3D scanning of exhibits from the County Museum in Nysa

St. Anna Samotrzecia, XVI / XVII century, Silesia. Linden wood sculpture, polychrome on mortar, height 50 cm, width 30 cm.

The full-plastic polychrome sculpture shows St. Anna, the mother of Mary and baby Jesus. This three-figure composition was one of the most popular in medieval iconography. She was understood as a symbol of the Immaculate Conception (Immaculata conceptio) - Mary, conceived after Joachim and Anna's childlessness for many years - after the Annunciation by an angel, was born free from Original Sin and therefore could become the Mother of God. The sculpture from the collection of the County Museum in Nysa shows the enthroned St. Anna, shown frontally, holding her grandson on her lap, embracing both the Child and her daughter reading the Bible, standing right at her feet. The sculpture does not have the proportions of the figures, which was characteristic of the late Middle Ages, but the physiognomy of each figure, the gaze of St. Anna and Mary emphasize the attempt to convey the mysticism of Immaculata conceptio.

Madonna on the globe - Immaculata, 17th / 18th century, Spain (?). Wooden, polychrome, silvered sculpture, Madonna's eyes and putti made of white glass, a globe covered with a map made on paper, 100 cm high, 52 cm wide

The full-plastic polychrome wooden sculpture shows the young Mary in a characteristic view - on the globe. This iconographic motif called Immaculata, that is, the Immaculate Conception of Mary, was identified with the Woman of the Apocalypse of St. John (Then a great sign appeared in heaven: the woman with mandorla 'clothed with the sun' and the moon under her feet, and on her head a crown of twelve stars (Rev 12: 1)).

Immaculata was shown as a young, beautiful girl, in a white dress and blue cloak, with her hands folded in prayer, which is significant without the Baby Jesus. Mary was depicted on a cloud, a crescent moon, a globe, with a serpent under her feet, surrounded by a luminous mandorla or a crown of stars adored by angels. The sculpture from the Nysa collection represents exactly the Mary pattern popular for the Baroque and Rococo periods, but interestingly enough, the globe is entirely covered with a map made by French cartographers, showing Spain as the world. More info on page The County Museum in Nysa.

Among the many devices offered by GLOBAL3D, the Thor 3D Calibry scanner with a built-in texture camera was selected, thanks to which capturing such an important element as polychrome was not the slightest problem.

The Calibry 3D scanner is a device designed to scan medium and large objects. The manufacturer ensures that the device is able to scan objects with dimensions ranging from 0.2 m to 10 m, including the possibility of scanning human figures, which are often very difficult to scan. So it is a universal device that will work in every industry, starting from the broadly understood protection of cultural goods, architecture, designing, prototyping, creating models for games or films in medicine and heavy industry.

A 3D scanner is a device that analyzes an object or its surroundings in order to collect / collect information about its shape or appearance (textural scanning) in order to create the most accurate three-dimensional digital model, thanks to which we are able to carry out the actions we need (prototyping, quality control, reverse engineering). Due to the light emitted by the scanner, used for data acquisition, devices can be divided into two types.

1. Scanners in which the light source is a diode or multiple LEDs emitting structured light.

2. Scanners in which the light source is a laser.

It cannot be unequivocally stated that either of these two types of scanner operation mechanisms is better or worse. Each of them, when properly used, will fulfill its task to the best possible degree. However, one should bear in mind the limitations of both, which we will deal with later. For now, let's focus on the basic principles of the work of these two types of devices.

1. Scanners in which the light source is a diode or multiple LEDs emitting structured light.

Structured light scanners display a pattern of light on the scanned object. Selection patterns are tracked by a single camera or multiple cameras simultaneously. Color capture is also available using a special camera. The light pattern is created using light modulators.

The structured light 3D scanner can capture large size in seconds and also guarantees a high level of accuracy and high resolution. The light source is not dangerous to human eyesight, so structured light scanning technology can be used to scan people. Structured light scanners can be mounted on a stand for stationary scanning as well as used in manual mode. However, they are sensitive to ambient lighting conditions and have problems scanning glossy and dark objects.

2. Scanners in which the light source is a laser.

Laser scanning works by projecting a laser point, beam, or multiple beams onto an object and then capturing the laser reflections with sensors. The main advantage of laser scanning is that it can achieve high resolution and accuracy. It is also less sensitive to ambient light and is better suited for scanning shiny or dark surfaces.

Most of these types of scanners are handheld. Although they do better than structured light scanners when scanning glossy and dark objects, they have a problem with scanning transparent or transparent objects nonetheless.

It can be noticed that the use of 3D scanners in the broadly understood protection of cultural goods is a recently gaining popularity trend. The technology of creating virtual 3D models allows for archiving, recording or digital display of exhibits that under normal circumstances do not fit into the exhibition rooms. This is important in the case of museums, as more exhibits can be made available to "virtual visitors" without the need to engage significant forces. Another advantage is the possibility of digitizing the entire conservation and restoration process of individual exhibits in order to increase the awareness of visitors and enrich their knowledge of the works performed in museum conservation studios.

Due to the fact that 3D scanners are devices with high accuracy, in the case of the Calibra scanner it is about 0.5 mm, it is possible to create models as illustrative materials, e.g. in conducting preliminary conservation research consisting in assessing the state of preservation, creating maps of polychrome on the object or pollution or with the use of post-processing software, preparation of the proposed restorations, or the selection of colors when marking the polychrome. These are just a few of the possibilities offered by the 3D scanning technology and only in the edition of handheld scanners designed for scanning small and medium objects (in the case of a 3D scanner this value is from 0.2m to 10m). There are also many other scanners designed to scan entire rooms as well as digitize large areas of archaeological excavations, however, in this article, let's stick to scanning small and medium-sized objects.

Coming back to scanning sculptures in the County Museum in Nysa. Both sculptures were scanned in the exhibition halls without any special preparations. Although scanners do not perform very well in bright rooms and with spot lighting on an object, the conditions in most museums seem to be ideal for such work. Large rooms, largely diffused lighting, easy access to the exhibits from all sides are undoubtedly great advantages that people involved in 3D scanning cannot underestimate. Rooms such as a conservation studio or a warehouse / archives also meet the basic requirements for working with a 3D scanner.

To scan the above-mentioned objects, the basic Calibry Human scanning profile was used, in which the scan accuracy was set at 1mm, although the scanner itself offers even 0.1 mm. The other scanner settings were based on obtaining the best possible texture quality. Objects were scanned on the basis of texture capture as well as object geometry capture. It is a proven method in the case of objects composed of a large number of textured surfaces and with complex geometry (human silhouettes are a perfect example of this). During the scanning process, apart from capturing information about the model, the 3D scanner takes a photo of the object's texture every few frames, and then the algorithm weaves them in the right place.

The model itself in the case of the Calibra scanner is not created in real time, but requires setting parameters that affect the quality of the scan and its accuracy. The manufacturer has provided a few basic profiles that can be used depending on the scanned object. However, due to the high openness of the Calibry Nest software, we can create new profiles ourselves, thanks to which we save time when we scan several objects similar to each other.

After creating a virtual model of the scanned object, using the implemented editing tools, we can carry out a number of operations thanks to which we will be able to, for example: remove accidental objects captured during scanning, patch holes - resulting from failure to scan one of the planes on the object, smooth the model surfaces, reduce or increase the number of triangles the model is made of, make measurements.

When the editing stage is finished, although we are not satisfied with our work and we have other scans of the same object, we can carry out the process of overlapping the scans to achieve the best final results. This process consists in selecting a few or a dozen common points on the surface of the models and then the program's algorithm adjusts both scans. The more common points we choose, the greater the accuracy of the connection. It is important that the common points are as far apart as possible during the joining process. Thanks to this, the folding algorithm will not get lost.

The Calibra scanner in this respect surpasses its competition, in the software, which we can most often determine three such points. This fact is very important when we want to obtain high accuracy of scans.

After all the above-mentioned processes, we can start texturing the object. As mentioned earlier, the algorithm imposes a colored texture on the working model using color photos taken while scanning the object. As in the case of creating the model, texturing, or rather the speed of this task, depends on the computing power of the computer. With a mid-range computer, this time does not exceed 2-3 minutes.

After finishing work with the scanner and its software, the created 3D model undergoes the process of color correction and brightness and sharpness correction in the Calibry Nest software editor and if we are satisfied, we can finish the work.

Below are the results of scanning objects:

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