Touch-based haptics for interactive editing on point set surfaces

A modeling paradigm for haptics-based editing on point set surfaces exploits implicit surfaces, physics-based modeling, point-sampled surfaces, and haptic. We propose a point-based geometry representation that we initially designed for dynamic physics-based sculpting, but can easily generalize to other relevant applications such as data modeling and human-computer interaction. By extending the idea of the local reference domain in the moving least square (MLS) surface model to the construction of a local and global surface distance field, we naturally incorporate Hua and Qin's dynamic implicit volumetric model into our deformation of the point-based geometry, which not only facilitates topology change but also affords dynamic sculpting and deformation.     

Triangulation of 3D surfaces

A simple generator of graded triangular meshes on spatial surfaces is introduced in this paper. The algorithm is based on the approximation of the surface by tensor product polynomial patches which are uniquely mappable on a planar parametric space. Each of the patches is triangulated separately in its parametric space, using modified advancing front technique allowing for generation of pre-stretched elements, and the obtained triangulation is mapped back onto the original surface. Large effort has been devoted to the treatment of singularities arising on surfaces approximated by degenerated patches.     

Simulation of ultrasound guided needle puncture using patient specific data with 3D textures and volume haptics

We present an integrated system for training ultrasound (US) guided needle puncture. Our aim is to provide a validated training tool for interventional radiology (IR) that uses actual patient data. IR procedures are highly reliant on the sense of touch and so haptic hardware is an important part of our solution. A hybrid surface/volume haptic rendering of an US transducer is proposed to constrain the device to remain outside the bony structures when scanning the patient's skin. A volume haptic model is proposed that implements an effective model of needle puncture. Force measurements have been made on real tissue and the resulting data is incorporated into the model. The other input data required is a computed tomography (CT) scan of the patient that is used to create the patient specific models. It is also the data source for a novel simulation of a virtual US scanner, which is used to guide the needle to the correct location. Copyright © 2007 John Wiley & Sons, Ltd.     

Determining pose of 3D objects with curved surfaces

A method is presented for computing the pose of rigid 3D objects with arbitrary curved surfaces. Given an input image and a candidate object model and aspect, the method will verify whether or not the object is present and if so, report pose parameters. The curvature method of Bash and Ullman is used to model points on the object rim, while stereo matching is used for internal edge points. The model allows an object edge-map to be predicted from pose parameters. Pose is computed via an iterative search for the best pose parameters. Heuristics are used so that matching can succeed in the presence of occlusion and artifact and without resetting to use of corresponding salient feature points. Bench tests and simulations show that the method almost always converges to ground truth pose parameters for a variety of objects and for a broad set of starting parameters in the same aspect     

Streaming 3D deforming surfaces with dynamic resolution control

Real‐time streaming of shape deformations in a shared distributed virtual environment is a challenging task due to the difficulty of transmitting large amounts of 3D animation data to multiple receiving parties at a high frame rate. In this paper, we present a framework for streaming 3D shape deformations, which allows shapes with multi‐resolutions to share the same deformations simultaneously in real time. The geometry and motion of deforming mesh or point‐sampled surfaces are compactly encoded, transmitted, and reconstructed using the spectra of the manifold harmonics. A receiver‐based multi‐resolution surface reconstruction approach is introduced, which allows deforming shapes to switch smoothly between continuous multi‐resolutions. On the basis of this dynamic reconstruction scheme, a frame rate control algorithm is further proposed to achieve rendering at interactive rates. We also demonstrate an efficient interpolation‐based strategy to reduce computing of deformation. The experiments conducted on both mesh and point‐sampled surfaces show that our approach achieves efficient performance even if deformations of complex 3D surfaces are streamed. Copyright © 2013 John Wiley & Sons, Ltd.     

Geometric segmentation of 3D scanned surfaces

The geometric segmentation of a discrete geometric model obtained by the scanning of real objects is affected by various problems that make the segmentation difficult to perform without uncertainties. Certain factors, such as point location noise (coming from the acquisition process) and the coarse representation of continuous surfaces due to triangular approximations, introduce ambiguity into the recognition process of the geometric shape. To overcome these problems, a new method for geometric point identification and surface segmentation is proposed.The point classification is based on a fuzzy parameterization using three shape indexes: the smoothness indicator, shape index and flatness index. A total of 11 fuzzy domain intervals have been identified and comprise sharp edges, defective zones and 10 different types of regular points. For each point of the discrete surface, the related membership functions are dynamically evaluated to be adapted to consider, point by point, those properties of the geometric model that affects uncertainty in point type attribution.The methodology has been verified in many test cases designed to represent critical conditions for any method in geometric recognition and has been compared with one of the most robust methods described in the related literature.     

Registration of 3D objects and surfaces

An approach to the problem of comparative analysis of objects and their surfaces that arises in medical imaging is presented and illustrated with an application to postsurgical bone-graft separation. A common requirement in medical imaging applications is the registration of multiple representations of the object prior to mensuration. The modeling of the registration process and the registration system are described. The measurement of change in volume of bone grafts implanted inside the human body in a corrective surgical procedure is discussed, and the results are evaluated     

On the meshing of trimmed 3D surfaces

A novel approach for generating quadrilateral meshes on trimmed three-dimensional surfaces is proposed. The parametric plane to Cartesian space mapping technique is extensively employed in this approach. Newly defined ‘separators’, are created on a given surface and nodes are generated on them. The relationship between nodes and separators, which is invariant in both the parametric plane and Cartesian space, is maintained for the ease of triangulation. Trimmed surfaces are discretized and the resulting meshes are presented to validate the proposed algorithm.     

三维重建效果评价技术综述

三维重建技术快速发展,并且在各个领域得到广泛应用。为比较各种重建方法的评价效果的优劣,现将其中一些方法进行比较分析,期望能够对该领域的发展状况全面了解,并且明确未来的研究方向。     

Image‐based modeling of 3D objects with curved surfaces

This paper addresses an image‐based method for modeling 3D objects with curved surfaces based on the non‐uniform rational B‐splines (NURBS) representation. The user fits the feature curves on a few calibrated images with 2D NURBS curves using the interactive user interface. Then, 3D NURBS curves are constructed by stereo reconstruction of the corresponding feature curves. Using these as building blocks, NURBS surfaces are reconstructed by the known surface building methods including bilinear surfaces, ruled surfaces, generalized cylinders, and surfaces of revolution. In addition to them, we also employ various advanced techniques, including skinned surfaces, swept surfaces, and boundary patches. Based on these surface modeling techniques, it is possible to build various types of 3D shape models with textured curved surfaces without much effort. Copyright © 2007 John Wiley & Sons, Ltd.     

断裂面匹配的破碎刚体复原

提出一种根据断裂面匹配进行破碎刚体复原的算法。首先根据积分不变量采用简单区域生长算法,将碎块表面以棱边为界限分割成多张曲面,根据法矢扰动区分出断裂面和原始面;然后根据断裂面顶点的平均积分不变量是否相近和邻域曲面是否相似,获得少量特征显著的相似点对,其中采用基于相容性约束的方法判断邻域曲面的相似性;之后采用引入三角形相似约束的穷举搜索的方法和投票机制进行断裂面的匹配;最后使用基于回溯的子图融合的方法进行碎块的整体拼合。实验结果表明,该算法能够对较复杂的碎块进行准确的拼接复原。     

Topology based 2D engineering drawing and 3D model matching for process plant

Process plant models mainly include 3D models and 2D engineering drawings. Matching calculation between these CAD models has wide applicability in model consistency check and retrieval. In process plant, engineering design standards make 2D engineering drawing and 3D model differ in geometry, proportion and structure, leading to the inapplicability of current shape-feature based matching approaches. Since connection relationships between components are the core of a process plant, a topology based algorithm is proposed. Firstly, by exploiting components as vertices and relationships as edges, both 2D engineering drawing and 3D model are preprocessed into graph structures. Then each model’s relationship types are extracted from the graph. Finally, regarding the extracted relationship types as primary feature, feature similarity is calculated to measure the matching degree between their corresponding models. The proposed algorithm is geometric deformation invariant. Experiments with industrial applications are presented, which demonstrates the effectiveness and feasibility of the proposed algorithm.     

2D representation of facial surfaces for multi-pose 3D face recognition

The increasing availability of 3D facial data offers the potential to overcome the intrinsic difficulties faced by conventional face recognition using 2D images. Instead of extending 2D recognition algorithms for 3D purpose, this letter proposes a novel strategy for 3D face recognition from the perspective of representing each 3D facial surface with a 2D attribute image and taking the advantage of the advances in 2D face recognition. In our approach, each 3D facial surface is mapped homeomorphically onto a 2D lattice, where the value at each site is an attribute that represents the local 3D geometrical or textural properties on the surface, therefore invariant to pose changes. This lattice is then interpolated to generate a 2D attribute image. 3D face recognition can be achieved by applying the traditional 2D face recognition techniques to obtained attribute images. In this study, we chose the pose invariant local mean curvature calculated at each vertex on the 3D facial surface to construct the 2D attribute image and adopted the eigenface algorithm for attribute image recognition. We compared our approach to state-of-the-art 3D face recognition algorithms in the FRGC (Version 2.0), GavabDB and NPU3D database. Our results show that the proposed approach has improved the robustness to head pose variation and can produce more accurate 3D multi-pose face recognition.     

Infrared system for 3D scanning of metallic surfaces

Many experimental techniques and many commercial solutions have been proposed to realize non-contact 3D digitization of industrial objects. Unfortunately, the performances of active 3D scanners depend on the optical properties of the surface to digitize. That is why the results obtained by active 3D triangulation on specular or transparent surfaces are not as good as those obtained on diffuse surfaces. In this paper, we present the developments we have realized to address highly reflective metallic surfaces. These developments are based on the extension of a technique, called “Scanning from heating” and initially dedicated to glass material. In comparison to conventional active triangulation techniques that measure the reflection of visible radiation, we measure here the thermal emission of a surface, which is locally heated by a laser source. We describe in this paper the successive steps we have followed to adapt Scanning From Heating to metallic materials, to evaluate the performances and finally to develop an operational prototype.     

Representation of 3D surfaces by two-variable Fourier descriptors

A method for generating two-variable 3D FDs directly from a striped lighting system is developed. An iterative algorithm is proposed to compute the two-variable 3D FDs for both axisymmetric and nonaxisymmetric objects and a formula for convergence test is derived. Experiments conducted for a set of 3D objects show that the iterative algorithm converges very quickly and the two-variable 3D FD representations are attained accurately     

Processing of 3D meshed surfaces using spherical wavelets

This paper presents an efficient technique for processing of 3D meshed surfaces via spherical wavelets.More specifically,an input 3D mesh is firstly transformed into a spherical vector signal by a fast low distortion spherical parameterization approach based on symmetry analysis of 3D meshes.This signal is then sampled on the sphere with the help of an adaptive sampling scheme.Finally,the sampled signal is transformed into the wavelet domain according to spherical wavelet transform where many 3D mesh processing operations can be implemented such as smoothing,enhancement,compression,and so on.Our main contribution lies in incorporating a fast low distortion spherical parameterization approach and an adaptive sampling scheme into the frame for processing 3D meshed surfaces by spherical wavelets,which can handle surfaces with complex shapes.A number of experimental examples demonstrate that our algorithm is robust and efficient.     

Skewed rotational symmetry detection from a 2D line drawing of a 3D polyhedral object

This paper introduces a new algorithm for detecting skewed rotational symmetry in a 2D line drawing of a 3D polyhedral object by locating the possibly-multiple symmetry axes. The drawing is converted into an edge–vertex graph from which the algorithm finds the faces of the object and the sets of topologically symmetric edges and vertices. It then checks that each set of vertices is rotationally symmetric geometrically by analyzing the distribution of the vertices around the circumference of the best-fit ellipse. The object is rotationally skewed symmetric if the best fit ellipses of all the vertex sets have parallel axes, equal ratio of major radius to minor radius and centers on the axis of rotation. A tolerance is used in the calculation to allow for inaccuracies in the line drawings. A set of experimental results is presented showing that the algorithm works well.     

Stable fitting of 2D curves and 3D surfaces by implicit polynomials

This work deals with fitting 2D and 3D implicit polynomials (IPs) to 2D curves and 3D surfaces, respectively. The zero-set of the polynomial is determined by the IP coefficients and describes the data. The polynomial fitting algorithms proposed in this paper aim at reducing the sensitivity of the polynomial to coefficient errors. Errors in coefficient values may be the result of numerical calculations, when solving the fitting problem or due to coefficient quantization. It is demonstrated that the effect of reducing this sensitivity also improves the fitting tightness and stability of the proposed two algorithms in fitting noisy data, as compared to existing algorithms like the well-known 3L and gradient-one algorithms. The development of the proposed algorithms is based on an analysis of the sensitivity of the zero-set to small coefficient changes and on minimizing a bound on the maximal error for one algorithm and minimizing the error variance for the second. Simulation results show that the proposed algorithms provide a significant reduction in fitting errors, particularly when fitting noisy data of complex shapes with high order polynomials, as compared to the performance obtained by the above mentioned existing algorithms.     

Approximating digital 3D shapes by rational Gaussian surfaces

A method for approximating spherical topology digital shapes by rational Gaussian (RaG) surfaces is presented. Points in a shape are parametrized by approximating the shape with a triangular mesh, determining parameter coordinates at mesh vertices, and finding parameter coordinates at shape points from interpolation of parameter coordinates at mesh vertices. Knowing the locations and parameter coordinates of the shape points, the control points of a RaG surface are determined to approximate the shape with a required accuracy. The process starts from a small set of control points and gradually increases the control points until the error between the surface and the digital shape reduces to a required tolerance. Both triangulation and surface approximation proceed from coarse to fine. Therefore, the method is particularly suitable for multiresolution creation and transmission of digital shapes over the Internet. Application of the proposed method in editing of 3D shapes is demonstrated.