# Scanning of Historical Clothes Using 3D Scanners: Comparison of Goals, Tools, and Methods
### Three-Dimensional Digitization Technologies  
Three-dimensional digitization of a real object can be understood as a process of translating the geometrical and visual features of the object's surface into a mathematical description. A 3D model can be perceived as a product of this process. Among the commonly used technological solutions for obtaining knowledge about these objects' features, we could mention the following:  
1. CAD modeling;
2. Touch scanning;
3. Laser scanning;
4. Structured light scanning;
5. Computerized tomography scanning;
6. Photogrammetry. CAD modeling might be perceived as a highly manual approach to producing a 3D model of a real object, in that a lot of human effort is needed to map the real object's geometrical and visual features to its 3D model. The other abovementioned solutions can be perceived as being more automated: they heavily utilize specialized algorithms that automatically recognize and reproduce the object's geometrical and visual properties in the form of a 3D model. The main disadvantage of CAD modeling, compared to the other mentioned solutions, becomes evident when the goal (and this is a very frequent one) is to obtain a 3D model offering an accurate representation of a real heritage object. More specifically, the disadvantage of CAD lies in the excess of freedom it provides in mapping the shape, such that the fidelity of the reconstruction can potentially be undermined. At the same time, striving to build a faithful model requires a significant amount of work and a high level of expertise from the creator. This type of approach is also used in heritage settings [11]; however, the resulting 3D model should be treated more as a representation of a given type of design than as a digital copy of a specific exhibit. The touch scanning technology uses devices that have an arm with a probe that makes physical contact with the object. When the object is touched, the position of the probe is read, which allows the device to record the exact 3D position of a given point on the object's surface. If samples are collected densely enough, it is possible to recreate the shape of the object with the required accuracy. However, exposing a fragile cultural heritage object to repeated contact with a hard probe risks potential damage. Although the accuracy of the obtained surface measurements is high, scanning by touching the surface of the object so as to reproduce every detail is extremely burdensome, and in some cases, even impossible. A further disadvantage of this solution is that no information is obtained regarding the color of the scanned surface. In laser scanning devices, the physical probe has been replaced with a laser beam. The device directs the beam to a specific point in space and captures the returning beam reflected from the object's surface. On the basis of the reflected beam's parameters, the distance to the reflection point can be calculated, indicating the position of a given surface point in space. Modern scanners also have an integrated camera that allows the colors to be read and matched at the designated 3D points. Modern scanners use Class 1 lasers operating in the infrared light band. Therefore, they do not adversely affect the surface of the scanned objects, unless it is particularly sensitive. Most often, scanners of this type provide a large scanning range and accuracy expressed in millimeters, and they are used to scan large cultural heritage objects (vehicles, buildings, and even entire historical sites) [12; 13; 14; 15; 16]. Structured light scanning involves devices that project an image onto the scanned object. The scanner projector displays an image containing a certain structure (most often fringes of different widths). The distortions of the fringes formed as the projection falls on the three-dimensional surface of the scanned object are captured by cameras that have been calibrated with the projector. The differences between the original and the captured image are used to calculate the topography of the object's surface in 3D.