The reconstruction of the altar

Hi all,

Today I am going to talk about the process of digital reconstruction and restoration of the altar of Cim basilica.

According to the diary of the archaeological excavation, pieces of two altars had been found in the terrain around the basilica. They both were altar table, the first one was in marble, while the second was in lime stone. Fragments of the two tabulae and of the columns of support were founded. Today they are preserved in Mostar, at the Museum of Herzegovina.

Fragments from the marble altar (Photo from Anđelć 1974)

Fragments from the marble altar (Photo from Anđelć 1974)

Reconstruction of the marble altar (Drawing by Slobodan Kudra, from Anđelć 1974)

Reconstruction of the marble altar (Drawing by Slobodan Kudra, from Anđelć 1974)

I firstly focused on the reconstruction of the marble altar, as its engraved capitals offered the opportunity to study and develop a suitable methodology of digital restoration.

Marble capital (Photo by Tatjana Mijatovic)

Marble capital (Photo by Tatjana Mijatovic)

As the engraved motif is quite easy to be copied, the first idea was to sculpt the capital using the sculpting tools of Blender. Even if the result was not far from the original, it was not satisfactory from a conceptual point of view. It is indeed important to consider the virtual reconstruction of the capital as a restoration process and not as a simple 3D modelling. This distinction entails some important consequences in the elaboration of the procedure. In the restoration process, the most important principle to follow is to preserve the authenticity of the object: the restorer has the duty to safeguard its originality. Although the digital restoration does not imply any intervention on the real object, it has indeed to respect its identity.

Capital sculpted in Blender

Capital sculpted in Blender

For this reason I came up with a second approach and I started the restoration of the capital from its pictures. Tatjana Mijatovic, from the National Museum of Herzegovina in Sarajevo, prepared the documentation for our work and took several pictures of the capital in the museum. By using Blender I created a 3D model of the basic shape of the capital, paying great attention to the arrangement of the polygons in the mesh. It is indeed very important to create a regular geometry in order to obtain a smooth result when subdivision modifiers are applied to the mesh.

Then I created the depth map of the decoration by using Photoshop and I imported the result in Blender, where I used the black and white image as a displacement map.

Capital: Geometry of the mesh and UV mapping in Blender

Capital: Geometry of the mesh and UV mapping in Blender

The result was a 3D model that perfectly corresponded to the real object. As the geometry of this model was too high to be used in a real time application I reduced it by using Meshlab, an open source system for the processing and editing of 3D meshes.

Capital. Final 3D model in Blender

Capital. Final 3D model in Blender

Once the 3D model of the capital was ready, I moved on the reconstruction of the remaining parts of the altar.

Thanks to the diary of the archaeological excavation and the images published by Anđelć in 1974, we know what the original design of the bases of the columns was. Unfortunately only a partial fragment was available in the museum to be photographed for our work.

Marble base (Photo by Tatjana Mijatovic)

Marble base (Photo by Tatjana Mijatovic)

The first step in the restoration process, then, was to reconstruct the contour of the column in Photoshop.  Then, by using the result image as a model, I designed it in Blender.

Column outline. Reconstruction in Photoshop (left) and in Blender (right).

Column outline. Reconstruction in Photoshop (left) and in Blender (right).

By revolving the outline I obtained the decoration of the base of the column, then I modelled the rest of it.

Here you can see the reconstruction of the whole altar.

Digital restoration and final reconstruction of the marble altar of Cim basilica.

Digital restoration and final reconstruction of the marble altar of Cim basilica.

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