Monday, 9 December 2013

Caldonazzo castle - from ruins to archaeological 3D reconstruction



In 2009 I met a technology called SfM, or Structure-from-Motion, where with a series of photographs and a kind of reverse engineering using the camera data, we could reconstruct the objects photographed in a cloud of points in three dimensions. After many studies realized, I saw it was not a trivial task to get good results, but I did not give up until I found a very interesting material in the ATOR's blog.


I already knew the impressive 123D Catch, but the goals with this technology were two. 1) Scanning objects in 3D using only free software and 2) The scan would need to have an accuracy of millimeters.

In ATOR's site I accessed excellent materials that enabled me to learn how the PPT-GUI work and achieve amazing results for me, at least at that time. Not so long ago, it was in May 2012.

As usual, I sent an email of thanks to the staff of ATOR and I took the opportunity to congratulate them for the excellent service presented in the posts. I told him that I was interested by their awesome field of archeology and was available if they needed anything related to 3D.


The answer came quickly and was very positive. The staff of Arc-Team research group and archaeological work, maintainers blog ACTOR, congratulated me for the work I developed with free software and invited me to write on the site, which I readily accepted. Moreover, they asked me if I was interested in participating in a project developed by them doing the reconstruction of a castle called Caldonazzo, where they work in their ruins. Second proposal also readily accepts. In that moment was born a partnership that lasts a year and a half and has yielded good fruits.

Caldonazzo



Caldonazzo is a tourist village located in Trentino, northern Italy. Famous for its lakes and mountains, houses a set of ruins of what has been a great castle, built between the twelfth and thirteenth centuries.

Since 2006 these ruins are the object of study under the responsibility of the Archaeological Superintendence of Trento, represented by Dr. Nicoletta Pisu.
The Arc-Team, a group to which I was built, aims to make the archaeological survey, organization of historical documents and was also tasked to scan the space in three dimensions, as well as rebuild it digitally. It is precisely this last part that comes into my work.

The Reconstruction



Despite my knowledge in architectural modeling, I had never worked with archaeological buildings. The challenge was to get something from nothing. Above we have the floorplan humanized and created from the 3D, but at the beginning of the modeling we did not we had a lot of information and the research for some features of the work would be changing as new references were found.

From Italy the staff of Arc-Team sent me via Dropbox all the data that were collected. Scans made ​​from photographs, notes on the works, the basic floor plans, facades, etc.

For facilitating the work I chose to use Inkscape to align elements scanned with plants and lay the ground for architectural modeling.

With the floorplan and placement of elements, sufficed to raise them in 3D.

I got the curves of the terrain and I converted into a mesh, that receive little by little the castle, so go already adapting all the terrain.
Not leaving some to follow the basic data of floor plans and cuts that I received from Italy.

Texturing was already set, together with the vegetation. When we work with architectural modeling, people expect the fastest possible visual results. Thus, the coloring and mapping of the scene, offer a preview of how it looks, keeping everyone motivated.


Once data arrived and internet modeling progressed, the part of the palace and also courtyard greenery received a modest humanization.

Details such as the configuration of the stairs was widely discussed, so that they represent a strategic tool of defense. In the case of the castle Caldonazzo, according to surveys, they relied on a retractable staircase for access to the tower. Thus, if the castle was invaded, the occupants would have to defend themselves shutting them in the tower. When storing the ladder, they hindered the access of the attackers inside the tower.

During the modeling of the castle courtyard area, was also worked to position the camera to show all the more didactic and elegant way possible.

After a few months of working, the outside of the palace was modeled completely, leaving only a few details to be completed. The main cameras were already positioned and humanization was complete.

The structure was ready, waiting for the footage taken by drones (look at the post about the filming that is very interesting!), to insert the castle virtually, through a technique called camera tracking, where the program captures the displacement of the real camera and transports it to the 3D scene. Thus, over a composite image can be fused real footage + 3D scene.

Some tests crossing photo + 3D scene had already been made​​, as the picture shown above, aiming to work the "color palette" of the real environment.

During the modeling of the outside of the castle, the data were collected and made ​​the refinements of the internal divisions of the building. With a floor plan ready, little by little were being composed indoor environments, both in the setting of furniture when lighting.

Above we have the dining room of the castle. Interestingly, the floor in question is not only of wood. Was placed mortar on the floor, much like the floors we have today, but matte. The wall, in contrast, has coated veneers.

Unlike a modern architectural modeling for internal purposes, such work is done with reference of documentary evidence. The artist does not do what he wants, or even what is more pleasing to the eye. He follows comments from archaeologists, who in their turn were guided by documents, pictures and the excavation of the site.

The kitchen had fairly simple accessories in relation to what we have today.

During the excavations, the staff of Arc-Team found some parts of the plaster wall belonging to the rooftop, where would the dorm. Using a graphic revolution, I created a graphic pattern to adorn the wall of 3D modeling.


The room was then modeled, always according to the observations of archaeologists.

To make viewing a most didactic work, was composed a cut lightweight prospect, covering the largest number of  environments. So we can have a good idea of ​​the building structure, scales and the like.

We also developed a blueprint to serve as the basis of presentation of the site and reconstruction. Always using Inkscape.

Once the footage was taken by drone, the time to cross the actual filmed scene with the scene vitual raised by scanning photogrammetry was reached.

The work is still in its start phase. Because it is a natural hill with irregularity it was a challenge to match the real scene with virtual scene.

Fortunately the process was facilitated by the robustness of tracking and compositing tools natively present in Blender. Above is an image with the scene in 3D view at left and rendered at right.



Now we have two different renderings representing boards. Note that the 3D scene fits the scene in the background, that it is the video.

At the beginning of the post was shown the results of previous studies of tracking. There is still much work ahead, but slowly we can get a good idea of how it was the palace Caldonazzo in its heyday and all done with free and open software.

I hope you enjoyed.

I leave here my thanks to Arc-Team for the opportunity to work with them in this fantastic project. I hope its the first of many. Grazie tante amici!

Bibliography:

Torre dei Sicconi: progetto di ricostruzione e valorizzazione di un antico sito castellare trentino (here in ResearchGate; here in Academia)
BlogItalia - La directory italiana dei blog Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.