceramics Workshop’ at Zominthos, Crete” in, Fusion of Cultures, Abstrats of the XXXVIII Conference on Computer Applications and Quantitative Methods in Archaeology Fco. Javier Melero, Pedro Cano & Jorge Revelles, Pgs 417-420
Richards, C. 1996 “Monuments as Landscape: Creating the Centre of the World in Late Neolithic Orkney” in, World Archaeology vol. 28(2) pp. 190-208