The FIT master’s thesis brings a historic mill back to life

In the deep, rocky valley of the Oslava River between the villages of Ketkovice and Mohelno, tourists and hikers today pass by a fenced-off site. Few realize that they are standing in front of the grounds of a former watermill, which was a bustling hub of the region, especially during the First Republic. Ketkovice Mill, also known as Vydra’s Mill, stands in a deep valley below the ruins of Levnov Castle. It was likely built after 1300, probably at the same time as the castle, and soon passed, along with the surrounding villages, into the possession of the Lords of Lipá. It was a manorial mill with close ties to the nearby castle. In the 18th and 19th centuries, the mill changed hands frequently. A significant turning point came in 1826, when the mill passed into the hands of the Vydra family, after whom it is named. Under Bohumír Vydra—a miller and amateur landscape painter who took over the property in 1926—the complex underwent modernization and expansion. The improvements to the surrounding area included the installation of a decommissioned railroad bridge over the Oslava River and the reconstruction of the access road from Senorad. By 1930, both a mill and a sawmill—each powered by two overshot waterwheels—were in operation at the site, and the place had effectively become a small hub of civilization in the valley. Mill operations ceased shortly after World War II. Following Bohumír Vydra’s death in 1981, the property was divided into several parts. Today, it is a preserved private complex that is not open to the public—or at least, not yet. The Ketkovice Mill, which consists of several buildings including the millhouse itself and a barn, has become the subject of an exceptionally interesting thesis, the result of which is, among other things, the opportunity to take a virtual tour of the complex both in its current form and in its historical form from 1947.

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Drones, historical photographs, and a lot of work

“I first came across the Ketkovice Mill when I was looking through the list of thesis topics. Of all the possible assignments, the one that caught my attention the most was the one that included the historic mill,” says the author of the thesis, Peter Pločica, describing how he began his project. His thesis advisor is Prof. Martin Čadík. The thesis focuses on digitally documenting the Ketkovice Mill using photogrammetry—a method that creates 3D models of objects based on photographs taken from various angles. The mill and its surroundings were surveyed using a combination of a camera, a smartphone, and a drone, with the assistance of another FIT student, Tomáš Zaviačič. This allowed for the documentation of both the exterior surfaces of the buildings and parts of the interior. However, some areas—particularly the courtyard, the millrace, and so on—could not be documented with sufficient quality. The author of the thesis himself notes this: “The biggest challenge was documenting the mill itself. Since it is currently divided among five owners, it wasn’t easy to gain access to all parts of it, and as a result, I was unable to photograph some areas with the quality I had envisioned.” Creating the historical model was also challenging. For many parts, I had to rely solely on historical photographs and, based on them, reconstruct the building’s appearance practically from scratch. The mill’s owner, Mr. Olin Krištof, was a great help; he provided historical photographs and also arranged access to the mill itself.” The images were processed using COLMAP software. The result was several models represented by 3D points in space (so-called dense point clouds), which had to be cleaned of noise and outliers and merged into a single model. From the resulting point cloud, a polygonal model of the object was constructed using an algorithm. This was an exceptionally challenging part of the entire process, as confirmed by the thesis advisor, Martin Čadík: “Cleaning up the data was really a lot of work. The result was a model of the mill’s current state, and in order to show the interior, we had to model the entire mill all over again.” Subsequently, using available historical sources, a model corresponding to the state of the mill in 1947 was created in Blender. The photogrammetric model served here as a spatial template capturing the actual dimensions and shapes. Individual parts were modified or remodeled based on historical photographs and information from the current owner, as Pločica mentioned above. Windows, doors, the roof, the millrace with the millwheel, and the interior spaces with the milling system were all newly modeled. Textures corresponding to the building’s historical appearance were created or applied to all parts of the model. “The individual parts were also a challenge, such as the historic mill wheel, which no longer exists today and for which we had to rely on the current owner’s description,” comments Čadík on the progress of the work. He adds: “In my opinion, it’s a successful thesis project, which is why we’re happy to showcase it,” adds Čadík.

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In the final step, both models were used to create an interactive virtual tour in the Unity game engine. The application offers three modes for exploring the structure: a free tour of the historic mill, a free tour of the current state of the mill, and a guided, interactive tour of the milling process. The latter includes six stations and gradually guides the user through the entire process, from the arrival of a wagon loaded with grain in the courtyard to the final product.

We wish Peter Pločica, who will be moving from FIT to the private sector, every success. And here’s an offer for you: Would you like to take a walk through the grounds of the old mill in the Oslava Valley? Just click here.