## 2 Literature Review
### 3D Reality Capture Approaches in Heritage  
This 3D reality capture technique in heritage preservation, utilizing 3D laser scanning and data processing, represents a revolutionary approach to documenting and conserving our cultural legacy. Three-dimensional laser scanning, a non-invasive and high-precision technology, allows for the rapid and accurate acquisition of detailed 3D point cloud data from heritage sites and artifacts [18]. These data serve as a foundation for the creation of comprehensive and lifelike 3D models, preserving the intricate details of historical structures and objects. Advanced data processing techniques, including registration, filtering, and mesh generation, play a pivotal role in refining the raw point cloud data into precise and visually appealing reconstructions [19]. By harnessing the benefits of 3D reality capture, heritage preservation efforts can maintain the integrity of sites, minimize physical intrusion, enhance documentation accuracy, and facilitate research and virtual visualization, ensuring our cultural heritage is safeguarded for future generations. Although some challenges exist, such as equipment cost and data volume, continuous technological advancements and research will undoubtedly propel the field of 3D reality capture further, revolutionizing the way we approach heritage conservation and research [20]. The 3D reality capture approaches can be categorized into two main methods. The first method is 3D laser scanning, which entails the utilization of a 3D laser scanner to capture intricate 3D data of the building's surface geometry, including its roof, walls, windows, and other features. This process involves emitting a laser beam from the scanner, which reflects off the surfaces of the building. The scanner's sensor then records the reflection and measures the distance from the scanner to each point on the building's surface [14]. Moreover, terrestrial laser scanning is an automated measurement method used to determine the 3D surface coordinates of a selected object. The output data from the laser scan is displayed as a point cloud, with each point comprising x, y, and z coordinates indicating the scanned surface. Currently, there are several laser scanning systems offered on the engineering market, each employing one of three different scanner methods: time-of-flight, triangulation, and phase comparison [21]. These methods can be advantageous for metric heritage studies. The variation between these scanner systems lies in how they compute 3D coordinate measurements. For instance, in the case of the triangulation type, the scanner employs laser beam points on the object's surface, which are captured using one or more cameras [22]. The second approach is photogrammetry, which is a powerful 3D reality capture approach that has found numerous applications in the heritage and cultural preservation sector. It involves the use of photographs or images to create accurate and realistic 3D models of real-world objects or environments. In the context of heritage, photogrammetry is particularly valuable for documenting and preserving historical sites, artifacts, and buildings [20]. Furthermore, photogrammetry is used to capture detailed 3D models of archaeological sites, allowing researchers to preserve the site's condition at a specific point in time. These models can be used for analysis, virtual reconstructions, and dissemination of information to the public. Moreover, it can be noted that historic buildings and structures are at risk of deterioration over time. Photogrammetry can be used to create accurate 3D models of these buildings, serving as a record of their original state, and supporting restoration efforts [23]. Additionally, photogrammetry-generated 3D models allow users to experience heritage sites or artifacts in immersive VR or AR environments. This enhances educational opportunities and visitor engagement [24]. It is important to note that photogrammetry does have certain requirements for optimal results.