Associate Professor
System Design and Modeling Lab.
Graduate School of Information Science and Technology
Hokkaido University
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Object Recognition in Terrestrial Laser Scan Data using Spin Images
This paper describes a method of object recognition in terrestrial laser scan data of complex scenes. By local 3D shape matching between the CAD model mesh of the object and the laser scan data of the scene, the existence of the object is recognized and its location and orientation in the scene are extracted. Spin-images are used for shape matching. In this paper, some techniques for applying spin-image matching to the terrestrial laser scan data are proposed. They include robustness improvements for the scan noise and the differences in vertex densities by normal averaging and uniform point sampling, and efficient calculation by using multiresolution images and geometric point filtering. Hiroaki Date, Yusuke Kaneta, Akihiro Hatsukaiwa, Masahiko Onosato and Satoshi Kanai, Object Recognition in Terrestrial Lase Scan Data using Spin Images, CAD'11 conference and exhibition, PaperNumber:83 (2011) |
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An Interactive Cutaway Model Representation System using a Three-dimensional User Interface
Understanding complex models, which have complex internal structures or consist of many parts, is strongly required in many 3D applications. In this paper, we propose an interactive cutaway model representation system using a three-dimensional user interface for an easier understanding of the complex models. The cutaway model is the result of the difference Boolean operation between an input model and an arbitrary cutting volume. Our system enables users to change each position and orientation of the input model and the cutting volume intuitively and simultaneously using two 6DOF input devices. Therefore, users can easily see internal structures at the region of interest. In addition, our system enables users to understand the input model by seeing the cutaway model stereoscopically, and by touching it with haptic force feedback. In our system, the input model and the cutting volume are represented by triangular mesh models. We introduced the method for a cutaway model generation of the input model. In this method, an efficient cutaway model representation is achieved by generating a part of the cutaway model required for seeing and touching, and rendering each set of its triangles for seeing and touching. Hiromu Furukawa, Hiroaki Date, Masahiko Onosato, An Interactive Cutaway Model Representation System using a Three-Dimensional User Interface, Proc. Design Engineering Workshop 2009, Okinawa, pp. 138-142 (2009). |
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Flexible Control of Multimaterial Tetrahedral Mesh Properties by Using Multiresolution Techniques
This paper describes a method for flexibly controlling the properties of a given multimaterial tetrahedral mesh for finite-element analysis. Our method is based on multiresolution techniques. A given mesh is first subdivided and then simplified so that the resulting mesh satisfies the user-specified thresholds for mesh properties (element size, shape, valence, and geometric tolerance). Once the simplification is completed, mesh resolution and density can be modified quickly by using level of detail. Date, H., Noguchi, S., Onosato, M., Flexible Control of Multimaterial Tetrahedral Mesh Properties by Using Multiresolution Techniques, IEEE Trans. on Magnetics, 45(3), pp. 1352-1355 (2008) |
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Development of a 3D User Interface System
for the Deformation of Mesh Models
We developed a new 3D user interface system for realizing efficiently deforming mesh models. Our system consists of two PHANToM Omnis (6DOF input and 3DOF force feedback device) and a stereoscopic display. Using this system, a user can deform a triangular mesh model and change its orientation and position simultaneously with a stereoscopic view. We show that our system enables to shorten the time of 3D manipulations required in mesh deformation through experiments. Moreover, we propose a new spatial data structure for efficient haptic rendering of the deformed triangular mesh model. This structure allows us to touch and recognize the deformed model instantly. Furukawa, H., Date, H., Onosato, M., Development of a 3D user interface system for the deformation of mesh models, Proc. IDMME-Virtual Concept 2008, (2008) |
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Fast matching, combinations extraction and configuration of mesh models using graph-based feature representation
In this paper, we propose a method for matching, combinations extraction and configuration of triangular mesh models for assembly and geometric modeling. Given two mesh models, a graph is first generated for each model. This graph, called a gfeature-graphh, represents abstract geometry information and connections of segments (local regions) for the model. Next, a set of pairs of segments which can be matched are extracted by performing sequential matching tests on the graphs. Finally, using the resulting pairs, the configuration between the models is determined by phased registrations keeping previous contact condition. An example of application to assembly modeling is included. Sato, K., Date, H., Onosato, M., Fast matching, combinations extraction and configuration of mesh models using graph-based feature representation, Proc. IDMME-Virtual Concept 2008, (2008) |
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Triangular Mesh Deformation based on Dimensions
In this paper, we propose a triangular mesh deformation method based on dimensions. By specifying the type of dimensions, the regions defining the dimensions, and the target dimensions, the mesh is automatically deformed so that it satisfies the target dimensions. Mesh deformation is based on space-based deformation using barycentric coordinates. The deformation handle, which consists of a set of triangular prisms, is automatically created by mesh segmentation, simplification and offsetting of simplified mesh. In deformation, the deformation and fixed spaces are assigned to each prism in the handle, and the mesh is deformed by applying affine transformation to the control vertices and space-based deformation to the deformation space. Results for the mechanical parts show the effectiveness of our method. Hiroaki Date and Masahiko Onosato, Triangular Mesh Deformation based on Dimensions, Computer-Aided Design and Applications (CAD'08), 5(1-4), 287-295 (2008) |
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A Multiresolution Mesh Processing System for Efficient CAE
With the progress of 3D scanning technology and storing mesh data to 3D model databases, the use of the meshes obtained by scanning and DB querying in CAE have been strongly required in addition to those obtained from traditional meshing of solid models. In our research, we developed a multiresolution mesh processing system for triangular meshes to realize CAE using various kinds of meshes. Our system consists of three functions based on the multiresolution techniques: mesh quality improvement, mesh properties control, and local mesh density control. This paper describes these functions including the extension for tetrahedral meshes, and also shows their effective use in the CAE. Hiroaki Date, Satoshi Kanai, Takeshi Kishinami and Ichiro Nishigaki, A Multiresolution Mesh Processing System for Efficient CAE, Proc. SICE-ICCAS2006, 5550-5504 (2006) |
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A Parametric Deformation Method for Mesh Models based on Barycentric Coordinates
Free-Form Deformation (FFD) is a popular method for deforming 3D geometric models. FFD first embeds the model in the parametric space defined by regular lattice (handle). Then by deforming the handle, the embedded model is deformed. However the FFD has following problems for engineering applications such as deformation of mesh models for Computer Aided Engineering: 1) It is difficult to make handle suitable for intended deformation type such as bend and twist, 2) it requires complicated manipulation to deform and 3) it can not explicitly specify the degree of deformations such as angle of bend. Therefore, in order to solve these problems, we present a parametric deformation method for mesh models. First, we propose an FFD based on barycentric coordinates (BCFFD). Then, we propose an automatic handle construction method for the BCFFD based on definition and classification of deformation types such as bend, twist and so on. Finally, we propose a parametric deformation method. Using our methods, the user can deform the mesh model by selecting deformation type and portions to be deformed, and by manipulating one or two deformation parameters. Gaku Mizuno, Hiroaki Date, Satoshi Kanai and Takeshi Kishinami, A Parametric Deformation Method for Mesh Models based on Barycentric Coordinates, Proceedings of the Sixth IASTED International Conference on Visualization, Imaging and Image Processing, 359-364 (2006) movie (avi, 16MB), pdf |
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Flexible Feature and Resolution Control of Triangular Meshes
In this paper, we propose a new feature and resolution control method of triangular meshes to realize efficient mesh uses. The basic approach of our method is to commence the production of mesh with different degrees of feature suppression and resolution from feature-removed coarse mesh by LOD technique. First, the features of the input mesh are automatically recognized using a mesh segmentation technique, and all recognized features are removed. As a result, the input mesh is decomposed into a feature-removed mesh and some feature meshes. Then, mesh simplification by edge collapse is applied to the feature-removed mesh and feature meshes. Finally, arbitrary resolution and feature-suppressed mesh can be obtained quickly by feature recovering and LOD. The effectiveness of our approach is shown through some examples and applications. Hiroaki Date, Satoshi Kanai, Takeshi Kishinami and Ichiro Nishigaki, Flexible Feature and Resolution Control of Triangular Meshes, Proceedings of the Sixth IASTED International Conference on Visualization, Imaging and Image Processing, 319-324 (2006) pdf |
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Segmentation of Scanned Mesh into Analytic Surfaces based on Robust Curvature Estimation and Region Growing
For effective application of laser or X-ray CT scanned mesh models in design, analysis, and inspection etc, it is preferable that they are segmented into desirable regions as a pre-processing. Engineering parts are commonly covered with analytic surfaces, such as planes, cylinders, spheres, cones, and tori. Therefore, the portions of the partfs boundary where each can be represented by a type of analytic surface have to be extracted as regions from the mesh model. In this paper, we propose a new mesh segmentation method for this purpose. We use the mesh curvature estimation with sharp edge recognition, and the non-iterative region growing to extract the regions. The proposed mesh curvature estimation is robust for measurement noise. Moreover, our proposed region growing enables to find more accurate boundaries of underlying surfaces, and to classify extracted analytic surfaces into higher-level classes of surfaces: fillet surface, linear extrusion surface and surface of revolution than those in the existing methods. Tomohiro Mizoguchi, Hiroaki Date, Satoshi Kanai and Takeshi Kishinami, Segmentation of Scanned Mesh into Analytic Surfaces based on Robust Curvature Estimation and Region Growing, Proc. GMP2006/Lecture Notes in Computer Science, 644-654 (2006) (Short Paper) |
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Mesh Simplification and Adaptive LOD for Finite Element Mesh Generation In this paper, we propose a new triangular finite element mesh generation method based on simplification of high-density mesh and adaptive Level-of-Detail (LOD) methods for efficient CAE. Mesh simplification evaluating mesh properties is applied to control the mesh properties required for FE mesh, such as the number of triangular elements, element shape quality and size while keeping the specified approximation tolerance. Adaptive LOD methods based on vertex hierarchy according to curvature and region of interest, and global LOD method preserving density distributions are also proposed in order to construct a more appropriate FE mesh. These methods enable efficient generation of FE meshes with appropriate properties for analysis from a high-density mesh. Finally, the effectiveness of our approach is shown through evaluations of the FE meshes for practical use. Hiroaki Date, Satoshi Kanai, Takeshi Kishinami and Ichiro Nishigaki, Mesh Simplification and Adaptive LOD for Finite Element Mesh Generation, Proc. CAD/Graphics 2005, 339-344 (2005) / International Journal of CAD/CAM, Vol.6, No.1, PaperNumber 8 (CADCG06-04) (2006) |
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A New Bilateral Mesh Smoothing Method by Recognizing Features In this paper, we propose a new mesh smoothing method for mesh models with measurement noise obtained from a 3D scanner. Our proposed method enables not only the removal of noise from the faces but the preservation and smoothing of features recognized as sharp edges and corners. First, by using the eigen analysis of normal voting tensor, mesh edges composed of sharp edges can be extracted. Second, bilateral filtering is applied to extracted mesh edges to smooth the mesh edges along the direction of the sharp edge. Finally, by applying modified bilateral filtering to the overall mesh, a mesh model with sharp edges smoothed along their directions and measurement noise removed from faces was obtained. Takafumi Shimizu, Hiroaki Date, Satoshi Kanai and Takeshi Kishinami, A New Bilateral Mesh Smoothing Method by Recognizing Features, Proc. of Ninth International Conference on Computer Aided Design and Computer Graphics, 281-286 (2005) |
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High Quality and Property Controlled Finite Element Mesh Generation from Triangular Meshes using Multiresolution Technique In this paper, we propose a new triangular finite element mesh generation scheme from various kinds of triangular meshes using multiresolution technique. Proposed scheme consists of two methods; a mesh quality improvement method and a mesh property control method. The basic strategy of these methods is a combination of the mesh subdivision and simplification. Given mesh is first subdivided to obtain enough degree of freedom for property change, then by simplification using edge collapse for resulting mesh to change the mesh properties, we can easily improve and control the mesh properties required for finite element analysis. Hiroaki Date, Satoshi Kanai, Takeshi Kishinami, Ichiro Nishigaki and Takayuki Dohi, High Quality and Property Controlled Finite Element Mesh Generation from Triangular Meshes using Multiresolution Technique, ASME Journal of Computing and Information Science in Engineering, 5(4), 266-276 (2005) |
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Textured Shape Design using Detail Extraction based on Mesh Smoothing and Flattening In this paper, we propose a new texture extraction method from an existing mesh surface with texture consisting of small bumps for efficient textured shape design. Our texture extraction approach consists of two stages: In the first stage, the geometries of base surface and texture (displacements) are separated from the textured surface using a combination of smoothing operations: the normal smoothing for estimating base surface normals, and the smoothing of vertex positions for separating geometries. The latter one is realized by moving vertices along the estimated normal direction, and it enables extraction of displacements from meshes with different properties. In the second stage, by applying mesh flattening using a parameterization technique to the estimated base surface, the initial flat mesh is generated. The final texture is then obtained by offsetting the vertices of the resulting flat mesh according to the extracted displacements. As a result, texture mesh, which represents bumpiness of the texture from base surface by the height values of the vertices, can be obtained. Hiroaki Date, Satoshi Kanai and Takeshi Kishinami, Textured Shape Design using Detail Extraction based on Mesh Smoothing and Flattening, Proceedings of the 6th International Conference on Computer-Aided Industrial Design & Conceptual Design, 146-151 (2005), extraction (avi, 8MB), texturing (avi, 18MB) |
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Multiresolution Finite Element Mesh Generation Effective and robust automatic generation methods of finite element mesh of product model are required for CAE. Although many researches for them have been done, robust mesh generation for complex solid shapes with small features and flexible mesh property control are still difficult in current finite element meshers. In this paper, we propose a new method for automatic finite element mesh generation of a product model based on multiresolution representation of high-density mesh which are stably generated by existing finite element meshers. In our approach, geometrical and topological mesh properties required for FEA can be controlled using user-specified parameters, and mesh elements corresponding to the solid model elements used for setting the analysis conditions are preserved on the simplified meshes. Using our method, robust finite element mesh generation where the mesh property is controllable could be realized. Hiroaki Date, Satoshi Kanai, Takeshi Kishinami, Ichiro Nishigaki and Takayuki Dohi, Multiresolution Finite Element Mesh Generation, Proceedings of 2004 ASME International Design Engineering Technical Conferences & Computers and Information in Engineering Conference, DETC2004-57663 (2004), movie (avi, 10MB), pdf |
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Mesh Quality Improvement based on Mesh Subdivision and Simplification Low-quality triangular meshes with extremely distorted triangles are generated from several mesh generation approaches, including reverse engineering and solid model tessellations. However, such meshes have a negative effect on mesh applications such as digital geometry processing and finite element analysis. Therefore, a robust and fast algorithm for mesh quality improvement is strongly required. In this paper, we propose a new mesh quality improvement method based on mesh subdivision and simplification. In our method, we first subdivide the input mesh until the resulting mesh has a sufficient degree of freedom for topology modification. Then by simplifying the subdivided mesh based on the edge collapse according to the measure of mesh quality improvement, we are able to obtain the high-quality mesh. Our approach also generates the multiresolution hierarchy of a high-quality triangular mesh, and it is also useful for several mesh applications. Finally, we show the effectiveness of our approach through applications with geometric models of industrial products and quantitative evaluations. Hiroaki Date, Satoshi Kanai and Takeshi Kishinami, Mesh Quality Improvement based on Mesh Subdivision and Simplification, Proceedings of 3D MODELLING 2004 (2004), movie (avi, 7MB) |
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A Prototyping System for Textured Shapes using Triangular Mesh Modeling and Stereo Lithography In this paper, we propose a new textured shape design method based on mesh-based texture integration, and introduce an efficient prototyping system of the textured shapes using stereo lithography. By using the proposed texture integration method, we can generate the mesh model with a real 3D texture, and the resulting mesh model can be directly applicable to stereo lithography. Therefore, prototypes of textured shapes can be produced efficiently. Finally, we show the effectiveness of our approach by several examples. Hiroaki Date, Satoshi Kanai, Takeshi Kishinami, Mutsuro Iwakoshi and Yoshimasa Kobayashi, A Prototyping System for Surface Textured Shapes using Triangular Mesh Modeling and Stereo Lithography, Proceedings of 2004 JAPAN-USA Symposium on Flexible Automation, JL-018 (2004) pdf |
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An Adaptive LOD Control Method for Textured Digital Terrain Model using Wavelet-based Multiresolution Representation The textured digital terrain model (TDTM) is a combination of the digital elevation model (DEM) and the surface texture model (STM). TDTMs of extreme complexity have come to be widely used in geographic information systems, due to the recent progress in remote sensing technology such as laser altimeter systems, SAR and high-resolution satellite sensors. However, these complex TDTMs contain an enormous amount of data, making it is expensive to store, display, distribute (transmit) and analyze such models. In this paper, an adaptive level-of-detail (LOD) control method using wavelet-based multiresolution representation of the TDTM for the purpose of efficient data processing for transmitting and displaying a TDTM in a network-based server-client system is proposed. A TDTM consisting of both a DEM represented as a triangulated mesh and an STM represented as a digital image is used. Finally, some examples of proposed method are presented and the improvement in speed of model rendering and reduction in the amount of data using the proposed method were quantitatively evaluated. Hiroaki Date, Satoshi Kanai and Takeshi Kishinami, An Adaptive LOD Control Method for Textured Digital Terrain Model using Wavelet based Multiresolution Representation, Proceedings of IEEE 2001 International Geoscience and Remote Sensing Symposium, 4, 1847-1849 (2001), uniform (avi, 15MB), threshold (avi, 16MB), ROI (avi, 15MB) |
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WAVELET-BASED MULTIRESOLUTION REPRESENTATION OF A GEOMETRIC MODEL FOR FREE-FORM SURFACE MACHINING In a 3D free-form CAM system, a series of intermediate shape models for machining are required as the references of NC programming. The safety and efficiency of the machining greatly depend on the geometric relation between these intermediate shape models. However current CAM systems lack the function of automatic generation of the appropriate series of these shape models. In this paper, a new wavelet-based multiresolution representation (MRR) of a series of intermediate shape models for machining is proposed. The proposed MRR enables very compact data representation for these models. In this MRR, geometric relations between each resolution model can be controlled so as to avoid overcut and to level the cutting loads. Two new control methods for MRR based on the lifting scheme and wavelet coefficient modification are proposed to support the contour line and scan line milling. The effectiveness of the MRR was verified through simulation. Hiroaki Date, Satoshi Kanai and Takeshi Kishinami, Wavelet-based Multi-resolution Representation of a Geometric Model for Free-form Surface Machining, Proceedings of 2000 U.S.A.-JAPAN Symposium on Flexible Automation, 2, 1137-1144 (2000) (Best Paper Award) pdf |
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DIGITAL WATERMARKING FOR 3D POLYGONAL MODEL BASED ON WAVELET TRANSFORM Recently, much interest is being taken in method to protect the copyright of digital data and preventing illegal duplication of it. However, in the area of CAD/CAM and CG, there are no effective ways to protect the copyright of the 3D geometric models. As a first step to solve the problem, a new digital watermarking method for 3D polygonal models is introduced in this paper. Watermarking is one of the copyright protection methods where an invisible watermark is secretly embedded into the original data. The proposed watermarking method is based on the wavelet transform (WT) for the polygonal model. The watermark can be embedded in the large wavelet coefficient vectors at various resolution levels of the transformed model. The method makes the embedded watermark imperceptible and invariant to the affine transformation. And also makes the control of the geometric error caused by the watermarking reliable. Finally, the effectiveness of the proposed watermarking method is shown through several simulation results. Hiroaki Date, Satoshi Kanai and Takeshi Kishinami, Digital Watermarking for 3D Polygonal Model based on Wavelet Transform, Proceedings of DETCf99, 1999 ASME Design Engineering Technical Conferences, DETC/CIE-9031 (1999) pdf |