• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.784-787
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• 2002

The NURBS surfaces are widely employed for exchanging geometric models between different CAD/CAE systems. However if the input NURBS surfaces are poorly parameterized, most surface meshing algorithms may fail or the constructed meshes can be ill-conditioned. In this paper presents a new method is presented that can generate well conditioned meshes even on poorly parameterized NURBS surfaces by regenerating NURBS surfaces. To begin with, adequate Points are sample on original poorly parameterized surfaces and new surfaces are created by interpolating these points. And then. mesh generation is performed on new surfaces. With this method, models with poorly parameterized NURBS surfaces can be meshed successfully.

• 한국멀티미디어학회논문지
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• 제6권7호
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• pp.1302-1311
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• 2003

본 논문에서는 삼각 메쉬에 관한 보다 안정되고 직관적인 새로운 다중해상도 메쉬 편집 기술을 제안한다. 본 논문의 기본 아이디어는 3차원 메쉬 상에서 편집 영역을 선택하여 2차원 영역으로 임베딩을 하는 과정과 사용자에 의해서 정의되는 편집 정보를 보간하는 곡면을 생성하는 과정으로 이루어지며, 이를 통해 편집 영역 안에 있는 다른 꼭지점의 변위 정보를 곡면 함수값으로부터 생성한다. 본 논문에서 사용되는 임베딩 방법은 확장 볼록 조합 매개변수화 방법으로서 임베딩된 2차원 메쉬의 삼각형들은 자기 교차를 하지 않으며 또한 볼록 조합 계수를 정의할 때 모양 유지 방법을 사용하기 때문에 3차원 삼각형의 모양을 제대로 유지할 수 있다. 또한 편집 결과의 영역을 조절할 수 있도록 하기 위하여 다단계 B-스플라인 곡면을 이용하여, 상호작용적이며 직관적이어서 보다 안정되고 효율적인 메쉬 편집 결과를 얻을 수 있다.

• 한국정밀공학회지
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• 제20권6호
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• pp.189-196
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• 2003

The NURBS surfaces are widely employed for exchanging geometric models between different CAD/CAE systems. However if the input NURBS surfaces are poorly parameterized, most surface meshing algorithms may fail or the constructed meshes can be ill-conditioned. In this paper presents a new method is presented that can generate well conditioned meshes even on poorly parameterized NURBS surfaces by regenerating NURBS surfaces. To begin with, adequate points are sampled on original poorly parameterized surfaces and new surfaces are created by interpolating these points. And then, mesh generation is performed on new surfaces. With this method, models with poorly parameterized NURBS surfaces can be meshed successfully.

• 한국CDE학회논문집
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• 제13권6호
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• pp.450-458
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• 2008

Recently, Cartesian grid approach has been popular to generate grid meshes for complex geometries in CFD (Computational Fluid Dynamics) because it is based on the non-body-fitted technique. This paper presents a method of an octree generation and boundary cell clipping using section curves for fast octree generation and elimination of redundant intersections between boundary cells and triangles from 3D triangular mesh. The proposed octree generation method uses 2D Scan-Converting line algorithm, and the clipping is done by parameterization of vertices from section curves. Experimental results provide octree generation time as well as Cut-cell clipping time of several models. The result shows that the proposed octree generation is fast and has linear relationship between grid generation time and the number of cut-cells.

• 한국컴퓨터그래픽스학회논문지
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• 제7권3호
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• pp.9-18
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• 2001

삼각 메쉬의 특징점을 찾는 것은 메쉬 편집, 메쉬 몰핑, 메쉬 압축, 메쉬 신호처리 등 여러 가지 응용 분야에서 중요하게 사용된다. 본 논문에서는 삼각 메쉬의 특징점을 찾기 위한 방법으로 기하학 스네이크를 제시하였다. 기하학 스네이크는 영상 스네이크를 확장한 것으로, 사용자가 초기 위치를 정하면 에너지 함수를 최소화함으로써 가까이에 있는 특징점을 찾는다. 기하학 스네이크는 항상 메쉬 표면 위에서만 이동하여야 하므로 메쉬를 매개 변수화하여 스네이크를 이차원 상에 매핑된 메쉬상에서 이동시켰다. 스네이크를 특징점으로 이동시키기 위한 외부 에너지는 메쉬 표면의 노말 변화를 이용하여 계산하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.216-221
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• 2008

Shape design optimization for linear elasticity problem is performed using isogeometric analysis method. In many design optimization problems for real engineering models, initial raw data usually comes from CAD modeler. Then designer should convert this CAD data into finite element mesh data because conventional design optimization tools are generally based on finite element analysis. During this conversion there is some numerical error due to a geometry approximation, which causes accuracy problems in not only response analysis but also design sensitivity analysis. As a remedy of this phenomenon, the isogeometric analysis method is one of the promising approaches of shape design optimization. The main idea of isogeometric analysis is that the basis functions used in analysis is exactly same as ones which represent the geometry, and this geometrically exact model can be used shape sensitivity analysis and design optimization as well. In shape design sensitivity point of view, precise shape sensitivity is very essential for gradient-based optimization. In conventional finite element based optimization, higher order information such as normal vector and curvature term is inaccurate or even missing due to the use of linear interpolation functions. On the other hands, B-spline basis functions have sufficient continuity and their derivatives are smooth enough. Therefore normal vector and curvature terms can be exactly evaluated, which eventually yields precise optimal shapes. In this article, isogeometric analysis method is utilized for the shape design optimization. By virtue of B-spline basis function, an exact geometry can be handled without finite element meshes. Moreover, initial CAD data are used throughout the optimization process, including response analysis, shape sensitivity analysis, design parameterization and shape optimization, without subsequent communication with CAD description.