• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.1
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• pp.149-159
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• 2008

In this paper, we propose a blind watermarking algorithm of 3d mesh model using spherical parameterization. Spherical parameterization is a useful method which is applicable to 3D data processing. Especially, orthogonal coordinate can not analyse the feature of the vertex coordination of the 3D mesh model, but this is possible to analyse and process. In this paper, the centroid center of the 3D model was set to the origin of the spherical coordinate, the orthogonal coordinate system was transformed to the spherical coordinate system, and then the spherical parameterization was applied. The watermark was embedded via addition/modification of the vertex after the feature analysis of the geometrical information and topological information. This algorithm is robust against to the typical geometrical attacks such as translation, scaling and rotation. It is also robust to the mesh reordering, file format change, mesh simplification, and smoothing. In this case, the this algorithm can extract the watermark information about $90{\sim}98%$ from the attacked model. This means it can be applicable to the game, virtual reality and rapid prototyping fields.

• KIPS Transactions on Software and Data Engineering
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• v.11 no.12
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• pp.525-530
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• 2022

Although the iterative closest point (ICP) algorithm has been widely used to align two point clouds, ICP tends to fail when the initial orientation of the two point clouds are significantly different. In this paper, when two triangular meshes A and B have significantly different initial orientations, we present an algorithm to align them. After obtaining weighted centroids for meshes A and B, respectively, vertices that are likely to correspond to each other between meshes are set as feature points using the distance from the centroid to the vertices. After rotating mesh B so that the feature points of A and B to be close each other, RMSD (root mean square deviation) is measured for the vertices of A and B. Aligned meshes are obtained by repeating the same process while changing the feature points until the RMSD is less than the reference value. Through experiments, we show that the proposed algorithm aligns the mesh even when the ICP and Go-ICP algorithms fail.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4C
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• pp.472-484
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• 2004

We proposed 3D mesh watermarking algorithm using CEGI distribution. In the proposed algorithm, we divide a 3D mesh of VRML data into 6 patches using distance measure and embed the same watermark bits into the normal vector direction of meshes that mapped into the cells of each patch that have the large magnitude of complex weight of CEGI. The watermark can be extracted based on the known center point of each patch and order information of cell. In an attacked model by affine transformation, we accomplish the realignment process before the extraction of the watermark. Experiment results exhibited the proposed algorithm is robust by extracting watermark bit for geometrical and topological deformed models.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.12C
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• pp.1194-1202
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• 2007

In this paper, we proposed a blind watermarking algorithm to apply to the rapid prototyping system. The 3D mesh model is used in the step of the CAD modeling before the making of the prototype system of the rapid prototyping system. STL type mesh modeling which is used in this system reduces the error of the system and improves the accuracy of the system. In the step of the CAD modeling, some transformations which do not change the model accuracy are used, but some transformations which change the model accuracy are not used because the mesh model error is related to the accuracy of the prototype system. Most watermarking algorithms embedded a specific random noise as the watermark information into the model. These kinds of the algorithms are not proper to the 3D model watermarking. The proposed algorithm can be used for the accurate prototyping system because it does not change the model after the watermark embedding This means it can be used for the copyright marking and the data integrity.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04c
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• pp.184-186
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• 2003

본 논문에서는 대규모 지형 데이터를 이용한 네트웍 환경에서의 지형 탐색을 위한 다중 해상도 기법과 prefetching 기법을 제안한다. 지형 렌더링에 널리 사용되는 직각이등변 삼각형 메쉬 형태의 DEM 데이터를 정삼각형 메친 데이터로 재구성한 뒤, 이를 다중 해상도로 구조화하여. 네트웍 환경에서의 주요 문제점인 대역폭과 지연 문제를 보완하였다. 본 기법은 3차원 지형 데이터를 이용한 온라인 게임 등에 응용될 수 있다.

• Proceedings of the Korea Multimedia Society Conference
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• 2000.11a
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• pp.467-470
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• 2000

이 논문에서는 대용량 3 차원 데이터를 효율적 편집과 실시간 랜더링하는 방법라 자료구조를 제안한다. 3 차원 스캐닝 데이터로부터 만들어지는 대용량 폴리곤 데이터를 사용자 인터페이스를 이용하여 실시간에 편집하기 위한 효율적인 자료·구조를 제안하고, 이를 이용한 포리곤 연산자의 구현 방법 설명하고 있다. 또한, 여기서 제안한 자료구조가 기존 edge 기반 자료구조와의 성능비교를 통해 대용량 메쉬 데이터 편집시스템에 적합한 자료구조임을 보이겠다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.3
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• pp.120-126
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• 2001

The simulation system for analyzing the ceramic drying process is developed. This system consists of 3 parts: pre-processor, analyzer, and post-processor. The pre-processor creates 3-dimensional ceramics, makes finite-element models, and prepares analyzers input. The analyzer computes temperature, moisture, residual stress, displacement, etc. during the drying process using the information about finite-element model, material property, and boundary condition provided by the pre-processor. In post-processor, the analyzers results are visualized to help designers evaluation of the drying of the ceramic.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.230-233
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• 2009

본 논문은 볼륨 데이터를 입력받아 계층성을 지원하는 등밀도 표면을 재구성하는 방법을 제안한다. 제안된 방법은 먼저 입력 볼륨 데이터에서 볼륨 피라미드를 구성하고 해상도가 최저인 피라미드의 최상단 볼륨에서부터 셀경계표현 방법을 이용하여 조악한 초기 메쉬를 생성하며, 이 메쉬를 표면축소기법을 사용하여 반복적으로 변형하여 O(3)-인접성 조건하에서 추출한 등밀도점을 잘 근사할 수 있도록 한다. 제안된 방법은 생성되는 표면이 압축이나 점진적인 전송 등과 같은 다중 해상도 알고리즘에 활용될 수 있다는 장점이 있다.

• Journal of Broadcast Engineering
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• v.14 no.3
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• pp.322-331
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• 2009

This paper proposes an efficient data representation of stereo images using edge-based mesh optimization. Mash-based two dimensional warping for stereo images mainly depends on the performance of a node selection and a disparity estimation of selected nodes. Therefore, the proposed method first of all constructs the feature map which consists of both strong edges and boundary lines of objects for node selection and then generates a grid-based mesh structure using initial nodes. The displacement of each nodal position is iteratively estimated by minimizing the predicted errors between target image and predicted image after two dimensional warping for local area. Generally, iterative two dimensional warping for optimized nodal position required a high time complexity. To overcome this problem, we assume that input stereo images are only horizontal disparity and that optimal nodal position is located on the edge include object boundary lines. Therefore, proposed iterative warping method performs searching process to find optimal nodal position only on edge lines along the horizontal lines. In the experiments, we compare our proposed method with the other mesh-based methods with respect to the quality by using Peak Signal to Noise Ratio (PSNR) according to the number of nodes. Furthermore, computational complexity for an optimal mesh generation is also estimated. Therefore, we have the results that our proposed method provides an efficient stereo image representation not only fast optimal mesh generation but also decreasing of quality deterioration in spite of a small number of nodes through our experiments.

• The KIPS Transactions:PartA
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• v.11A no.7 s.91
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• pp.555-562
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• 2004

Both global volume reduction and local shape changes of hippocampus within the brain indicate their abnormal neurological states. Hippocampal shape analysis consists of two main steps. First, construct a hippocampal shape representation model ; second, compute a shape similarity from this representation. This paper proposes a novel method for the analysis of hippocampal shape using integrated Octree-based representation, containing meshes, voxels, and skeletons. First of all, we create multi-level meshes by applying the Marching Cube algorithm to the hippocampal region segmented from MR images. This model is converted to intermediate binary voxel representation. And we extract the 3D skeleton from these voxels using the slice-based skeletonization method. Then, in order to acquire multiresolutional shape representation, we store hierarchically the meshes, voxels, skeletons comprised in nodes of the Octree, and we extract the sample meshes using the ray-tracing based mesh sampling technique. Finally, as a similarity measure between the shapes, we compute $L_2$ Norm and Hausdorff distance for each sam-pled mesh pair by shooting the rays fired from the extracted skeleton. As we use a mouse picking interface for analyzing a local shape inter-actively, we provide an interaction and multiresolution based analysis for the local shape changes. In this paper, our experiment shows that our approach is robust to the rotation and the scale, especially effective to discriminate the changes between local shapes of hippocampus and more-over to increase the speed of analysis without degrading accuracy by using a hierarchical level-of-detail approach.