• Proceedings of the Korean Information Science Society Conference
• /
• 2003.10b
• /
• pp.667-669
• /
• 2003

특징 형상의 조합으로 표현될 수 없는 자유 형상을 가진 제품이 늘어남에 따라 자유형상을 효율적으로 변형시키는 기법이 필요하다. 여러 가지 자유형상 변형기법(FFD) 가운데에서 자유 형상을 파라메트릭하게 컨트롤하기 위해서는 조정 다각형 기반의 형상 변형 기법이 적합하다. 이에 따라 본 연구에서는 FFD 기법을 적용하여 자유형상 모델을 파라메트릭하게 컨트롤하기 위해 입력 모델에 대한 조정 다각형을 자동으로 생성하는 알고리즘을 제안하였다. 제안된 알고리즘은 크게 기본 조정 다각형 생성과 조정 다각형 최적화 단계로 나누어진다. 기본 다각형 생성에서는 1)입력모델을 직교 3방향에 투영, 2)투영된 결과에 대해 2차원 조정 다각형을 생성, 3)2차원 조정 다각형을 조합하여 3차원 기본 조정 다각형 생성의 단계를 거친다. 조정 다각형 최적화 단계에서는 기본 조정 다각형에 에지 및 면 연산자를 적용하여 입력 모델에 더욱 근사하는 최종 조정 다각형을 생성한다. 예제에서는 제안된 알고리즘을 통해 자동으로 생성된 조정다각형을 자동차 모델에 적용하여 모델의 형상을 변화시킨 결과를 보였다.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
• /
• 1998.11a
• /
• pp.99-104
• /
• 1998

3차원 형상정보 추출기술은 3D스캐너에 활용되어 실물의부터 3차원 모델을 생성하는데 사용되고 있다. 현재까지 주로 사용되는 기술은 레이저광을 이용하여 3차원 모델을 만드는 기술과 스테레오기법에 의한 방법들이 사용되고 있었다. 본 논문에서는 모아레기법을 사용하여 영상정보를 프레임단위로 해석함으로써 3차원 형상 정보를 빠른 시간내에 추출하고, 수평 360도 방향에 대해서는 3∼4프레임을 해석하여 형상정보를 통합하였고, 이로부터 3차원 모델을 생성하였다. 모아레기법의 장점은 3차원 정보를 레이저기법보다 정밀하게 추출할 수가 있었다. 본 논문에서는 모아레영상을 해석하여 3차원 형상정보를 추출하는 방법, 추출된 3차원 형상으로부터 메쉬최적화와 텍스춰매핑(Texture Mapping)을 사용하여 3차원 모델을 형성하는 방법들을 제안한다.

• Journal of Korean Association for Spatial Structures
• /
• v.10 no.4
• /
• pp.113-122
• /
• 2010

Space frame structures are included in the large spatial structures and can adopt various structure types. But, it is not easy to choose the optimal member size and shape because it depends on the structural engineer's experience and the repeated trial and error. Therefore, in this study, the final goal is to help the designer with the selection of the optimum shape. First, various space frame structures with ellipse dome and vault complex types are chosen and the shape generation method is considered to generate the nodes, coordinates and members. In optimal design process of space frame structure, each node coordinate changes according to height variation or the number of rings. Therefore, the auto generation technique of nodes and members is required in order to consider this phenomenon in optimal design process. Next, the shape generation module is created, base on the shape generation method. This module is connected with the analysis module and the optimization algorithm. Finally, the example model is presented for the evaluation of the efficiency of optimization algorithms.

• Journal of the Korea Computer Graphics Society
• /
• v.22 no.2
• /
• pp.20-26
• /
• 2016

This paper proposes an automatic hexahedral mesh generation method, in which internal medial surfaces are established to partition a region using the face-offsetting method. In order to test the usability of the suggested method, aspect ratios and Jacobians of the generated mesh for two models are evaluated and compared with ones from existing methods. It is verified that the proposed medial surface generation and partitioning scheme based on the face-offsetting method can be effectively used in the automatic hexahedral mesh generation procedure.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.10 no.1
• /
• pp.127-135
• /
• 2006

The image-based 3D modeling is the technique of generating a 3D graphic model from images acquired using cameras. It is being researched as an alternative technique for the expensive 3D scanner. In this paper, I propose the image-based 3D modeling system using calibrated camera. The proposed algorithm for rendering 3D model is consisted of three steps, camera calibration, 3D shape reconstruction and 3D surface generation step. In the camera calibration step, I estimate the camera matrix for the image aquisition camera. In the 3D shape reconstruction step, I calculate 3D volume data from silhouette using pyramidal volume intersection. In the 3D surface generation step, the reconstructed volume data is converted to 3D mesh surface. As shown the result, I generated relatively accurate 3D model.

• Journal of Korean Association for Spatial Structures
• /
• v.10 no.2
• /
• pp.77-86
• /
• 2010

This paper provides background theories and numerical results of automatic finite element (FE) mesh generation for freeform discrete structures. The present method adopts the computer aided geometric design (CAGD) technique to overcome the limitation of case-sensitive traditional automatic FE mesh generator. The present technique involves two steps. The first one is to represent the shape of the structure using the geometric model based on the CAGD and the second one is to generate the discrete FE mesh of spatial structures over the geometric model. From numerical results, it is found to be that the present technique is very easy to produce the FE mesh for free-form spatial structures and it can also reuse some features of traditional automatic mesh generator in the process. Furthermore, it shows the possibility to be used for the shape optimization of large spatial structures.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.19 no.2
• /
• pp.230-235
• /
• 2009

This paper describes an automatic finite element mesh generation for finite element analysis of three-dimensional structures. It is consisting of fuzzy knowledge processing, bubble meshing and solid geometry modeler. This novel mesh generation process consists of three subprocesses: (a) definition of geometric model, i.e. analysis model, (b) generation of bubbles, and (c) generation of elements. One of commercial solid modelers is employed for three-dimensional solid structures. Bubble is generated if its distance from existing bubble points is similar to the bubble spacing function at the point. The bubble spacing function is well controlled by the fuzzy knowledge processing. The Delaunay method is introduced as a basic tool for element generation. Automatic generation of finite element for three-dimensional solid structures holds great benefits for analyses. Practical performances of the present system are demonstrated through several mesh generations for 3D geometry.

• Journal of KIISE:Computing Practices and Letters
• /
• v.16 no.11
• /
• pp.1096-1100
• /
• 2010

In this paper, we propose an automatic segmentation of the meniscus based on active shape model using interpolated shape information in MR images. First, the statistical shape model of meniscus is constructed to reflect the shape variation in the training set. Second, the generation technique of interpolated shape information by using the weight according to shape similarity is proposed to robustly segment the meniscus with large variation. Finally, the automatic meniscus segmentation is performed through the active shape model fitting. For the evaluation of our method, we performed the visual inspection, accuracy measure and processing time. For accuracy evaluation, the average distance difference between automatic segmentation and semi-automatic segmentation are calculated and visualized by color-coded mapping. Experimental results show that the average distance difference was $0.54{\pm}0.16mm$ in medial meniscus and $0.73{\pm}0.39mm$ in lateral meniscus. The total processing time was 4.87 seconds on average.

• Journal of the Korea Computer Graphics Society
• /
• v.23 no.5
• /
• pp.29-38
• /
• 2017

We propose a method for tree-inspired chair modeling that can generate a tree-branch pattern in the skeleton of an arbitrary chair shape. Unlike existing methods that merge multiple-input models, the proposed method requires only one mesh as input, namely the contour mesh of the user's desired part, to model the chair with a branch pattern generated by tree-growth simulation. We propose a new method for the efficient extraction of the contour-mesh region in the tree-branch pattern. First, we extract the contour mesh based on the face area of the input mesh. We then use the front and back mesh information to generate a skeleton mesh that reconstructs the connection information. In addition, to obtain the tree-branch pattern matching the shape of the input model, we propose a three-way tree-growth simulation method that considers the tangent vector of the shape surface. The proposed method reveals a new type of furniture modeling by using an existing furniture model and simple parameter values to model tree branches shaped appropriately for the input model skeleton. Our experiments demonstrate the performance and effectiveness of the proposed method.

• Journal of Broadcast Engineering
• /
• v.14 no.1
• /
• pp.81-84
• /
• 2009

This paper explores the possibility of describing objects from the change in the shape according to the change in viewpoint. Specifically, we sample the shapes from various viewpoints of a 3-D model, and apply dimension reduction by locally linear embedding. A low dimensional distribution of points are constructed, and characteristics of the object are described from this distribution. Also, we propose two 3-D retrieval methods by applying the iterative closest point algorithm, and by applying Fourier transform and measuring similarity by modified Housdorff distance, and present experimental results. The proposed method shows that the change of shape according to the change in viewpoint can describe the characteristics of an object.