Comparative Analysis Between the Main 3D Scanning Techniques: Photogrammetry, Terrestrial Laser Scanner, and Structured Light Scanner in Religious Imagery: The Case of The Holy Christ of the Blood

In recent years, three-dimensional (3D) scanning has become the main tool for recording, documenting, and preserving cultural heritage in the long term. It has become the “document” most in demand today by historians, curators, and art restorers to carry out their work based on a “digital twin,” that is, a totally reliable and accurate model of the object in question. Thanks to 3D scanning, we can preserve reliable models in digital format of the real state of our heritage, some of which are currently destroyed. The first step is to digitize our heritage with the highest possible quality and precision. To do this, it will be necessary to identify the most appropriate technique. In this article, we will show some of the main digitization techniques currently used in sculpture heritage and the workflows associated with them to obtain high-quality models. Finally, a complete comparative analysis will be made to show their main advantages and disadvantages.

3D Scanning/Printing: A Technological Stride in Sculpture

The creation of innovative tools, objects and artifacts that introduce abstract ideas in the real world is a necessary step for the evolution process and characterize the creative capacity of civilization. Sculpture is based on the available technology for its creation process and is strongly related to the level of technological sophistication of each era. This paper analyzes the evolution of basic sculpture techniques (carving, lost-wax casting and 3D scanning/printing), and their importance as a culture footprint. It also presents and evaluates the added creative capacities of each technological step and the different methods of 3D scanning/printing concerning sculpture. It is also an attempt to define the term “material poetics”, which is connected to sculpture artifacts. We conclude that 3D scanning/printing is an important sign of civilization, although artifacts lose a part of material poetics with additive manufacturing. Subsequently, there are various causes of the destruction of sculptures, leaving a hole in the history of art. Finally, this paper showcases the importance of 3D scanning/printing in salvaging cultural heritage, as it has radically altered the way we “backup” objects.

Choosing the Optimal Tissue Expander Size: A Single Center Randomized Clinical Trial on Chinese Microtia Patients’ Normal Ears Using 3D Scanning

The tissue expansion technique is the most suitable procedure for Chinese patients with microtia. However, it is difficult to determine whether the expanded flap is sufficient, and there are no clear or objective guidelines for determining the volume of the expander for different sizes of auricles. One hundred patients with unilateral microtia who visited our department in 2021 were randomly selected for auricular data collection using 3D scanning. The auricle length, width, projection, perimeter, and surface area were measured. Eight different volumes of expanders underwent CT and the surface areas of these expanders were measured. The surface areas of the auricles and expanders were compared and the correlation between them was explored. The average auricle parameters were calculated. The scatter plot showed a linear relationship between auricle length and auricle surface area (R2 = 0.9913), which demonstrated that the auricle area was approximately equal to the auricle length multiplied by 76.921. Additionally, the surface area of the expanders was measured and made into a table for selection against the surface area of the auricles. Using our equation, the auricle surface could be estimated by simply measuring the non-defective auricle length; therefore, the suitable volume of the expander could be determined.

Artificial intelligence technologies for more flexible recommendation in uniforms

PurposeThis research aims to collect human body variables via 2D images captured by digital cameras. Based on those human variables, the forecast and recommendation of the Digital Camouflage Uniforms (DCU) for Taiwan's military personnel are made.Design/methodology/approachA total of 375 subjects are recruited (male: 253; female: 122). In this study, OpenPose converts the photographed 2D images into four body variables, which are compared with those of a tape measure and 3D scanning simultaneously. Then, the recommendation model of the DCU is built by the decision tree. Meanwhile, the Euclidean distance of each size of the DCU in the manufacturing specification is calculated as the best three recommendations.FindingsThe recommended size established by the decision tree is only 0.62 and 0.63. However, for the recommendation result of the best three options, the DCU Fitting Score can be as high as 0.8 or more. The results of OpenPose and 3D scanning have the highest correlation coefficient even though the method of measuring body size is different. This result confirms that OpenPose has significant measurement validity. That is, inexpensive equipment can be used to obtain reasonable results.Originality/valueIn general, the method proposed in this study is suitable for applications in e-commerce and the apparel industry in a long-distance, non-contact and non-pre-labeled manner when the world is facing Covid-19. In particular, it can reduce the measurement troubles of ordinary users when purchasing clothing online.

An Approach for Direct Offline Programming of High Precision Assembly Tasks on 3D Scans Using Tactile Control and Automatic Program Adaption

This contribution defines a methodology for the direct offline programming of robotic high-precision assembly tasks without the need for real-world teach-in, even for less-accurate lightweight robots. Using 3D scanning technologies, the relevant geometrical relations of the offline programming environment are adjusted to the real application. To bridge remaining accuracy gaps, tactile insertion algorithms are provided. As repetitive inaccuracy compensation through tactile search is considered wasteful, a method to automatically adapt the robot program to continuously increase precision over time, taking into account multiple influence sets is derived. The presented methodology is validated on a real-world use case from electronics production.

Image binarization method for markers tracking in extreme light conditions

Image binarization is one of the fundamental methods in image processing and it is mainly used as a preprocessing for other methods in image processing. We present an image binarization method with the primary purpose to find markers such as those used in mobile 3D scanning systems. Handling a mobile 3D scanning system often includes bad conditions such as light reflection and non-uniform illumination. As the basic part of the scanning process, the proposed binarization method successfully overcomes the above problems and does it successfully. Due to the trend of increasing image size and real-time image processing we were able to achieve the required small algorithmic complexity. The paper outlines a comparison with several other methods with a focus on objects with markers including the calibration system plane of the 3D scanning system. Although it is obvious that no binarization algorithm is best for all types of images, we also give the results of the proposed method applied to historical documents.

A COMPARISON OF LASER AND STRUCTURED LIGHT SCANNING TECHNOLOGIES FOR ARCHAEOLOGICAL APPLICATIONS

Reverse engineering and in particular three-dimensional digitization have become an essential part of the documentation of archaeological findings. 3D scanning produces a high-precision digital reference document. The factors that influence the quality of the 3D scanned data are the scanned object’s surface colour, its glossiness and geometry, and the ambient light during the scanning process. However, the actual equipment and scanning technologies are of primary importance. The current paper presents a qualitative and quantitative comparison between two 3D scanning devices of different technologies; structured light 3D scanning and laser 3D scanning. The benchmark for this comparison is an ancient Roman vase from the city of Thessaloniki, Greece. The object was scanned with every possible setting on each scanner, but only one configuration of settings on each device was selected for the final comparison. The main criterion for the final selection of the two 3D models acquired with the use of the two technologies was the proximity in the number of points and polygons produced for digitally restoring the ancient vase in the best possible way. The results indicate important differences regarding the accuracy of the final digital model. The laser technology produced better accuracy but with a significant cost in scanning time and model data size. On the other hand, the structured light technology achieved the optimal combination of scanning quality and accuracy, along with reduced acquisition time of scan data.