Rock hewn architecture survey. The problem of construction of the geometrical model

This article is focused on the transformation of the numerical data from laser scanning or image-based modeling in a geometrical model based on known geometric forms. During an international research on rock hewn architecture in Italy and Cappadocia, we made laser scans of some important medieval rock hewn churches. Once the phase of data acquisition is concluded, it is usually followed by the creation of a numerical model (points or mesh) which describes the morphological state of the subject. It is however known that survey is not a mere “registration” of data, but it is a “critical” operation of interpretation that shows the features considered necessary by the surveyor to describe a certain aspect of the subject. An operation usually made on the numerical model is its translation in geometric model: cubes, cylinders, tori, figures generated by translation or rotation; the subject is divided in elements which help its spatial understanding and may show the formal intention of the design process. However, while “built” traditional architecture - realized by elements overlapping - is more easily referable to simple geometric forms, rock hewn architecture, like sculpture, is realized by subtraction of material, and needs the identification of forms “similar” to known elements (vaults, floors, ramps, etc.), to allow the recognition of its forms. In the “translation” of the rock hewn form, into geometric model we therefore need to find a suitable form of geometrization. On the base of the numerical models we want to investigate on the creation of simpler geometrical models which allow the morphological analysis and the comprehension of the physical realization, based on a “geometric” project, in the field of rock hewn architecture. Keywords: survey, laser scanner, point clouds, mesh, 3D geometrical model, Göreme.