• Title/Summary/Keyword: normal vector

Search Result 146, Processing Time 0.094 seconds

Frictional Contact Model for Finite Element Analysis of Sheet-Metal Forming Processes (박판 성형 공정의 유한요소 해석을 위한 마찰접촉 모델)

  • 금영탁
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.17 no.9
    • /
    • pp.2242-2251
    • /
    • 1993
  • The mesh-based frictional contact model has been developed which does not rely on the spatial derivatives of the tool surface. Only points on the surface are evaluated from the description. which can then be simplified because of the relaxed demands placed on it. The surface tangents, normals, and corresponding derivatives at each finite-element node are evaluated directly from the finite-element mesh, in terms of the connecting nodal positions. The advantages accrue because there is no longer a need for a smooth tool surface to assure reasonable normals and derivatives. Furthermore, it can be shown that the equilibrium equations can only be properly written with a special normal derived from the mesh itself. The validity, accuracy, computation time, and stability of mesh-based contact model were discussed with the numerical examples of rounded flat-top and rough, flat-top rounded punch forming operations. Also, the forming process of a automobile inner panel section was simulated for testing the robustness of new contact model. In the discussion, the superiority of new model was examined, comparing with tool-based contact one.

Acceleration of Mesh Denoising Using GPU Parallel Processing (GPU의 병렬 처리 기능을 이용한 메쉬 평탄화 가속 방법)

  • Lee, Sang-Gil;Shin, Byeong-Seok
    • Journal of Korea Game Society
    • /
    • v.9 no.2
    • /
    • pp.135-142
    • /
    • 2009
  • Mesh denoising is a method to remove noise applying various filters. However, those methods usually spend much time since filtering is performed on CPU. Because GPU is specialized for floating point operations and faster than CPU, real-time processing for complex operations is possible. Especially mesh denoising is adequate for GPU parallel processing since it repeats the same operations for vertices or triangles. In this paper, we propose mesh denoising algorithm based on bilateral filtering using GPU parallel processing to reduce processing time. It finds neighbor triangles of each vertex for applying bilateral filter, and computes its normal vector. Then it performs bilateral filtering to estimate new vertex position and to update its normal vector.

  • PDF

Graph-based Segmentation for Scene Understanding of an Autonomous Vehicle in Urban Environments (무인 자동차의 주변 환경 인식을 위한 도시 환경에서의 그래프 기반 물체 분할 방법)

  • Seo, Bo Gil;Choe, Yungeun;Roh, Hyun Chul;Chung, Myung Jin
    • The Journal of Korea Robotics Society
    • /
    • v.9 no.1
    • /
    • pp.1-10
    • /
    • 2014
  • In recent years, the research of 3D mapping technique in urban environments obtained by mobile robots equipped with multiple sensors for recognizing the robot's surroundings is being studied actively. However, the map generated by simple integration of multiple sensors data only gives spatial information to robots. To get a semantic knowledge to help an autonomous mobile robot from the map, the robot has to convert low-level map representations to higher-level ones containing semantic knowledge of a scene. Given a 3D point cloud of an urban scene, this research proposes a method to recognize the objects effectively using 3D graph model for autonomous mobile robots. The proposed method is decomposed into three steps: sequential range data acquisition, normal vector estimation and incremental graph-based segmentation. This method guarantees the both real-time performance and accuracy of recognizing the objects in real urban environments. Also, it can provide plentiful data for classifying the objects. To evaluate a performance of proposed method, computation time and recognition rate of objects are analyzed. Experimental results show that the proposed method has efficiently in understanding the semantic knowledge of an urban environment.

Robust surface segmentation and edge feature lines extraction from fractured fragments of relics

  • Xu, Jiangyong;Zhou, Mingquan;Wu, Zhongke;Shui, Wuyang;Ali, Sajid
    • Journal of Computational Design and Engineering
    • /
    • v.2 no.2
    • /
    • pp.79-87
    • /
    • 2015
  • Surface segmentation and edge feature lines extraction from fractured fragments of relics are essential steps for computer assisted restoration of fragmented relics. As these fragments were heavily eroded, it is a challenging work to segment surface and extract edge feature lines. This paper presents a novel method to segment surface and extract edge feature lines from triangular meshes of irregular fractured fragments. Firstly, a rough surface segmentation is accomplished by using a clustering algorithm based on the vertex normal vector. Secondly, in order to differentiate between original and fracture faces, a novel integral invariant is introduced to compute the surface roughness. Thirdly, an accurate surface segmentation is implemented by merging faces based on face normal vector and roughness. Finally, edge feature lines are extracted based on the surface segmentation. Some experiments are made and analyzed, and the results show that our method can achieve surface segmentation and edge extraction effectively.

A Voxelization for Geometrically Defined Objects Using Cutting Surfaces of Cubes (큐브의 단면을 이용한 기하학적인 물체의 복셀화)

  • Gwun, Ou-Bong
    • The KIPS Transactions:PartA
    • /
    • v.10A no.2
    • /
    • pp.157-164
    • /
    • 2003
  • Volume graphics have received a lot of attention as a medical image analysis tool nowadays. In the visualization based on volume graphics, there is a process called voxelization which transforms the geometrically defined objects into the volumetric objects. It enables us to volume render the geometrically defined data with sampling data. This paper suggests a voxeliration method using the cutting surfaces of cubes, implements the method on a PC, and evaluates it with simple geometric modeling data to explore propriety of the method. This method features the ability of calculating the exact normal vector from a voxel, having no hole among voxels, having multi-resolution representation.

Inverse kinematics of a Reclaimer: Redundancy and a Closed- Form Solution by Exploiting Geometric Constraints (원료불출기의 역기구학: 여유자유도와 구속조건을 이용한 닫힌 형태의 해)

  • Hong, K.S.;Kim, Y.M.;Shin, K.T.
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.14 no.7
    • /
    • pp.144-153
    • /
    • 1997
  • The inverse kinematics problem of a reclaimer which excavates and transports raw materials in a raw yard is investigated. Because of the geometric feature of the equipment in which scooping buckets are attached around the rotating disk, kinematic redundancy occurs in determining joint variable. Link coordinates are introduced following the Denavit-Hartenbery representation. For a given excavation point the forward kinematics yields 3 equations, however the number of involved joint variables in the equations is four. It is shown that the rotating disk at the end of the boom provides an extra passive degree of freedom. Two approaches are investigated in obtaining inverse kinematics solutions. The first method pre-assigns the height of excavation point which can be determined through path planning. A closed form solution is obtained for the first approach. The second method exploits the orthogonality between the normal vector at the excavation point and the z axis of the end-effector coordinate system. The geometry near the reclaiming point has been approximated as a plane, and the plane equation has been obtained by the least square method considering 8 adjacent points near the point. A closed form solution is not found for the second approach, however a linear approximate solution is provided.

  • PDF

A Digital Watermarking of 3D Geometric Model STL for Rapid Prototyping System (쾌속조형 시스템을 위한 3차원 기하학적 형상인 STL의 디지털 워터마킹)

  • 김기석;천인국
    • Journal of Korea Multimedia Society
    • /
    • v.5 no.5
    • /
    • pp.552-561
    • /
    • 2002
  • In this paper, a new watermarking algorithm for STL files which contains 3D geometric information as triangular facets is proposed. STL files are widely used in rapid prototyping industry as a standard interchange format. The proposed algorithm inserts multi-bit watermark information into the surface normal vector and vertex description area of STL file without distorting the original 3D geometric information. According to the watermark bits, the position of normal vector and the direction of vertex sequence are modulated. The proposed algorithm is robust to the attack of changing the order of the triangular meshes. In addition, the invisibility requirement is also satisfied. Experiment results show that the proposed algorithm can encode and decode watermark bits into the various STL files without any distortion of 3D shape.

  • PDF

Indoor environment recognition based on depth image (깊이 영상 기반 실내 공간 인식)

  • Kim, Su-Kyung;Choi, Hyung-Il
    • Journal of the Korea Society of Computer and Information
    • /
    • v.19 no.11
    • /
    • pp.53-61
    • /
    • 2014
  • In this paper, we propose a method using an image received by the depth camera in order to separate the wall in a three-dimensional space indoor environment. Results of the paper may be used to provide valuable information on the three-dimensional space. For example, they may be used to recognize the indoor space, to detect adjacent objects, or to project a projector on the wall. The proposed method first detects a normal vector at each point by using the three dimensional coordinates of points. The normal vectors are then clustered into several groups according to similarity. The RANSAC algorithm is applied to separate out planes. The domain knowledge helps to determine the wall among planes in an indoor environment. This paper concludes with experimental results that show performance of the proposed method in various experimental environment.

Photometry Data Compression for Three-dimensional Mesh Models Using Connectivity and Geometry Information (연결성 정보와 기하학 정보를 이용한 삼차원 메쉬 모델의 광학성 정보 압축 방법)

  • Yoon, Young-Suk;Ho, Yo-Sung
    • Journal of the Institute of Electronics Engineers of Korea CI
    • /
    • v.45 no.3
    • /
    • pp.160-174
    • /
    • 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.

Comparisons of Putting Stroke Characteristics between Expert and Novice Golfers(II) (숙련자와 초보자의 퍼팅 스트로크 특성비교(II))

  • Park, Jin;Lee, Young-Sup;Ahn, Byoung-Hwa
    • Korean Journal of Sport Biomechanics
    • /
    • v.12 no.2
    • /
    • pp.207-214
    • /
    • 2002
  • The purpose of this study was to examine the putter head movement during the putting strokes. Highly skilled 5 golfers(less than 3 handicaps) and 5 novice golfers(having no golf experience) participated in this study. A target distance was 3 m. Movements of the putter head were recorded at 60 Hz with two video cameras(1/500 shutter speed). The results showed that the angle of the clubface of expert golfers was almost 1 degree, but the novice golfers were more than 6 degrees. Expert golfers moved their hands faster than the head movement, therefore the clubface was not opened during impact. However, the novice golfers moved their hands slower than the head movement, therefore the clubface was opened during impact. The ratio of input and output angles of total movement was 1:3-4, however, the ratio of input and output angles of impact zone was 1:2. The angle of normal vector of expert golfers was less than the angle of normal vector of novice golfers.