• 융복합기술연구소 논문집
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• 제10권1호
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• pp.7-12
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• 2020

We describe a efficient surface reconstruction method that reconstructs a 3D manifold polygonal mesh approximately passing through a set of 3D oriented points. Our algorithm includes 3D convex hull, octree data structure, signed distance function (SDF), and marching cubes. The 3D convex hull provides us with a fast computation of SDF, octree structure allows us to compute a minimal distance for SDF, and marching cubes lead to iso-surface generation with SDF. Our approach gives us flexibility in the choice of the resolution of the reconstructed surface, and it also enables to use on low-level PCs with minimal peak memory usage. Experimenting with publicly available scan data shows that we can reconstruct a polygonal mesh from point cloud of sizes varying from 10,000 ~ 1,000,000 in about 1~60 seconds.

• 제어로봇시스템학회논문지
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• 제21권5호
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• pp.459-464
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• 2015

An on-line quality control of hot steel products is one of the important issues in the steel industry because of cost minimization. In recent years, relative depth information of surface defects is increasingly required for strict quality control. In this paper, a 3D shape reconstruction scheme for defects on a hot steel surface based on a multi-spectral photometric stereo method is proposed. After simultaneously illuminating a hot steel surface by using vertical/horizontal linearly polarized lights of green and blue light sources, the corresponding 4 images are obtained. The photometric stereo method is then applied with the aid of a GPU (Graphic Processing Unit) to reconstruct the shape of the target surface based on these images. The proposed scheme was validated through experiments.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1695-1700
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• 2005

In this paper, we propose an optimal thresholding method for the voxel coloring in the reconstruction of a 3D shape. Our purposed method is a new approach to resolve the trade-off error of the threshold value on determining the photo-consistency in the conventional method. Optimal thresholding value is decided to compare the surface voxel of photo-consistency with inside voxel on the optic ray of the center camera. As iterating the process of the voxels, the threshold value is approached to the optimal value for the individual surface voxel. And also, graph cut method is reduced to the surface noise on eliminating neighboring voxel. To verify the proposed algorithm, we simulated in the virtual and real environment. It is advantaged to speed up and accuracy of a 3D face reconstruction by applying the methods of optimal threshold and graph cut as compare with conventional algorithms.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권6호
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• pp.3121-3142
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• 2017

We present a method for 3D shape reconstruction of inextensible deformable surfaces from a single image. The key of our approach is to represent the surface as a 3D triangulated mesh and formulate the reconstruction problem as a sequence of Linear Programming (LP) problems. The LP problem consists of data constraints which are 3D-to-2D keypoint correspondences and shape constraints which are designed to retain original lengths of mesh edges. We use a closed-form method to generate an initial structure, then refine this structure by solving the LP problem iteratively. Compared with previous methods, ours neither involves smoothness constraints nor temporal consistency, which enables us to recover shapes of surfaces with various deformations from a single image. The robustness and accuracy of our approach are evaluated quantitatively on synthetic data and qualitatively on real data.

• 한국정보과학회논문지:시스템및이론
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• 제34권1호
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• pp.28-37
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• 2007

단층촬영 영상으로부터 임의의 등밀도 표면을 재구성하기 위한 새로운 방법을 제안하였다. 제안된 방법은 이 분야의 가장 대표적인 알고리즘인 마칭큐브에서와는 달리 단층영상에서 직접 등밀도 표면을 생성하지 않고 등밀도점을 먼저 추출하며, 셀경계 알고리즘을 이용하여 구한 초기메쉬의 각 정점들을 이들 등밀도점 방향으로 표면축소포장(Shrink-wrapping)하는 과정을 반복적으로 적용하여 등밀도 표면을 추출한다. 이렇게 함으로써 마칭큐브에서 나타나는 크랙이나 표면결정의 모호성이 발생하지 않고 안정적인 표면을 재구성 할 수 있다. 또한, 마칭큐브에서 O(1)-인접한 등밀도점만을 사용할 수 있는데 비해, 제안된 방법은 O(2) 및 O(3)-인접한 등밀도점을 표면재구성에 활용할 수 있게 함으로써 이론적으로 마칭큐브 알고리즘보다 더 정밀한 표면을 추출할 수 있도록 하였다. 실험을 통해 제안된 표면 재구성 알고리즘이 단층영상에서부터 등밀도면을 재구성하는데 매우 안정적이고 정확하며 효과적임을 확인할 수 있었다.

• 대한전자공학회논문지SP
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• 제41권4호
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• pp.69-74
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• 2004

본 논문에서는 프로젝션 프로파일(PP： Projection Profile) 과 컬러공간변환(CST： Color Space Transform)을 이용하여 라인스캔 카메라(Line-Scan Camera) 영상을 재구성함으로써 LCD 표면의 결함검출 성능을 높이는 알고리즘을 제안하였다. 제안된 알고리즘은 결함을 포함한 RGB 영역 분할, 대표값 추적시스템을 이용한 대표값 추출, 그리고 컬러공간변환을 이용한 Y영상 재구성 방법들로 구성되어 있다. 실험을 통하여 제안한 방법으로 재구성된 영상의 결함검출 성능이 영역카메라(Aerial Camera)의 결함검출 성능보다 우수함을 보였다.

• 대한물리의학회지
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• 제3권1호
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• pp.11-20
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• 2008

Purpose : This study was to comparison of EMG of an stable exercise group and unstable exercise group on patients who have had anterior cruciate ligament reconstruction(ACL reconstruction). Methods : The subjects of the study were patients who had no less than 4 weeks after ACL reconstruction and could stand on one leg, and they divided into a control group with 9 patients doing closed kinetic chain exercises on the stable floor and an experimental group with 10 patients doing closed kinetic chain exercises on the unstable floor and in order to compare degrees of the muscle activity of the thigh extensor and flexor was tested each before the exercise, in 3 weeks and 6 weeks after doing exercises by using surface electromyography (Surface EMG). The patients made 3 sets of exercises (10 times per set), each of which consisted of exercises using elastic bands and the squat. Results : There was statistic significance about the vastus medialis muscle. Conclusion : It is thought that the closed-chain exercise could be an exercise program through which patients could enhance the muscle activity of the vastus medialis muscle optionally among the quadriceps muscle and the hamstring muscles which should weaken after ACL reconstruction.

• Journal of Construction Engineering and Project Management
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• 제2권3호
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• pp.1-7
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• 2012

The reconstruction of surfaces from unorganized point clouds can provide very useful information for construction managers. Although point clouds are generally created using 3D scanners, they can also be generated via the structure-from-motion technique using a sequence of images. Here we report a novel surface reconstruction technique for modeling and quantifying earthworks that can be used for preliminary planning, project updates and estimating of earthwork quantities, as well as embedded planning systems in construction equipment. The application of structure-from-motion techniques in earth works is examined and its advantages and limitations identified. Data from 23 earthwork excavation construction sites were collected and analyzed. 3D surface reconstructions during the construction phase were compared to the original land form. Similar experiments were conducted with piles of earth and the results analyzed to determine appropriate ranges of use for structure-from-motion surface reconstructions in earthwork applications. The technique was found to be most suited to pile of materials with volumes less than 2000 m3. Piles up to 10 m in height and with base areas up to $300m^2$ were also successfully reconstructed. These results should be of interest to contractors seeking to utilize new technology to optimize operational efficiency.

• International Journal of CAD/CAM
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• 제7권1호
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• pp.103-112
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• 2007

This paper presents a practical approach for surface reconstruction from unoriented point clouds. Instead of estimating local surface orientation, we first generate a set of depth images from the input point clouds, and a coarse mesh is then generated based on them by space carving techniques. The resultant mesh is progressively refined by local mesh refinement and optimization according to surface distance measure. A manifold mesh approximating the input points within an given tolerance is finally obtained. Our approach is easy to implement, but has the ability to outputs high quality meshes in different resolutions. We show that the proposed approach is not sensitive to several types of data disfigurement and is able to reconstruct models robustly from variance input data.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제23권1호
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• pp.31-38
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• 2019

We present an explicit numerical algorithm for surface reconstruction from unorganized points using the Gaussian filter. We construct a surface from unorganized points and solve the modified heat equation coupled with a fidelity term which keeps the given points. We apply the operator splitting method. First, instead of solving the diffusion term, we use the Gaussian filter which has the effect of diffusion. Next, we solve the fidelity term by using the fully implicit scheme. To investigate the proposed algorithm, we perform computational experiments and observe good results.