## 2 Materials and Methods
### Reverse Engineering Techniques and Technologies  
A plethora of techniques and technologies are at one's disposal when undertaking the reverse engineering process, which can be applied to a multitude of practical applications. It is imperative to draw distinctions between the definitions of \"reverse engineering technique\" and \"reverse engineering technology\". The term \"reverse engineering technique\" denotes the fundamental principle that underlies a specific digitization process. The term \"reverse engineering technology\" encompasses technological devices utilizing distinct techniques. Reverse engineering techniques are based on two main principles, which are used in object digitization. These principles are contact and non-contact acquisition of point coordinates. This is illustrated in Figure 2. Direct contact technologies involve the acquisition of surface data of the digitized object through physical contact between the contact sensor of the technology and the surface of the digitized object. The most widely used example of this principle for obtaining surface point coordinates is the Coordinate Measuring Machine (CMM). The primary advantage of this system is its ability to achieve surface measurement with a high degree of accuracy. However, this method is not without drawbacks, including the necessity of employing fixtures to position the digitized objects correctly, the limitation to specific points for measurement, the requirement for an environment free from disturbances, and the consequent reduction in digitization speed [17; 19]. Figure 1: Stages of digitization in reverse engineering. Non-contact, or non-direct, digitizing devices eschew the use of physical proximity and contact with the surface of the digitized object. Rather, they employ mathematical and physical laws as the underlying principles of these techniques. Within the framework of the non-direct principle of digitization, two distinct techniques can be distinguished: reflective and transmissive. The transmissive techniques are predicated on the laws of wave transmission through materials with different physical properties, the best known of which are magnetic resonance imaging and computed tomography, which are widely used in the medical field [17]. In the domain of object digitization, the predominant technologies are those grounded in the physical principles of ray and wave reflection from object surfaces. Conversely, non-optical techniques rely on the physical laws of wave reflection from surfaces during the process of surface digitization. Examples of such techniques include sonar and microwave radar. In contrast, the domain of optical digitization relies on the physical laws that govern the reflection of light rays from the object's surface. It is important to note that there are two primary categories of optical digitizing techniques: active and passive. Passive optical techniques rely on ambient light, eschewing the use of a light beam source by the digitizing devices for data acquisition. The aforementioned techniques are based on surface computation using camera position change imaging Shape from Motion, focus change imaging Shape from Defocus, stereovision technique Shape from Stereo, and surface shadowing imaging Shape from Shading. Active optical digitizing techniques use the reflection of light and laser beams emitted from the actual source to compute the surface shape. These techniques include Light Detection and Ranging (LiDAR), Time of Flight (ToF)  
Figure 2: Representation of reverse engineering techniques. calculations, Moire effect-based techniques, projection of structured light onto a surface and triangulation based techniques. The process of 3D surface digitization that eliminates the need for external references and repositioning of the technology relative to the object is challenging because it requires specialized equipment and techniques.