Meshing 2D Shapes using Iso-lines of Radial Basis Functions

Yutaka Ohtake,Hiromasa Suzuki (사)한국CDE학회 2010 한국CAD/CAM학회 국제학술발표 논문집 Vol.2010 No.8

Outlier/Noise-Robust Partition of Unity Implicit Surface Reconstruction

Yukie Nagai,Yutaka Ohtake,Hiromasa Suzuki,Hideo Yokota (사)한국CDE학회 2010 한국CAD/CAM학회 국제학술발표 논문집 Vol.2010 No.8

In this paper, we propose an algorithm for outlier/noise-robust surface reconstruction based on a partition of unity (PU) approach. PU based surface reconstruction is a local method that covers an area including sampling points with spherical supports of local approximations, and then generates an approximation function whose zero-level sets approximate the surface. This algorithm has many advantages including representation of fine details, and fast and memory efficient computation. Many of these advantages are realized with the locality of PU however, it is also the reason of outlier/noise-instabilities. Unfortunately, scanned data generally contain much amount of noise, and hence improving the robustness of PU based algorithm is required. We achieve an outlier/noise-robust algorithm with integrating Graph-cut and diffusion of local approximations. Since the characteristics of outliers and noise are fundamentally different, overcoming these two with different approaches is reasonable. In our algorithm, first a spherical cover of an area containing input points is generated following the PU manner. And then Graph-cut is performed in order to determine spherical supports which are considered wrongly approximating affected by outliers. Finally, the PU approximation function is updated so that its gradient field smoothed. This smoothing is based on a diffusion of the local approximations. In this paper we show the effects of this integration approach for several scanned data sets.

Mesh processing for improved perceptual quality of 3D printed relief

Yifan Yang,Yutaka Ohtake,Hiromasa Suzuki 한국CDE학회 2021 Journal of computational design and engineering Vol.8 No.1

Making arts and crafts is an essential application of 3D printing. However, typically, 3D printers have limited resolution; thus, the perceptual quality of the result is always low, mainly when the input mesh is a relief. To address this problem using existing 3D printing technology, we only operate the shape of the input triangle mesh. To improve the perceptual quality of a 3D printed product, we propose an integrated mesh processing that comprises feature extraction, 3D print preview, feature preservation test, and shape enhancement. The proposed method can identify and enlarge features that need to be enhanced without large-scale deformation. Besides, to improve ease of use, intermediate processes are visualized via user interfaces. To evaluate the proposed method, the processed triangle meshes are 3D printed. The effectiveness of the proposed approach is confirmed by comparing photographs of the original 3D prints and the enhanced 3D prints.

3D scanning based mold correction for planar and cylindrical parts in aluminum die casting

Seno, Takashi,Ohtake, Yutaka,Kikuchi, Yuji,Saito, Noriaki,Suzuki, Hiromasa,Nagai, Yukie Society for Computational Design and Engineering 2015 Journal of computational design and engineering Vol.2 No.2

Aluminum die casting is an important manufacturing process for mechanical components. Die casting is known to be more accurate than other types of casting; however, post-machining is usually necessary to achieve the required accuracy. The goal of this investigation is to develop machining- free aluminum die casting. Improvement of the accuracy of planar and cylindrical parts is expected by correcting metal molds. In the proposed method, the shape of cast aluminum made with the initial metal molds is measured by 3D scanning. The 3D scan data includes information about deformations that occur during casting. Therefore, it is possible to estimate the deformation and correction amounts by comparing 3D scan data with product computer-aided design (CAD) data. We corrected planar and cylindrical parts of the CAD data for the mold. In addition, we corrected the planar part of the metal mold using the corrected mold data. The effectiveness of the proposed method is demonstrated by evaluating the accuracy improvement of the cast aluminum made with the corrected mold.

3D printing CFD simulation results using structural mechanics

Hiroki Takeda,Yutaka Ohtake,Hiromasa Suzuki 한국CDE학회 2020 Journal of computational design and engineering Vol.7 No.3

Good visualizations of computational fluid dynamics (CFD) results are key to making the best use of them. In many cases, CFD results involve multidimensional data embedded in 3D, and it can be difficult to recognize such complicated 3D shapes when they are projected onto 2D displays. A promising alternative approach uses a 3D printer to build real objects representing the CFD results. In this paper, we present a method of 3D printing the isosurfaces of CFD results to visualize them. However, there is a problem that the isosurfaces are not connected. Therefore, to prevent the structure from breaking up, we must find a way to connect them, and we achieve this by using beams to generate a support structure. We take a structural mechanics approach, using an algorithm to optimize the support structure such that the printed object does not break under gravity, enabling us to hold it safely for observation.

Flattening simulations of 3D thick sheets made of fiber composite materials

Morioka, Kotaro,Ohtake, Yutaka,Suzuki, Hiromasa,Nagai, Yukie,Hishida, Hiroyuki,Inagaki, Koichi,Nakamura, Takeshi,Watanabe, Fumiaki Society for Computational Design and Engineering 2015 Journal of computational design and engineering Vol.2 No.2

Recently, fiber composite materials have been attracting attention from industry because of their remarkable material characteristics, including light weight and high stiffness. However, the costs of products composed of fiber materials remain high because of the lack of effective manufacturing and designing technologies. To improve the relevant design technology, this paper proposes a novel simulation method for deforming fiber materials. Specifically, given a 3D model with constant thickness and known fiber orientation, the proposed method simulates the deformation of a model made of thick fiber-material. The method separates a 3D sheet model into two surfaces and then flattens these surfaces into two dimensional planes by a parameterization method with involves cross vector fields. The cross vector fields are generated by propagating the given fiber orientations specified at several important points on the 3D model. Integration of the cross vector fields gives parameterization with low-stretch and low-distortion.

Fitting CAD data to scanned data with large deformation

Shintaro Suzuki,Yutaka Ohtake,Hiromasa Suzuki 한국CDE학회 2020 Journal of computational design and engineering Vol.7 No.2

Recently, largely deformed simulation models, such as car crash simulations, have been in high demand. To evaluate such models, it is necessary to use actual deformation results to compare and validate them. When measuring actual deformed objects, an X-ray CT is useful because it is non-destructive. However, matching undeformed CAD data and scanned deformation data is difficult. We propose a system for users to set control points or control lines on feature points and predict deformation using affine transformation with the moving least squares method. In the proposed method, undesirable distortions are reduced by evaluating scaling using singular value index and introducing offset control points. The deformed CAD data are obtained by matching predicted CAD data and a polygon mesh generated by deformed CT data. In addition, the surface elements of the generated deformed CAD data are evaluated for CAE.

Mesh Generation of Porous Metals from X-ray Computed Tomography Volume Data

Zhenyu Niu,Hiromasa Suzuki,Yutaka Ohtake,Takashi Michikawa (사)한국CDE학회 2013 한국CAD/CAM학회 국제학술발표 논문집 Vol.2010 No.8

Recently, to meet the requirement of machine industry, there has been an increased focus on the development of porous metal as a high-strength material despite its low density. To evaluate its properties and quality, material testing is usually conducted. However, it is more efficient to perform computer simulation evaluations using finite element analysis. In fact, converting a large piece of porous metal into digitized mesh data is significantly difficult because of its complex inner structure. The X-ray computed tomography scanning technique enables us to obtain the information regarding the internal structure of the metal. Furthermore, a reconstruction algorithm produces volume data of the test object. In general, conventional methods are utilized to generate mesh data from volume data, but a key drawback is that they generate too many elements, resulting in high computational cost. We propose an approach to generate meshes for porous structures by modeling each pore using spheres from volume data. Data conversion is conducted through a series of processes namely labeling, spherical approximation, shape approximation, region segmentation, and meshing. The result verifies the feasibility of the proposed method, which generates shape-approximated and finite-element-simulation-available mesh data using fewer elements.

Mesh generation of porous metals from X-ray computed tomography volume data

Zhenyu Niu,Hiromasa Suzuki,Yutaka Ohtake,Takashi Michikawa 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.7

Recently, to meet the requirement of machine industry, there has been an increased focus on the development of porous metal as ahigh-strength material despite its low density. To evaluate its properties and quality, material testing is usually conducted. However, it ismore efficient to perform computer simulation evaluations using finite element analysis. The X-ray computed-tomography scanningtechnique enables us to obtain the information regarding the internal structure of the metal. Furthermore, a reconstruction algorithm producesvolume data of the test object. In general, conventional methods are utilized to generate mesh data from volume data for finiteelement analysis, but a key drawback is that they generate too many elements, resulting in high computational cost. We propose an approachto generate meshes for porous structures by modeling each pore using spheres from volume data.

Visualization of user’s attention on objects in 3D environment using only eye tracking glasses

Ting-Hao Li,Hiromasa Suzuki,Yutaka Ohtake 한국CDE학회 2020 Journal of computational design and engineering Vol.7 No.2

Eye tracking technology is widely applied to detect user’s attention in a 2D field, such as web page design, package design, and shooting games. However, because our surroundings primarily consist of 3D objects, applications will be expanded if there is an effective method to obtain and display user’s 3D gaze fixation. In this research, a methodology is proposed to demonstrate the user’s 3D gaze fixation on a digital model of a scene using only a pair of eye tracking glasses. The eye tracking glasses record user’s gaze data and scene video. Thus, using image-based 3D reconstruction, a 3D model of the scene can be reconstructed from the frame images; simultaneously, the transformation matrix of each frame image can be evaluated to find 3D gaze fixation on the 3D model. In addition, a method that demonstrates multiple users’ 3D gaze fixation on the same digital model is presented to analyze gaze distinction between different subjects. With this preliminary development, this approach shows potential to be applied to a larger environment and conduct a more reliable investigation.