2. EXISTING WORK
2.1 Objectives
This scientific project is included in a global scheme. The Idea is
to reinforce Thann’s attractiveness thanks to cultural means. This
research is a first step. Creating an accurate Geographic
Information System (GIS) and a 3D model of the site appcars to
be really useful for archaeologists or historians but also for the
city itself. The goals of a first project were to acquire data and to
build the GIS and the 3D model. A perspective of the project was
the integration of a virtual tour of the site. This simple
application created thanks to panoramas (made of pictures) was
really efficient in terms of visualization and distant
comprehension of the site. It is also crucial to be aware of the
people we are working for. The GIS and the 3D model are very
useful tools. However, the city head is looking for casy ways to
make people discover the site and find disseminate information
about it. The issue at stake here was to find out how to create an
application that is not only accessible to everyone but also
combines all different types of data (archacological works and
reports, pictures, 3D, 2D, etc.).
2.2 Data: surveying and treatment
First of all, the team had to acquire data by photogrammetry and
TLS techniques. Then, after the treatment, a 3D model was
created. The model is structured in layers and coded colours.
Each sector is numbered and identified according to its position
and function as the description given by Ehretsmann.
Identification is then used to associate any type of data in digital
form (drawing, photography, mode of assembly, drawing,
collecting descriptive report, hyperlink to web page, etc.) to each
constitutive element of the ruins.
This structure is very important for the case of model integration
into an Archaeological Knowledge Information System (AKIS)
especially in 3D-AKIS. The analysis capabilities of 3D-AKIS
combined with a high performing documentation management
system was used here to provide a tool for archiving and
documentation, allowing full analysis of the complex structure.
(Koehl at all, 2011).
The Figure 1 shows the different steps to acquire all types of
data, from the onsite survey to the 3D model and to the GIS,
from existing 2D data to 3D vector data.
2.3 Virtual tour
The first virtual tour was created. It was quite simple, 12
panoramas made of pictures were linked to each other in a flash
application which is readable in Adobe flash player. The link
between the different scenes is available through hotspots. You
can also switch from a panorama to another thanks to a Combo
Box at the top of the viewer. This tour was created by means of
the Kolor Panotour software. The used standard version was
easy to exploit. A graphic interface helps the user to import
panoramas and to create links between each of them. However,
this version remains a bit limited. It is not possible to add any
features. As a user of the standard version, it is not possible to
get the XML file for adding exterior parameter. Those features
are only available in the professional version.
The issue at stake here was to develop this existing tour. First of
all the question was: how is possible to integrate the 3D model
into the tour? To solve that problem we suggest the creation of
panoramas from the 3D model.
virtual tour
integration to the Flash Data, SWE
30 model integration to the
creation
Figure 1. Scheme of data (origin and treatment)
3. CREATING PANORAMAS: COMPUTER VISION
BASICS
A definition of a panorama could be a view with a large angle.
The concept is used in photography, in painting, drawing and
also in cinema. There are many types of panoramas and several
software packages (Kolor, 2012), (PTgui, 2012), (Hugin, 2012)
are now quite developed to create them.
It is important to see the different types of panoramas, the data
needed to create them, and how they are created, manually or
automatically. In this part, we will give several examples of
panoramas (with different formats) and explain a few basics to
understand how they are created in software.
There are plenty of formats. The projection depends on the way
the pictures of the scenes were taken, on the software used, or on
the expected special effects. In some specific application, the use
of any tie points is not required. For instance, it is possible to use
a cubic projection if the panorama is generated thanks to six cube
faces. There are other types of projections: the stereographic one,
also called “little planet" that has the ground in the middle of the
picture and the sky on the edges.
The examples below are just a few of them, extracted from the
web site (Wiki.panotools, 2012) and the most cited in the
literature.
Full Spherical Formats: There arc two main spherical formats:
Equirectangular and Cubic. Both are able to display the whole
sphere that surrounds us - 360? along the horizon, 90? up and
90? down. Specialized viewers are needed to view spherical
panoramas. Kolor Autopano is able to do it.
Equirectangular Format is widely used by à couple of
Panorama Viewers as for example PTViewer and SPi-V. It
consists of a single image with an aspect ratio of 2:1 (that is, the
width must be exactly twice the height).
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