International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XL-5/W2, 2013 
XXIV International CIPA Symposium, 2 — 6 September 2013, Strasbourg, France 
PHOTOGRAPHER-FRIENDLY WORK-FLOWS 
FOR IMAGE-BASED MODELLING OF HERITAGE ARTEFACTS 
N. Martin-Beaumont ?, N. Nony ?, B. Deshayes^, M. Pierrot-Deseilligny*, L. De Luca ? 
? MAP-GAMSAU, UMR CNRS/MCC 3495, École d'architecture, Marseille, France — 
(nicolas.martin-beaumont, nicolas.nony, livio.deluca)@map.archi.fr 
b RMN — Grand Palais, Paris, France — benoit.deshayes@rmngp.fr 
‘ENSG, Marne la Vallée, France — Marc.Pierrot-Deseilligny@ensg.eu 
KEY WORDS: Photogrammetry, image-based modelling, methodology, 3D documentation, photography, photographer 
ABSTRACT: 
Because of its low-cost and ease in use, 3D reconstruction from sets of images has an great potential for enhancing cultural heritage 
documentation, conservation and valuation. However, these technologies, from image acquisition to final 3D model obtaining, are 
often difficult to master for non-expert people. Our work consists in developing a series of acquisition protocols for the museum's 
photographs. The end-goal being to enable those professionals to generate efficiently and easily 3D models of heritage artefact. 
1.INTRODUCTION 
Since the recent convergence of the researches in the fields of 
photogrammetry and computer vision, photogrammetric results 
relevant for the documentation and the study of heritage 
artefacts (archaeological fragments, paintings, sculptures, 
furnitures, architectural elements, buildings, sites) can be 
computed with high quality photographs without others data, 
through the APERO and MICMAC pipeline for example 
(Pierrot-Deseilligny, 2011). 
How to precisely define this quality? There is both a 
photographic quality (definition of the picture, sharpness, 
dynamic range, etc.) and the correct setting of parameters linked 
with the image-based modelling constraints, especially the 
spatial configuration of the points of view. 
Nonetheless the settling of these parameters cannot be the same 
for all cases since the artefacts have very different 
characteristics. Thus the whole corpus must be divided within a 
technical typology including morphology, scale, brightness, 
etc.. Each group of these classifications lead the photographers 
to a suitable protocol. It explains how to choose the different 
points of view, how to enlighten the artefact, etc.. 
The photographs taken are then processed with the web 
interface on cloud. The whole pipeline, including 
photogrammetric acquisition, data processing, data indexing and 
data exploitation is the aim of the Culture 3D Clouds: 
synthesize technical solutions for 3D surveying. 
New businesses and technical models can emerge in the 
institutions that houses and cares for collections of artefacts. 
The photographer working in these institutions could learn and 
develop a practice of photogrammetry. 
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CONSTRAINTS 
The combined computer vision/photogrammetry approach of 
APERO for estimation of initial solution allows a certain 
flexibility in the data acquisition, for example a leeway in 
choosing the points of view. The photographers can even shoot 
without a tripod if the shutting time allows it. 
The automatic process consists in tie-points extraction (with 
SIFT algorithm), internal and external orientation by bundle 
adjustment (Apero), and dense image matching (Micmac). The 
final output is a set dense and accurate pointclouds. 
However in order to make the relative orientation converge and 
to produce precise results, some constraints have to be 
respected: 
* for each desired points cloud take a “master” image 
and several closed associated images (with low ratio 
base to distance and important overlapping) 
(Pierrot-Deseilligny, 2011), 
between each master image take a sufficient number 
of intermediary images to assure the connection 
during the orientation step (Pierrot-Deseilligny, 2011), 
avoid to move a punctual light source during the 
photographs acquisition, 
use a context with enough details spread in all the 
space photographed as background, 
fix as many parameters of the cameras as possible. 
The cultural heritage aspect introduces others constraints: 
* put a metric reference in the scene as scale, 
compute relevant surface description for the whole (at 
least the maximal) surface of the artefact with a 
sufficient resolution for its study. 
reproduce all the photometric values of the artefact, 
control the lighting and the digital capture for a 
colorimetric (or radiometric) study of the artefact, 
long-term archive the photographs and the results. 
These different constraints can sometimes be contradictory. For 
example the optimal way of enlightenment for colour 
reproduction can be different than the one for the dense 
image-matching. This is why several solutions coexist, even for 
the same artefact.