CIPA 2005 XX International Symposium, 26 September - 01 October, 2005, Torino, Italy 
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automatic way. The survey of the cloister vault of the Sala del 
Trono has been realized by acquisition of clouds of points with 
the laser scanner LEICA HDS3000 instruments, with a 4 mm a 
6 m resolution (Figure 9). From the cloud of points and from 
the model the aim is extracting those information that describe 
the structures and the building genesis of the examined object 
(Figure 10-11). 
mzmmmKmmmmmmmmmHmmmm**** kms mm**-, » ■.«« 
... .<.«»■« 
Figure 9. Georeferentation of the cloud of points in the net 
system of the Villa Reale (Gauss Boaga uncontracted 
coordinates) with topographically surveyed architectonic points 
2.1 Genesis and building models 
A typical pavilion vault is generated by two barrel vaults with 
an identical guiding curve. By cutting the barrel vault on a 
square plant with two vertical and diagonal planes, four two by 
two identical parts of a vault are the result. 
This kind of vault will be a semi-cylindrical curving one, a flat 
or raised one, a vault with an elliptical directrix, etc, according 
to the barrel vault which it comes from (Figure 10). 
2.2 3D model realized beginning from clouds 
In this case, the aim is to realize a 3D orthophoto model 
characterized by a metric resolution compatible with the 1:50 
scale, but also by a radiometric-photographic resolution 
compatible with the 1:20 scale. This model may represent a 
support for the geometric, constructive, thematic and 
morphological knowledge of the building and a foundation for 
the required interdisciplinary analysis. 
The elaborated model enables to map the materials, the 
building conditions and the causes of deterioration-instability 
and it helps the reading on paper and on video of architectonical 
and decorative details. These data are used by planners and 
restorers to define the intervention projects and to study the 
object morphology. 
According to this view, an experimentation on distinct fields 
has begun in order to test different instruments and 
methodologies able to extract, from clouds of laser points, the 
structural elements of a surveyed object, such as discontinuity 
lines, edges, vault guiding lines. From these clouds, after having 
them opportunely processed with cleaning and filtering 
algorithms, it is possible to elaborate a digital model of the 
surface (DSM), extract profiles and sections, where major and 
primal planes are. The Cyclone and Cloudworks softwares have 
been used, whose functionalities have been tested: 
extraction of sections as “points stripe” 
semi-automatic extraction of sections as line in the 
space or plane 
These experimentations serve as tests to understand which is the 
best way to be followed in order to implement the modeling. 
In the case of the Sala del Trono, it is better to separate the 
geometric aspect of the building from the ornamental decorative 
apparatus represented by the wood boiserie, the wall stuccos 
and the vaulted elements in the intradossal part. 
But also simplifying, it has been clear that the genesis of a 
pavilion is not sufficiently approachable to reality only by 
means of the guiding sections of the two barrel vaults (in this 
case elliptical). 
This fact is to be attributed to the dyscrasia between the 
theoretical model (Figura 10) and its factual realization by 
means of the centerings. This required that, also in the 
simplified model, the elliptical diagonal sections - lines of 
discontinuity between the two intersecting models (Figure 10) 
had to be taken into account. 
During the elaboration of laser points, it can also be useful to 
find not only the structural section, but also, in order to 
represent also the even simplified decorative apparatus, the 
curve that approximates the outline of the points without 
passing obligatorily through all of them. 
This because the points given back by the laser instrument are 
affected by the error caused by the non-uniform response to the 
signal of the object surface and also because they are not 
sufficient to represent in a “veritable” form of the discontinuous 
detail of the stuccos. 
Thus the outline is very unordered, also because of the object 
actual morphology. These information, which can be defined 
qualitative, can also be considered and reproduced later on if a 
detail analysis is required (lower part of the Figure 10). 
Figure 10. Geometric diagram of the pavilion vault: the parts 
indicated with the number 1 are called “spindles” and the parts 
indicated with the number 2 “nails”. By assembling four 
spindles, a pavilion vault on a square plant is generated