HOLOGRAPHIC VISUALIZATION AND MANAGEMENT OF BIG POINT CLOUD

The work aims to present and validate the workflow from the 3D survey to the visualization of cultural heritage objects using the innovative Euclideon Hologram Table©. Three case studies surveyed with three different systems and at three different scales have been selected: Santa Maria delle Grazie in Milan (terrestrial laser scanner for an architecturalscale), the village of Ghesc in the Ossola valley (UAV survey for an environmental scale) and the cuneiform clay tablet number 727 (structured light system for a detailscale). The whole process of transforming the 3D point/mesh model to hologram was verified, analysing the file formats, technical performance and specifications, file dimensions manageable, and details viewable. The first test shows great potentiality, becausethe hologram exploring is impressively fluid even when zooming to view a higher detail level, despite the high number of points/polygons. The power and performance of the point cloud 3D rendering engine result impressive. Nonetheless,different aspects need further research, from point cloud visualization quality to enhancing 3D model interaction.

LANDSCAPE ANALYSIS TECHNIQUES APPLIED TO A BUDDHIST CARVED ROCK SCULPTURE

The Swat valley (Pakistan) has always been considered an important center of Gandhara art. Due to the unfavourable conditions, this artistic phenomenon has long been almost ignored or underestimated, but its documentation is essential for study the symbolism of the figures, their spatial organization, their stylistic variation and their conservative state. The methodology proposed in this project starts form the 3D acquisition with a structured light system in order to obtain a 3D high resolution model of Buddhist carved rock sculpture. From the 3D geometry, The Digital Elevation Model is produced. This DEM is the starting points for the surface analysis using Remote Sensing approaches for classify landforms using pattern recognition. The surface is considered as a landscape, where carved are valleys bordered by slopes and crests. Hillshading, slope analysis and geomorphons are used in order to highlight the surface feature, to “read” all the details not visible due to the bad condition and to map surface state of conservation.

A Framework in Calibration Process for Line Structured Light System Using Image Analysis

Line structured light systems have been widely applied in the measurement of various fields. Calibration has been a hot research topic as a vitally important process of the line structured light system. The accurate calibration directly affects the measurement result of the line structured light system. However, the external environment factors, such as uneven illumination and uncertain light stripe width, can easily lead to an inaccurate extraction of light stripe center, which will affect the accuracy of the calibration. An image analysis-based framework in the calibration process was proposed for the line structure light system in this paper. A three-dimensional (3D) vision model of line structure light system was constructed. An image filtering model was established to equalize the uneven illumination of light stripe image. After segmenting the stripe image, an adaptive window was developed, and the width of the light stripe was estimated by sliding the window over the light stripe image. The light stripe center was calculated using the gray centroid method. The light plane was fitted based on the calibration points coordinates acquired by the camera system. In the measurement experiment of standard gauge block width, the maximum and minimum average deviations of 0.021 pixels and 0.008 pixels and the maximum and minimum absolute deviations of 0.023 pixels and 0.009 pixels could be obtained by using the proposed method, which implies the accuracy of the proposed method.

In-situ Monitoring of Direct Energy Deposition via Structured Light System and its Application in Remanufacturing Industry

The Direct Energy Deposition (DED) process utilizes laser energy to melt metal powders and deposit them on the substrate layer to manufacture complex metal parts. This study was applied as a remanufacturing and repair process to fix used parts, which reduced unnecessary waste in the manufacturing industry. However, there could be defects generated during the repair, such as porosity or bumpy morphological defects. Traditionally the operator would use a design of experiment (DOE) or simulation method to understand the printing parameters’ influence on the printed part. There are several influential factors: laser power, scanning speed, powder feeding rate, and standoff distance. Each DED machine has a different setup in practice, which results in some uncertainties for the printing results. For example, the nozzle diameter and laser type could be varied in different DED machines. Thus, it was hypothesized that a repair could be more effective if the printing process could be monitored in real-time. In this study, a structured light system (SLS) was used to capture the printing process’s layer-wise information. The SLS system is capable of performing 3D surface scanning with a high-resolution of 10 µm. To determine how much material needs to be deposited, given the initial scanning of the part and allowing the real-time observation of each layer’s information. Once a defect was found in-situ, the DED machine (hybrid machine) would change the tool and remove the flawed layer. After the repair, the nondestructive approach computed tomography (CT) was applied to examine its interior features. In this research, a DED machine using 316L stainless steel was used to perform the repairing process to demonstrate its effectiveness. The lab-built SLS system was used to capture each layer’s information, and CT data was provided for the quality evaluation. The novel manufacturing approach could improve the DED repair quality, reduce the repair time, and promote repair automation. In the future, it has a great potential to be used in the manufacturing industry to repair used parts and avoid the extra cost involved in buying a new part.