Model reconstruction from points scanned on existing physical objects is much important in a variety of situations such as reverse engineering for mechanical products, computer vision and recovery of biological shapes...Model reconstruction from points scanned on existing physical objects is much important in a variety of situations such as reverse engineering for mechanical products, computer vision and recovery of biological shapes from two dimensional contours. With the development of measuring equipment, cloud points that contain more details of the object can be obtained conveniently. On the other hand, large quantity of sampled points brings difficulties to model reconstruction method. This paper first presents an algorithm to automatically reduce the number of cloud points under given tolerance. Triangle mesh surface from the simplified data set is reconstructed by the marching cubes algorithm. For various reasons, reconstructed mesh usually contains unwanted holes. An approach to create new triangles is proposed with optimized shape for covering the unexpected holes in triangle meshes. After hole filling, watertight triangle mesh can be directly output in STL format, which is widely used in rapid prototype manufacturing. Practical examples are included to demonstrate the method.展开更多
Submerged caves and marine lakes are two iconic and common ecosystems in Ha Long-Cat Ba area. However, their biological characteristics are poorly known since very limited studies have been conducted, The aim of this ...Submerged caves and marine lakes are two iconic and common ecosystems in Ha Long-Cat Ba area. However, their biological characteristics are poorly known since very limited studies have been conducted, The aim of this study was to investigate biodiversity in these ecosystems. Three submerged caves （Hang Sang, Hang Toi and Qua Bang） and three marine lakes （Dau Be, Ang Du and Qua Bang） were chosen for study. The results showed that organism communities in submerged caves were abundant with over 142 species found. The popular groups comprised sponge and soft coral which were distributed along the length of the caves. Several species with high economic value were widespread in the caves, including stone crab Myomenippe hardwickii, flower crab Portunus pelagicus, cone snails Trochus pyramis, shoemaker spinefoot Siganus sutor, snapper Lutjanus russellii. Species that permanently live in caves were not detected. In the lakes where water is well exchanged to the sea, coral reefs were found and they usually formed a narrow band around the lakes. Sandy beaches were often observed around the lakes at the depths of 0.5-2 m, containing specialty species as clam （Sanguinolaria diphos）, snout otter clam （Lutraria rhychaena）, sea cucumbers with high density （in Dau Be, Qua Bang）. There was no coral reef in the enclosed lake （Ang Du） because of low salinity.展开更多
文摘Model reconstruction from points scanned on existing physical objects is much important in a variety of situations such as reverse engineering for mechanical products, computer vision and recovery of biological shapes from two dimensional contours. With the development of measuring equipment, cloud points that contain more details of the object can be obtained conveniently. On the other hand, large quantity of sampled points brings difficulties to model reconstruction method. This paper first presents an algorithm to automatically reduce the number of cloud points under given tolerance. Triangle mesh surface from the simplified data set is reconstructed by the marching cubes algorithm. For various reasons, reconstructed mesh usually contains unwanted holes. An approach to create new triangles is proposed with optimized shape for covering the unexpected holes in triangle meshes. After hole filling, watertight triangle mesh can be directly output in STL format, which is widely used in rapid prototype manufacturing. Practical examples are included to demonstrate the method.
文摘Submerged caves and marine lakes are two iconic and common ecosystems in Ha Long-Cat Ba area. However, their biological characteristics are poorly known since very limited studies have been conducted, The aim of this study was to investigate biodiversity in these ecosystems. Three submerged caves （Hang Sang, Hang Toi and Qua Bang） and three marine lakes （Dau Be, Ang Du and Qua Bang） were chosen for study. The results showed that organism communities in submerged caves were abundant with over 142 species found. The popular groups comprised sponge and soft coral which were distributed along the length of the caves. Several species with high economic value were widespread in the caves, including stone crab Myomenippe hardwickii, flower crab Portunus pelagicus, cone snails Trochus pyramis, shoemaker spinefoot Siganus sutor, snapper Lutjanus russellii. Species that permanently live in caves were not detected. In the lakes where water is well exchanged to the sea, coral reefs were found and they usually formed a narrow band around the lakes. Sandy beaches were often observed around the lakes at the depths of 0.5-2 m, containing specialty species as clam （Sanguinolaria diphos）, snout otter clam （Lutraria rhychaena）, sea cucumbers with high density （in Dau Be, Qua Bang）. There was no coral reef in the enclosed lake （Ang Du） because of low salinity.
