TOTAL RECALL: A PLEA FOR REALISM IN MODELS OF THE PAST 
L. Van Gool^* *, M. Waelkens ^, P. Mueller“, T. Vereenooghe®, M. Vergauwen“ 
? ESAT-PSI/VISICS, Katholieke Universiteit Leuven, Kasteelpark Arenberg 10, B-3001 Leuven, Belgium - (vangool, 
vergauwen)(@esat.kuleuven.ac.be 
? Sagalassos Archaeological Research Project, Katholieke Universiteit Leuven, Blijde-Inkomststraat, B-3000 Leuven, 
Belgium - (marc.waelkens,tijl.vereenooghe)@arts.kuleuven.ac.be 
* ^D.ITET/BIWI, Swiss Federal Institute of Technology (ETH), Gloriastrasse 35, CH 8092, Zürich, Switzerland, - 
(vangool,pmueller)@vision.ce.ethz.ch 
Commission VI, WG V/2 
KEY WORDS: Cultural heritage, Archaeology, Vision, Reconstruction, Photo-realism 
ABSTRACT: 
Computer technologies make possible virtual reconstructions of ancient structures. In this paper we give a concise overview of the 
techniques we have used to build a detailed 3D model of the Antonine nymphaeum at the Sagalassos excavation site. These include 
techniques for 3D acquisition, texture modelling and synthesis, data clean-up, and visualisation. Our aim has been to build a 
maximally realistic but also veridical model. The paper is also meant as a plea to include such levels of detail into models where the 
data allow it. There is an ongoing debate whether high levels of detail, and photo-realistic visualisation for that matter, are desirable 
in the first place. Indeed, detailed models combined with photo-realistic rendering may convey an impression of reality, whereas they 
can never represent the situation like it really was. Of course, we agree that filling in completely hypothetical structures may be more 
misleading than it is informative. On the other hand, often good indications about these structures, or even actual fragments thereof, 
may be available. Leaving out any structures one is not absolutely sure about, combining basic geometric primitives, or adopting 
copy-and-paste methods — all aspects regularly found with simple model building — also entail dangers. Such models may fail to 
generate interest with the public and also if they do, may fail to illustrate ornamental sophistication or shape and pattern irregularities. 
1. INTRODUCTION 
Virtual 3D models of monuments and constructions that have 
largely disappeared offer great potential They are useful to 
scholars as a basis for discussion and hypothesis verification, 
and are an effective presentation to the public of their cultural 
heritage. This said, the level of precision and photo-realism at 
which one ought to try and produce such reconstructions is 
disputed. Some warn that the more compelling a reconstruction 
is, the more the general public may take the correctness of cvery 
detail for granted, even if part of the reconstruction is based on 
not much more than a dedicated guess or one among several 
hypotheses. 
We recognise the relevance of these caveats concerning high 
visual realism. It should for instance remain possible to 
visualise the levels of uncertainty in the different aspects of the 
reconstruction. Rationales behind particular completions and 
choices should be documented, preferably also as annotations to 
the model, so that users have direct and easy access. These 
issues have also been raised by (Forte, 2000), a pioneer in 3D 
modeling of cultural heritage: *Noticeable gaps are represented 
by the fact that the models are not ‘transparent’ in respect to the 
initial information (what were the initial data?) and by the use of 
peremptory single reconstruction without offering alternatives’. 
Yet, we see at least as big a danger in oversimplified models, 
  
* Corresponding author. 
and this is what the alternative has often turned out to be in 
practice. These can be misleading in at least two ways. 
On the one hand, copy-and-paste strategies have been popular in 
the production of such models, but these create unrealistic 
regularity in shapes or patterns. This may convey a false 
impression of technological sophistication. Also, such models 
tend to be produced by starting from a library of predefined, 
geometric primitives. Perfectly planar walls, precisely 
cylindrical arches and pillars, repetitions of identical tiles or 
decoration, etc. tend to be a far cry from actual variations in 
handcrafted elements. 
On the other hand, omissions could have the opposite effect in 
that they often fail to do justice to the true level of decoration of 
a structure or to the intentions of its creators. One can leave out 
colors on Greek buildings, for instance, thereby perpetuating 
one of the most persistent misconceptions about their original 
appearance. Even if there may be uncertainty about which color 
ought to go where, making occasional mistakes in the coloration 
may well be the lesser evil. Similarly, even if one is not 
absolutely certain about the ornamentation found in certain 
parts of a building, it may be better to make a dedicated guess at 
its original state than to simply leave it out. Quoting (Barcelo. 
2000): *VR is the modern version of the artist that gave a 
‘possible’ reconstruction using water-colours’. One only has to 
think of the Halicarnassos mausoleum to have a vivid example 
  
  
  
   
  
   
  
   
   
   
  
   
  
  
  
  
   
  
  
   
   
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
   
   
   
   
  
   
  
  
  
  
   
  
   
   
   
   
   
  
  
   
  
  
  
     
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