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Virtual world heritage: More than three dimensional models


What this technology has enabled is the creation of models of cultural heritage by people who are not 'expert' in the object or precinct itself. These visualisations range from the very crude and useless (Figures 4a and b) to very photo-realistic (Figure 5e). The level of detail is not only dependent on the requirements of the project, but also on the intended interpretation of the model, and even whether it is to be viewed as a still image or an animation sequence. If the model is a record of what exists today, then it should truly represent that object with actual materials on the surfaces, and be proportionally correct (if it is leaning or in ruins, so be it). If the model is a reconstruction, then the materials should be what they would be at that time with appropriate wear and so on, and geometrically the objects may be in a more pristine shape.

Figure 2 A material map made from an actual texture Figure 3 A default library material



Figure 4a and b A material map derived from original photography in a simple 3d modelling package


Photorealism
A definition of photo-reality, when applied to computer visualisations, could quite simply be that the synthesised image should appear exactly as a photograph of the object it represents (or is intended to represent, a reconstructed cultural monument has no real world object to compare against). Expanding on this idea, Fleming (1998, p3) offers ten 'Principles of Photo-Realism' (of which he says an image should conform to at least eight in order to be considered photo-realistic):
  1. Clutter and chaos

  2. Personality and expectations

  3. Believability

  4. Surface texture

  5. Specularity 

  6. Dirt, dust and rust,

  7. Flaws scratches and dings,

  8. Bevelled edges

  9. Object material depth

  10. Radiosity
It could also be argued that in order to be photo-realistic, an image should also carry camera artefacts like depth of focus/field, lens flare and astigmatism. Modern computer graphics systems like 3D Studio Max offer the ability to create photo-realistic images both through complex methods of material mapping and through variables in the configuration of the render camera. Other software even facilitates the addition of camera artefacts, so it is entirely feasible to create a synthetic image indistinguishable from a photograph. However is this always what is necessary or beneficial?

Figure 5a-e. The Philippeion at Olympia, c200BC


Conclusion
The obvious question raised by the 4 images above is which better represents the Philippeion at Olympia? One could (should) also ask how was this reconstruction derived, were expert sources consulted, was it made from limestone, is the roof decoration generic or were remains found to verify their shape and colour? Is the purpose of the image to analyse the structure from an engineering perspective, or to show the grandeur of a lost civilisation? Why was it even created?

This paper has no answers to the questions, instead the intention has been to raise the questions in a forum specialising in the visualisation of cultural heritage. There is a need to eventually provide answers.

References

  • Fleming, W. 1998. 3D Photorealism Toolkit. John Wiley and Son. 328p

  • Kenderdine, S. C.L. Ogleby, J.A. Risetvski and K. Da Costa. 2000. 1000 years of the Ancient Olympics: Treasures of Ancient Greece. The digital reconstruction of Olympia, 3D Zeus and website. Proceedings of the 6th International Conference on Virtual systems and Multimedia. VSMM, Japan. 727p

  • Ogleby, C.L. 1999. From Rubble to Virtual Reality: Photogrammetry and the Virtual World of Ayutthaya, Thailand. The Photogrammetric Record. United Kingdon, 16:651-670

  • Piggott, S 1078. Antiquity Depicted: Aspects of Archeological Illustration. Thames and Hudson, 64p
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