CIPA 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey
The user, taking into account the unevenness of the surface to
be measured and the degree of accuracy desired, will be able to
establish the size of the tessella, resulting in a network which
could be more or less dense which will adapt to the surfaces of
the object quite accurately. Once this lattice has been obtained
the software will allow to calculate the approximation of the
volume of the original figure as the summation of the partial
volumes of prisms whose bases are each one of the grid squares
and heights are the average of its four corner elevations.
By applying this technique we could calculate the volume of
the loss of matter caused by weathering processes. If it is
possible to rebuild (draw) the original shape particular to one
piece, we will be able to obtain a digital model of its surface
and facing to the model resulting from its current estate,
obtained from the restitution, we will be able to obtain the
volume between both states (Fig. 5).
5.3 Deformation maps.
One of the main aims of the terrain digital modelling
programmes is that of obtaining, in an automatic way, a
representation of the relief through contour levels, that is to say,
maps of isohyets. These should make reference, in the case of
terrains, to a particular altitude origin. If we make this
application extensive to a given flat surface, we will be able to
obtain a map of isohyets representing how the surfaces differ
from that of reference (ideal plan) as if they were elevations of
the ground surface. These maps can be drawn with different
colours to highlight its expressive power this is an excellent
way to represent areas which have been deformed or thrown out
of plump.
Figure 6. Colour depth map.
The assessment of the degree of strain on the whole plan and
not in isolated spots allows for a more accurate diagnosis of the
nature of the cause.
The same technique will allow us to represent any quantitative
variable that has relevant spatial distribution. For example, if
the elevation is substituted by the degree of humidity in several
spots in the façade, we will obtain a map of the humid areas,
etc.
5.4 Simulation of shades, ilumination
testing.
The surface digital models obtained have
been applied to the illumination project of
the aqueduct. The triangle mesh
reproduces the textural features of the
surfaces of the ashlars and above all the
combination of the rusticated volumes of
their sides and the joints between the
ashlars. This makes it possible to emulate
the effect of the different ways of
illuminating the given monument to
enhance the chiaroscuro effect. Ways of
illuminating differentiated not only the
configuration and nature of light beams
(colour, intensity, fuzziness, amplitude)
but also by the spatial distribution of any
number of sources.
Figure 7. Solar Shadows simulation.
5.5 Creating anaglyphs.
An interesting product derived from the digital surface models
are anaglyphic stereograms. These are stereo pairs of images in
which each image is shown using a different colour. The two
images are overlapped and then viewed using red/green or
red/blue glasses (depending on the colours used). This means
that the colour channel is used for the stereo separation and
therefore the perception of anaglyphs is monochrome (black
and white), although colour anaglyphs can be made.
Figure 8. Anaglyphic stereogram, (use red-blue glasses)
