1.8 Designing, Digital Imaging, and Modelling
Nowadays, technological advancements made 3D printing easier and more accessible. 3D models can be directly downloaded in STL format from online webpages such as Thingiverse, Cults, Pinshape, Turbosquid, Youmagine, etc. (Table 1.2). These web pages allow the users to download the 3D models instantly either for free or paid. Otherwise, 3D scanners are employed for scanning of real‐time objects and the scanned object in STL format was processed using slicing software.
1.8.1 Image Acquisition, Processing, and Modelling
3D scanning is used for capturing the surface characteristics of a physical object using a 3D scanner. The output of scanning is the generation of a 3D model file that can be edited using designing software or can be taken for 3D printing directly. The objects to be scanned can be a real‐time object, natural scenarios (place/surroundings), or a person. The information obtained during scanning can be extracted and reproduced using a process called reverse engineering (Guo et al. 2019). Considering the affordability, portability, and versatility, reverse engineering employs two types of 3D scanning equipment namely contact and non‐contact scanners (Table 1.3). Contact scanners are point‐based systems that employ a probe to touch the object to be scanned. Both data collection and designing can be done simultaneously using a portable coordinate measuring machine (CMM) (Martinez‐Pellitero et al. 2018). On the other hand, non‐contact 3D scanners use an array of laser/ light beams to extract the surface information of the object. These types of scanners project either a laser beam or structured light on the object that aids in capturing the surface data. A web camera which on integration with software aids in transferring the reflected beam into the 3D model data for printing (Wei et al. 2019). Based on the mode of applications, 3D scanners are categorized as desktop scanners (EinScan, Solutionix 500) and handheld scanners (Sense, EinScan Pro 2X, Structure sensor). Most of the scanners are adaptable with computers while some other advanced versions employ the iPad to transfer the 3D model.
Another type of scanning technique is photogrammetry in which 3D models are obtained from 2D photographs by integrating computer vision and computational algorithms. Photogrammetry is based on analyzing several static points in the 2D photographs taken from different views so that it would detect the pixel corresponding to actual physical objects (Peña‐Villasenin et al. 2020). Image processing depends on the focal length of the camera and the distortion of the lens. The major advantage of photogrammetry is its acquisition speed and model precision. However, it requires more processing time to run the algorithms that limit its applications.
Table 1.2 List of online sources for downloading 3D models.