• Journal of the Institute of Electronics Engineers of Korea SP
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• v.40 no.6
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• pp.132-140
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• 2003

In this paper, we propose a new scheme for view-dependent transmission of three-dimensional (3-D) polygonal mesh models with hierarchial partitioning. In order to make a view-dependent representation of 3-D mesh models, we combine sequential and progressive mesh transmission techniques. By setting higher priorities to visible parts than invisible parts, we can obtain good qualify of 3-D models in a limited transmission bandwidth. In this paper, we use a multi -layer representation of 3-D mesh models based on hierarchical partitioning. After representing the 3-D mesh model in a hierarchical tree, we determine resolutions of partitioned submeshes in the last level. Then, we send 3-D model data by view-dependent selection using mesh merging and mesh splitting operations. By the partitioned mesh merging operation, we can reduce the joint boundary information coded redundantly in the partitioned submeshes. We may transmit additional mesh information adaptively through the mesh spritting operation.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.40 no.3
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• pp.185-193
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• 2003

The conventional parallelogram prediction uses only three previously traversed vertices in a single adjacent triangle; thus, the predicted vertex can be located at a biased position. Moreover, vortices on curved surfaces may not be predicted effectively since each parallelogram is assumed to lie on the same plane. In order to improve the prediction performance, we use all the neighboring vertices that precede the current vertex. After we order vortices using a vertex layer traversal algorithm, we estimate the current vertex position based on observations of the previously coded vertex positions in the layer traversal order. The difference between the original and the predicted vertex coordinate values is encoded by a uniform quantizer and an entropy coder. The proposed scheme demonstrates improved coding efficiency for various VRML test data.

• The KIPS Transactions:PartA
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• v.12A no.1 s.91
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• pp.13-22
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• 2005

Similarly to the edges defined in a 2D image, we can define the geometric features representing the boundary of the distinctive parts appearing on 3D meshes. The geometric features have been used as basic primitives in several applications such as mesh simplification, mesh deformation, and mesh editing. In this paper, we propose geometric livewire and geometric livelane for extracting geometric features in a 3D mesh, which are the extentions of livewire and livelane methods in images. In these methods, approximate curvatures are adopted to represent the geometric features in a 3D mesh and the 3D mesh itself is represented as a weighted directed graph in which cost functions are defined for the weights of edges. Using a well-known shortest path finding algorithm in the weighted directed graph, we extracted geometric features in the 3D mesh among points selected by a user. In this paper, we also visualize the results obtained from applying the techniques to extracting geometric features in the general meshes modeled after human faces, cows, shoes, and single teeth.

• Proceedings of the Korean Information Science Society Conference
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• 2007.06b
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• pp.167-170
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• 2007

본 논문에서는 텍스춰매핑, 재메쉬화, 메쉬의 단순화와 모핑 및 압축 등 다양한 분야에 적용되는 메쉬분할 문제를 다룬다. 메쉬분할은 주어진 삼차원 메쉬를 서로 떨어진 집합(disjoint sets)으로 분할하는 것으로서 여러 연구자들에 의해 많은 연구 결과들이 제시되어 왔다. 본 논문에서는 삼차원 메쉬가 가지고 있는 기하학적 특성을 고려하여 메쉬를 분할하는 방법을 제시하고자 한다. 먼저 메쉬의 국부적 기하 특성인 곡률 정보와 전역적 기하 특성인 볼록성을 이용하여 삼차원 메쉬를 구성하는 첨예정점을 추출하였고, 이들간의 거리 정보를 이용하여 이 첨예정점들을 군집화(clustering)하였다. 최종 메쉬분할을 위해 분할된 첨예정점에 속하지 않는 나머지 정점들에 대해 거리 정보를 이용하여 군집화를 수행하였다. 본 논문에서 제안한 메쉬분할 방법을 검증하기 위해 벤치마크로 공개된 여러 메쉬 모델에 대해 실험하여 그 결과를 보여주었다.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.41 no.4
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• pp.113-123
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• 2004

This paper presents a new collusion-secure fingerprinting scheme to embed fingerprints into three-dimensional(3-D) mesh models efficiently. In the proposed scheme, we make the same number of fingerprints as the number of customers based on the finite projective geometry, partition a 3-D mesh model related to the number of bits assigned to each fingerprint and then embed a watermark representing copyright information into each submesh to be marked. Considering imperceptibility and robustness of the watermarking algorithm we embed the watermark signal into mid-frequency DCT coefficients obtained by transforming vertex coordinates in the triangle strips which are generated from the submeshes to be marked. Experimental results show that our scheme is robust to additive random noises, MPEG-4 SNHC 3-D mesh coding, geometrical transformations, and fingerprint attacks by two traitors' collusion. In addition, we can reduce the number of bits assigned to each fingerprint significantly.

• The Journal of the Korea Contents Association
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• v.10 no.4
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• pp.106-114
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• 2010

Mesh parameterization is the process of finding one-to-one mapping between an input mesh and a parametric domain. It has been considered as a fundamental tool for digital geometric processing which is required to develop several applications of digital geometries. In this paper, we propose a novel 3D volume parameterization by means that a harmonic mapping is established between a 3D volume mesh and a unit solid cube. To do that, we firstly partition the boundary of the given 3D volume mesh into the six different rectangular patches whose adjacencies are topologically identical to those of a surface cube. Based on the partitioning result, we compute the boundary condition as a precondition for computing a volume mesh parameterization. Finally, the volume mesh parameterization with a low-distortion can be accomplished by performing a harmonic mapping, which minimizes the harmonic energy, with satisfying the boundary condition. Experimental results show that our method is efficient enough to compute 3D volume mesh parameterization for several models, each of whose topology is identical to a solid sphere.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2002.11a
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• pp.93-98
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• 2002

MPEG-4 SNHC 표준에서 사용되는 평행사변형 예측방법은 예측하고자 하는 꼭지점이 인접한 꼭지점들과 같은 평면상에 있다고 가정하여 하나의 삼각형 내에 있는 인접한 세 개의 꼭지점 좌표 값만을 이용하므로 예측 효율이 좋지 않다. 본 논문에서는 삼각형 주변의 꼭지점 좌표 값과 인접하는 삼각형 사이의 사잇각을 고려한 통합예측을 이용하여 삼차원 메쉬 모델의 기하정보를 부호화하는 방법을 제안한다. 우선 꼭지점 계층탐색 방법으로 위상학적으로 거리가 가까운 점들을 탐색하여 정렬된 값들의 기하학적 상관도를 높이고, 정렬된 삼차원 메쉬의 꼭지점 순서에 따라 주변의 꼭지점 값들을 이용하여 현재 꼭지점 값을 예측한다. 본 논문에서 제안한 통합예측 방법은 다양한 VRML 포맷의 테스트 모델에 대해서 기존의 MPEG-4 SNHC의 평행사변형 예측 방법보다 우수한 성능을 보인다.

• Journal of KIISE
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• v.43 no.4
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• pp.419-429
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• 2016

Generating a 3D surface model from coronary artery segmentation helps to not only improve the rendering efficiency but also the diagnostic accuracy by providing physiological informations such as fractional flow reserve using computational fluid dynamics (CFD). This paper proposes a method to generate a triangular surface mesh using vessel structure information acquired with coronary artery segmentation. The marching cube algorithm is a typical method for generating a triangular surface mesh from a segmentation result as bit mask. But it is difficult for methods based on marching cube algorithm to express the lumen of thin, small and winding vessels because the algorithm only works in a three-dimensional (3D) discrete space. The proposed method generates a more accurate triangular surface mesh for each singular vessel using vessel centerlines, normal vectors and lumen diameters estimated during the process of coronary artery segmentation as the input. Then, the meshes that are overlapped due to branching are processed by mesh merging and merged into a coronary mesh.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.125-128
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• 2001

본 논문은 파동분할(Wave partitioning) 방식을 이용한 순차적(Sequential) 메쉬 부호화 방식을 제안한다. 파동분할 방식은 호수에 물방울이 퍼져 나가는 자연 원리를 이용하여 초기 삼각형의 주위에 삼각형을 덧붙여 가면서 하나의 SPB(Small Processing Block)을 만들어내는 방식이다. 이 방식을 이용하여 하나의 모델을 서로 독립적인 SPB로 분할하고, 각각의 SPB 내에서 초기 삼각형을 중심으로 그것에 덧붙여진 삼각형에 의해 만들어진 원 또는 반원을 찾는다. 또한 그 원주를 따라 순차적으로 꼭지점을 구하면 각각의 꼭지점들은 일정한 패턴으로 늘어서게 되고, 이를 이용하여 연결성 정보 없이 부가 정보만 이용하여 모델을 순차적으로 무손실 부호화한다.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.3
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• pp.160-174
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• 2008

In this paper, we propose new coding techniques for photometry data of three-dimensional(3-D) mesh models. We make a good use of geometry and connectivity information to improve coding efficiency of color, normal vector, and texture data. First of all, we determine the coding order of photometry data exploiting connectivity information. Then, we exploit the obtained geometry information of neighboring vortices through the previous process to predict the photometry data. For color coding, the predicted color of the current vertex is computed by a weighted sum of colors for adjacent vortices considering geometrical characteristics between the current vortex and the adjacent vortices at the geometry predictor. For normal vector coding, the normal vector of the current vertex is equal to one of the optimal plane produced by the optimal plane generator with distance equalizer owing to the property of an isosceles triangle. For texture coding, our proposed method removes discontinuity in the texture coordinates and reallocates texture image segments according to the coding order. Simulation results show that the proposed compression schemes provide improved performance over previous works for various 3-D mesh models.