• International Journal of Naval Architecture and Ocean Engineering
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• 제4권3호
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• pp.228-240
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• 2012

Morphing is a geometric interpolation technique that is often used by the animation industry to transform one form into another seemingly seamlessly. It does this by producing a large number of 'intermediate' forms between the two 'extreme' or 'parent' forms. It has already been shown that morphing technique can be a powerful tool for form design and as such can be a useful addition to the armoury of product designers. Morphing procedure itself is simple and consists of straightforward linear interpolation. However, establishing the correspondence between vertices of the parent models is one of the most difficult and important tasks during a morphing process. This paper discusses the mesh-merging method employed for this process as against the already established mesh-regularising method. It has been found that the merging method minimises the need for manual manipulation, allowing automation to a large extent.

• International Journal of Contents
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• 제3권2호
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• pp.25-29
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• 2007

In this paper, we discuss the mesh segmentation problem which divides a given 3D mesh into several disjoint sets. To solve the problem, we propose a greedy method based on the merging priority metric defined for representing the geometric properties of meaningful parts. The proposed priority metric is a weighted function using five geometric parameters, those are, a distribution of Gaussian map, boundary path concavity, boundary path length, cardinality, and segmentation resolution. In special, we can control by setting up the weight values of the proposed geometric parameters to obtain visually better mesh segmentation. Finally, we carry out an experiment on several 3D mesh models using the proposed methods and visualize the results.

• 정보과학회 논문지
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• 제43권4호
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• pp.419-429
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• 2016

최근 관상동맥 영역화 결과로부터 삼차원 표면 모델을 생성함으로써 혈관 구조적 정보의 렌더링 효율성의 증대뿐만 아니라 전산유체역학를 이용한 혈류 역학 시뮬레이션을 통해 혈류분획예비력과 같은 생리적 정보들을 획득하는 연구들이 활발히 진행되고 있다. 본 논문에서는 혈관 영역화 과정에서 획득한 혈관 구조 정보를 입력 데이터로 사용하여 관상동맥의 삼차원 삼각 표면 메쉬 모델을 생성하는 방법을 제안한다. 관상동맥 영역화 결과로부터 삼각형 표면 메쉬 모델을 만드는 방법으로는 Marching cube 알고리즘에 기반한 방법들이 있지만 이산적인 영상 공간에서 수행되는 알고리즘으로 가늘고 다양한 굴곡을 갖는 혈관 경계를 표현하기 힘들다. 제안된 방법은 관상동맥 영역화 과정에서 추정한 혈관 중심좌표와 법선 벡터 그리고 직경 정보를 이용하여 기존 방법들보다 정교하게 단일 혈관 가닥들에 대한 삼각 표면 메쉬들을 생성하고 분기가 일어나 중첩되는 메쉬들은 메쉬 병합 기법을 사용하여 처리함으로써 통합된 관상동맥 메쉬를 생성한다.

• 한국콘텐츠학회논문지
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• 제7권6호
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• pp.52-59
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• 2007

이 논문은 삼차원 메쉬의 의미있는 조각의 기하적 속성을 나타내기 위하여 정의한 병합우선순위메트릭에 기반한 사용자 의도 메쉬분할의 그리디 방법을 제시한다. 우선순위메트릭은 가우시안사상의 분포, 경계경로의 오목성, 경계경로의 길이, 면의 개수, 분할해상도의 5 가지 기하적 매개변수로 구성된 가중치 함수이다. 이러한 방식은 구도의 변경 없이 다른 기하적 매개변수를 정의하고 추가함으로써 확장될 수 있다. 실험 결과, 분할된 조각의 모양은 기하적 매개변수의 가중치를 부여함으로써 사용자 의도대로 조절될 수 있음을 보여준다.

• 대한전자공학회논문지SP
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• 제40권6호
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• pp.132-140
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• 2003

본 논문에서는 삼차원 모델을 효율적으로 전송하기 위해, 삼차원 메쉬 모델을 계층적으로 표현하고 보는 사람의 시점에 따라 메쉬 모델의 해상도를 다르게 하여 전송하는 방법을 제안한다. 제안한 방법은 점진적 메쉬 전송과 순차적 메쉬 전송이 결합된 형태로 보는 사람의 현재 시점을 고려하여 삼차원 모델을 전송하는 것이다. 보는 사람의 시각 위치에 따라 전송할 때, 보이지 않는 부분보다 보이는 부분을 먼저 전송하여 제한된 전송대역 안에서 삼차원 모델의 품질을 최적화 할 수 있다. 먼저 주어진 삼차원 메쉬 모델을 계층적으로 메쉬 분할하고 최하위 레벨의 분할메쉬에 대해 다중계층을 구성한다. 메쉬분할을 위한 시작꼭지점은 K-means 알고리즘을 사용하여 선택하기 때문에, 메쉬분할 과정에서 균등한 분할메쉬를 얻을 수 있다. 보는 사람의 시점에 따라 최하위 레벨의 각 분할메쉬에 대해서 해상도를 계산한 후, 병합과 분리과정을 통해 삼차원 메쉬 모델을 전송한다. 분할메쉬 병합과정은 삼차원 메쉬의 정적시각 전송에 이용피고, 메쉬분할로 생기는 공통 경계 정보를 줄일 수 있다. 분할메쉬 분리과정은 삼차원 메쉬의 동적시각 전송에 이용되고, 보는 사람의 시점에 따라 새롭게 보이는 분할메쉬에 대해 추가적인 정보를 유동적으로 전송한다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.116-120
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• 2009

A two-dimensional unsteady inviscid flow solver has been developed for the simulation of complex geometric configurations on adaptive Cartesian meshes. Embedded condition was used for boundary condition and a predictor-corrector explicit time marching scheme was used for time-accurate numerical simulation. The Cartesian mesh generator, which was previously developed for steady problem, was used grid generation for unsteady flow. The solver was based on ALE formulation for body motion. For diminishing the effects of cut-cells, the cell merging method was used. Using cell merging method, it was eliminated the CFL constraints. The conservation problem, which is caused cell-type variation around region swept by solid boundary, was also solved using cell merging method. The results are presented for 2D circular cylinder and missile launching problem.

• 대한기계학회논문집A
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• 제31권7호
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• pp.739-746
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• 2007

Recently, models in STL files are widely used in reverse engineering processes, CAD systems and analysis systems. However the models have poor geometric quality and include only triangles, so the models are not suitable for the finite element analysis. This paper presents a general method that generates finite element mesh from STL file models. Given triangular meshes, the method estimates triangles and makes clusters which consist of triangles. The clusters are merged by some geometric indices. After merging clusters, the method applies plane meshing algorithm, based on domain decomposition method, to each cluster and then the result plane mesh is projected into the original triangular set. Because the algorithm uses general methods to generate plane mesh, we can obtain both tri and quad meshes unlike previous researches. Some mechanical part models are used to show the validity of the proposed method.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1564-1569
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• 2007

This study concerns an advanced NURBS surface reconstruction method, which is based on the NURBS surface model fitting to the unstructured point cloud measured from an arbitrary complex shape. The concept of generating a simple triangular mesh model was introduced to generate a quadrilateral mesh model well-representing the topological characteristics of point cloud. The NURBS surface reconstruction processes required the use of the various methodologies such as QEM algorithm, merging scheme of pair-wise triangular mesh, creation algorithm of $G^1$ continuous tensor product NURBS surface patch, and so on. The effectiveness and reliability of the proposed NURBS surface reconstruction method were validated through the simulation results for the geometrically and topologically complex shapes.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.366-371
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• 2007

In many CAD systems, NURBS has been employed to construct exact geometries. Recently, NURBS finite element analysis methods were proposed by some authors for convenient connection between CAD and finite element analysis. Additional advantages of NURBS FEA, such as exact geometry and no mesh generation, are obtained. However, NURBS is inefficient in local refinement and merging patches. For refinement of local region in interest, additional control points should be inserted into the entire row or column which contains the local region. There is another inefficiency of NURBS during merging patches into a large structure due to propagation of control points. In order to overcome these inefficiencies of NURBS, T-spline was proposed by Sederberg. In this work, T-spline based finite element method is proposed for efficient local refinement and merging patches. At first, accuracy and efficiency of NURBS FEA is verified and efficiency of T-spline FEA is verified by comparing with NURBS FEA.

• 한국멀티미디어학회논문지
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• 제20권2호
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• pp.179-187
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• 2017

The fourth industrial revolution is a phenomenon where productivity is improved in each field by the convergence of IT technology and existing industries. In the dental treatment process, prosthetic treatment time is drastically shortened through AI and expert software. Oral imaging, prosthesis design, and prosthesis manufacturing are performed continuously, so the treatment can be completed in a few hours. In this paper, we introduce the research trend of multimedia technology in the prosthetic process. We also propose a new method for accelerating the fusion of surface data during the optical impression. Proposed method enables high-speed optical impression and accelerates the overall automated production process of dental prosthesis.