John William Branch

Automatic Hole-Filling of Triangular Meshes Using Local Radial Basis Function

Creating models of real objects is a complex task for which the use of traditional modeling techniques has proven to be difficult. To solve some of these problems, laser rangefinders are frequently used to sample an objects surface from several viewpoints resulting in a set of range images that are registered and integrated into a final triangulated model. In practice, due to surface reflectance properties, occlusions and accessibility limitations, certain areas of the objects surface are usually not sampled, leaving holes which create undesirable artifacts in the integrated model. In this paper, we present a novel algorithm for the automatic hole-filling of triangulated models. The algorithm starts by locating hole boundary regions. A hole consists of a closed path of edges of boundary triangles that have at least an edge, which is not shared with any other triangle. The edge of the hole is then fitted with a b-spline where the average variation of the torsion of the b-spline approximation is calculated. Using a simple threshold of the average variation of the torsion along the edge, one can automatically classify real holes from man-made holes. Following this classification process, we then use an automated version of a radial basis function interpolator to fill the inside of the hole using neighboring edges. Excellent experimental results are presented.

A Hole-Filling Algorithm for Triangular Meshes Using Local Radial Basis Function

Creating models of real objects is a complex task for which the use of traditional modeling techniques has proven to be difficult. To solve some of the problem encountered, laser rangefinders are frequently used to sample an object ́s surface from several viewpoints resulting in a set of range images that are registered and integrated into a final triangulated model. In practice, due to surface reflectance properties, occlusions and accessibility limitations, certain areas of the object ́s surface are not sampled leaving holes which create undesirable artifacts in the integrated model. In this paper, we present a novel algorithm for the automatic hole–filling of triangulated models. The algorithm starts by locating hole boundary regions. A hole consists of a closed path of edges of boundary triangles that have at least an edge, which is not shared with any other triangle. The edge of the hole is then fitted with a b-spline where the average variation of the torsion of the b-spline approximation is calculated. Using a simple threshold of the average variation of the torsion along the edge, one can automatically classify real holes from man-made holes. Following this classification process, we then use an automated version of a radial basis function interpolator to fill the inside of the hole using neighboring edges. Excellent experimental results are presented. 412 J. Branch et al.

Simple Method for Constructing NURBS Surfaces from Unorganized Points

In this paper, a new method for constructing NURBS surfaces from scattered and unorganized points is presented. The method is easy to implement and allows fitting a NURBS surface to a scattered point cloud without constructing either NURBS patches networks or polygon meshes. Based on the projection of the points onto the regression plane of the cloud, the method detects both regions where the cloud lacks points, and regions where the cloud is too dense. Then, by inserting and removing points, the point cloud is regularized and approximated by a NURBS surface. In order to reduce the approximation error, an evolutionary strategy obtains the weights of the NURBS surface so that the distance between the point cloud and the NURBS is minimal. Finally, the points inserted outside the bounds of the point cloud are removed by trimming the NURBS surface. Numerical and graphical results are provided, demonstrating that the method produces valid surfaces with low fitting error.

Automatic extraction of a quadrilateral network of NURBS patches from range data using evolutionary strategies

We propose an algorithm to produce automatically a 3-D CAD model from a set of range data, based on non-uniform rational B-splines (NURBS) surface fitting technique. Our goal is to construct automatically continuous geometric models, assuming that the topology of the surface is unknown. In the propose algorithm, the triangulated surface is partitioned in quadrilateral patches, using Morse theory. The quadrilateral regions on the mesh are then regularized using geodesic curves and B-splines to obtain an improved smooth network on which to fit NURBS surfaces. NURBS surfaces are fitted and optimized using evolutionary strategies. In addition, the patches are smoothly joined guaranteeing C1 continuity. Experimental results are presented.

Automated Reverse Engineering of Free Form Objects Using Morse Theory

In this paper, a method for surface reconstruction by means of optimized NURBS (non-uniform rational b-splines) patches from complex quadrilateral bases on triangulated surfaces of arbitrary topology is proposed. To decompose the triangulated surface into quadrilateral patches, Morse theory and spectral mesh analysis are used. The quadrilateral regions obtained from this analysis is then regularized by computing the geodesic curves between each corner of the quadrilateral regions. These geodesies are then fitted by a B-splines curves creating a quadrilateral network on which a NURBS surface is fitted. The NURBS surfaces are then optimized using evolutive strategies to guaranty the best fit as well as C1 continuity between the patches.

Stereo Correspondence Evaluation Methods: A Systematic Review

The stereo correspondence problem has received significant attention in literature during approximately three decades. During that period of time, the development on stereo matching algorithms has been quite considerable. In contrast, the proposals on evaluation methods for stereo matching algorithms are not so many. This is not trivial issue, since an objective assessment of algorithms is required not only to measure improvements on the area, but also to properly identify where the gaps really are, and consequently, guiding the research. In this paper, a systematic review on evaluation methods for stereo matching algorithms is presented. The contributions are not only on the found results, but also on how it is explained and presented: aiming to be useful for the researching community on visual computing, in which such systematic review process is not yet broadly adopted.

Toward an automatic hole characterization for surface correction

This paper describes a method for Automatic hole characterization on 3D meshes, avoiding user intervention to decide which regions of the surface should be corrected. The aim of the method is to classify real and false anomalies without user intervention by using a contours irregularity measure based on two geometrical estimations: the torsion contours estimation uncertainty, and an approximation of geometrical shape measure surrounding the hole.

Automatic Extraction of Quadrilateral Patches from Triangulated Surfaces Using Morse Theory

A method for decompose the triangulated surface into quadrilateral patches using Morse theory and Spectral mesh analysis is proposed. The quadrilateral regions extracted are then regularized by means of geodesic curves and fitted using a B-splines creating a new grid on which NURBS surfaces can be fitted.

Fitting Surface of Free Form Objects using Optimized NURBS Patches Network with Evolutionary Strategies (mu + lambda) - ES.

We propose an algorithm to produce a 3-D CAD model from a set of range data, based on non-uniform rational B-splines (NURBS) surface fitting technique. Our goal is to construct continuous geometric models, assuming that the topology of surface is unknown. In our approach, the triangulated surface is partitioned in quadrilateral patches, using Morse theory. The quadrilateral obtained mesh is regularized by means of the use of geodesic curves and B-splines to obtain a new adequate grid on which to draw NURBS surfaces. Such NURBS surfaces are optimized by means of evolutionary strategies. Further, the patches are smoothly joined guaranteeing continuity C 1 .

A Robust Method for Registration of Partially-Overlapped Range Images Using Genetic Algorithms

Registration is a fundamental stage in the 3–D reconstruction process. We consider the problem of Euclidean alignment of two arbitrarily-oriented, partially-overlapped surfaces represented by measured point sets contaminated by noise and outliers. Given two approximately aligned range images of a real object, it is possible to carry out the registration of those images using numerous algorithms such as ICP. Basically the task is to match two or more images taken at different times, from different sensors, or from different viewpoints. In this paper, we discuss a number of possible approaches to the registration problem and propose a new method based on the manual pre-alignment of the range images of arbitrarily-oriented surfaces followed by an automatic registration process using a novel genetic optimization algorithm in 3–D data registration. Results for real range data are presented with precision and robustness, combined with the generality of genetic algorithms. This procedure focuses on the problem of obtaining the best correspondence between points through a robust search method between partially overlapped images.