Papers by Keyword: Shape Reconstruction

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Authors: Qian Ma
Abstract: In this paper, we propose an improved method for reconstruct 3D facial shape from a single frontal image. We use improved fast marching method to solve the Eikonal equation which can obtained from the method of shape from shading (SFS). In order to overcome the concave-convex ambiguity problems inherent to SFS, we find out the concave region and recover concave into the convex keeping the relative shape invariant to reconstruct the accuracy facial shape.
Authors: M. Kitahara, M. Onishi, Kouichi Nakahata, Masayoshi Yamada
Abstract: The Born inverse scattering method is applied to the shape reconstruction of flaws in the concrete materials. To accelerate the inversion process, the algorithm of the fast Fourier transform is introduced in the integration process of the scattering amplitude. The concrete specimens with flaw models are prepared and the scattered waveforms from flaws are acquired in the pulse-echo mode. The shape of flaws is reconstructed by using the measured waveforms and the performance of the inversion method is demonstrated experimentally.
Authors: Yu Liu
Abstract: This paper constructs PSSs (Point Set Surfaces) by combining locally fitted quadric polynomials. First, an energy function is defined as the weighted sum of distances from a point to these quadric polynomials. Then, a vector field is constructed by the weighted sum of normal vectors at input points. Finally, points on a PSS are obtained by finding local minima of the energy function along the vector field. Experiments demonstrate that high quality PSSs can be obtained from the method presented for input point clouds sampled from various shapes.
Authors: Hiroshi Masuda, Ryo Matsuoka, Yuji Abe
Abstract: Engineering facilities can be digitized as large-scale point-clouds by using the state-of-art mid-range laser scanners. For utilizing captured data in CAD systems, it is important to convert point-clouds to parametric surfaces. In this paper, we describe a method for robustly extract cylindrical faces and planar faces. Edges and silhouette lines have to be generated to construct bounded faces, but unfortunately points on silhouettes are very noisy in the case of mid-range laser scanners. Our method applies region-growing method on spherical space and improves the robustness. In addition, we enhance the region-growing so that surface regions can be propagated to disconnect points using multiple overlapping point-clouds.
Authors: Gang Feng Zheng, Bin Wu, Cun Fu He
Abstract: In this article, three dimensional Born inverse scattering method is modified to convenient form to reconstruct the shape of a three-dimensional flaw in an inhomogeneous cylindrical specimen. In this modified method, a measurement plane is restricted to the plane perpendicular to the axis of the inhomogeneous cylindrical specimen. Thus the cross-sectional image of the flaw can be obtained. By moving the measurement plane along the axis of the inhomogeneous cylindrical specimen, the cross-sectional image is obtained for each measurement plane. The three-dimensional flaw image is reconstructed by piling up the obtained cross-sectional images. Inhomogeneous cylindrical specimen with an eccentric circular cylindrical cavity model is prepared. The performance of the modified method to reconstruct the three-dimensional flaw is verified by using the experimentally measured waveforms. From the experimental research for the eccentric circular cylindrical defect, it is verified that the modified Born inversion works well for the volume type defect.
Authors: Chia Hsiang Wu, Mei Yun Su
Abstract: Endoscopy provides a convenient way to access the inner structures of various organs. The endoscopic images provide an immediate observation and help diagnosis and therapy. Shape reconstruction from endoscopic images further provides real scale factor for image-guided navigation. However, specular highlights, bright patches of light appearing on the imaged surface, mask the real image texture and result in erroneous reconstruction. Therefore, the detection of specular highlights is essential for accurate reconstruction. In this study, we divide the images into homogeneous regions by color quantization and spatial segmentation. Then, a thresholding technique based on histogram of the pixel intensity values is used. Finally, we check the gray level consistency for each region to avoid over segmentation. The experimental results show that the proposed method can achieve successfully detection.
Authors: Gang Feng Zheng, Bin Wu, Cun Fu He
Abstract: It is well known that the Born approximation technique is highly effective under weak scattering conditions. In the paper, a cement paste cylindrical specimen with complex flaw is prepared and ultrasonic measurements are carried out by experimental means. The measurement area is restricted in the plane perpendicular to the axis of cylindrical specimen. The measured wave data are fed into the approximate technique formula—the inversion method and cross-sectional image is obtained. We find that good results have been obtained for strong scattering void flaws such as complex flaw in cement paste cylindrical specimen
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