langbein's frankclangbein [36 articles]

Abstract

This paper analyses the noise present in range data measured by a Konica Minolta Vivid 910 scanner, in order to better characterise real scanner noise. Methods for denoising 3D mesh data have often assumed the noise to be Gaussian, and independently distributed at each mesh point. We show via measurements of an accurately machined almost planar test surface that real scanner data does not have such properties: the errors are not quite Gaussian, and more importantly, exhibit significant short range correlation. ...

Abstract

This paper considers an approach to mesh denoising based on the concept of random walks. The proposed method consists of two stages: a face normal filtering procedure, followed by a vertex position updating procedure which integrates the denoised face normals in a least-squares sense. Face normal filtering is performed by weighted averaging of normals in a neighbourhood. The weights are based on the probability of arriving at a given neighbour after a random walk of a virtual particle starting at a ...

Abstract

We present a simple and fast mesh denoising method, which can remove noise effectively while preserving mesh features such as sharp edges and corners. The method consists of two stages. First, noisy face normals are filtered iteratively by weighted averaging of neighboring face normals. Second, vertex positions are iteratively updated to agree with the denoised face normals. The weight function used during normal filtering is much simpler than that used in previous similar approaches, being simply a trimmed quadratic. This makes ...

Abstract

This paper discusses noise in range data measured by a Konica Minolta Vivid 910 scanner. Previous papers considering denoising 3D mesh data have often used artificial data comprising Gaussian noise, which is independently distributed at each mesh point. Measurements of an accurately machined, almost planar test surface indicate that real scanner data does not have such properties. An initial characterisation of real scanner noise for this test surface shows that the errors are not quite Gaussian, and more importantly, exhibit significant ...

Abstract

An approach to mesh denoising based on the concept of random walks is examined. The proposed method consists of two stages: face normal filtering, followed by vertex position updating to integrate the denoised face normals in a least-squares manner. Face normal filtering is performed by weighted averaging of normals in a neighbourhood. A novel approach to determining weights is to compute the probability of arriving at each neighbour following a fixed-length random walk of a virtual particle starting at a given ...

Abstract

An algorithm is presented to generate bas-reliefs based on adaptive histogram equalisation (AHE). The input may be either a 3D mesh model or a height field. If a mesh model is provided, a height field is first created via orthogonal or perspective projection. The height field is regularly gridded and treated as an image to generate the bas-relief using a modified AHE method, giving a bas-relief with a user-chosen height range. We modify the original image contrast enhancement AHE method to ...

Abstract

This paper analyses the noise present in range data measured by a Konica Minolta Vivid 910 scanner in order to better characterise real scanner noise. Methods for denoising 3D mesh data have often assumed the noise to be Gaussian, and independently distributed at each mesh point, when generating artificial test data for evaluating such methods. We show via measurements of an accurately machined, almost planar test surface that real scanner data does not have such properties: the errors are not quite ...

Abstract

Low-discrepancy point distributions exhibit excellent uniformity properties for sampling in applications such as rendering and measurement. We present an algorithm for generating low-discrepancy point distributions on arbitrary parametric surfaces using the idea of converting the 2D sampling problem into a 1D problem by adaptively mapping a space-filling curve onto the surface. The 1D distribution takes into account the parametric mapping by employing a corrective approach similar to histogram equalisation to ensure that it gives a 2D low-discrepancy point distribution on the ...

Abstract

A novel point sampling framework for polygonal meshes is presented, based on sampling a mesh according to a density-controlled low-discrepancy distribution. The local sampling density can be controlled by a density functional defined by the user, e.g. to preserve local features, or to achieve desired data reduction rates. To sample the mesh, it is cut into a disc topology, and a parametrisation is generated. The parameterised mesh is sampled using a Hilbert curve in the parameter domain, which is adapted to ...

Abstract

The authors are investigating reverse engineering for reconstructing the shape of simple mechanical parts. Currently, preliminary B-rep models can be created by fitting surfaces to point clouds obtained by scanning an actual part using a 3D laser scanner. The resulting model, although valid, is often not suitable for purposes such as redesign. This is because expected regularities and constraints are not present in the model. This report describes a number of aspects of the geometry of mechanical parts which should be ...

Abstract

The authors are developing an automated reverse engineering system for reconstructing the shape of simple mechanical parts. B-rep models are created by fitting surfaces to point clouds obtained by scanning an object using a 3D laser scanner. The resulting models, although valid, are often not suitable for purposes such as redesign because expected regularities and constraints are not present. This information is lost because each face of the model is determined independently. A global approach is required, in particular one that ...

Abstract

Various industrial applications require point sets that cover arbitrarily shaped surfaces of 3D objects. The nature of the sampling required depends on the application; while common machining or inspection processes need regularly arranged points for smooth path generation, the application described in this paper requires a more subtle distribution to provide a high-quality result. We contrast two sampling algorithms developed to support a novel, contactless robotic painting system which creates images on surfaces by selectively exposing a photographic coating using a ...

Abstract

Sculptural reliefs are widely used in various industries for purposes such as applying brands to packaging and decorating porcelain. In order to easily apply reliefs to CAD models, it is often desirable to reverse-engineer previously designed and manufactured reliefs. 3D scanners can generate triangle meshes from objects with reliefs; however, previous mesh segmentation work has not considered the particular problem of separation of reliefs from background. We consider here the specific case of segmenting a simple relief delimited by a single ...

Abstract

Reverse engineering of reliefs aims to turn an existing relief superimposed on an underlying surface into a geometric model which may be applied to a different base surface. Steps in this process include segmenting the relief from the background, and describing it as an offset height field relative to the underlying surface. We have previously considered relief segmentation using a geometric snake. Here, we show how to use this initial segmentation to estimate the background surface lying under the relief, which ...

Abstract

Segmentation of geometric reliefs from a textured background has various applications in reverse engineering. We consider two approaches to solve this problem. The first classifies parts of a surface mesh as relief or background, and then uses a snake which moves inwards towards the desired relief boundary, which is coarsely located using an energy based on the classification. The second approach initially smoothes the surface to eliminate the background texture, and locates the snake at the relief boundary using an energy ...

Abstract

Decorative reliefs are widely used for e.g. packaging and porcelain design. In periodic reliefs, the relief repeats a pattern, for example all the way around an underlying surface of revolution. Reverse engineering of existing reliefs allows them to be re-applied to different base surfaces; we show here how to segment a single repeat unit of a periodic relief starting from a scanned triangle mesh. We first briefly review how we segment the relief from the background surface using our previous work. ...

Abstract

This paper considers the mold design problem of computing a parting line for a complex mesh model, given a parting direction. Existing parting line algorithms are unsuitable for this case, as local variations in the orientations of the facets of such models lead to a parting line which zig-zags across the surface in an undesirable way. This paper presents a method to compute a smooth parting line which runs through a triangle band composed of triangles whose normals are approximately perpendicular ...

Abstract

We consider the problem of computing a parting line for a mold for a complex mesh model, given a parting direction, and the related problem of removing small undercuts, either pre-existing, or resulting from the parting line. Existing parting line algorithms are unsuitable for use with complex meshes: the faceted nature of such models leads to a parting line which zig-zags or wanders across the surface undesirably. Our method computes a smooth parting line which runs through a band of triangles ...

Abstract

Motivated by the need to detect design intent in approximate boundary representation models, we give an algorithm to detect incomplete symmetries of discrete points, giving the models’ potential local symmetries at various automatically detected tolerances. Here, incomplete symmetry is defined as a set of incomplete cycles which are constructed by, e.g., a set of consecutive vertices of an approximately regular polygon, induced by a single isometry. All seven 3D elementary isometries are considered for symmetry detection. Incomplete cycles are first found ...

Abstract

Detecting approximate symmetries of parts of a model is important when attempting to determine the geometrical design intent of approximate boundary-representation (B-rep) solid models produced e.g. by reverse engineering systems. For example, such detected symmetries may be enforced exactly on the model to improve its shape, to simplify its analysis, or to constrain it during editing. We give an algorithm to detect local approximate symmetries in a discrete point set derived from a B-rep model: the output comprises the model’s potential ...

Abstract

Finding design intent embodied as high-level geometric relations between a CAD model's sub-parts facilitates various tasks such as model editing and analysis. This is especially important for boundary-representation models arising from e.g. reverse engineering or CAD data transfer. These lack explicit information about design intent, and often, the intended geometric relations are only approximately present. We give a novel solution to this problem based on detecting approximate local incomplete symmetries, in a hierarchical decomposition of the model into simpler, more symmetric ...

Abstract

Approximate geometric models, e.g. as created by reverse engineering, describe the approximate shape of an object, but do not record the underlying design intent. Automatically inferring geometric aspects of the design intent, represented by feature trees and geometric constraints, enhances the utility of such models for downstream tasks. One approach to design intent detection in such models is to decompose them into regularity features. Geometric regularities such as symmetries may then be sought in each regularity feature, and subsequently be combined ...

Abstract

This document describes the PIDS algorithm and its application. PIDS is an algorithm to simplify expressions which are given as nested lists. The simplification is done by a set of rules which can be applied to the expressions. However the rules just describe how the expression can be rewritten, the real simplification is driven by a merit function. The purpose of PIDS is to simplify mathematical expressions. There might be other applications, though. In this article we just give a few ...

Abstract

Current reverse engineering systems are able to generate simple valid boundary representation (B-rep) models from 3D range data. Such models suffer from various inaccuracies caused by noise in the input data and algorithms. Reverse engineered geometric models may be beautified by finding approximate geometric regularities in such a model, and imposing a suitable subset of them on the model by using constraints. Methods to detect suitable regularities for the beautification of B-rep models having only planar, spherical, cylindrical, conical and toroidal ...

Abstract

Current reverse engineering systems can generate boundary representation (B-rep) models from 3D range data. Such models suffer from inaccuracies caused by noise in the input data and algorithms. The quality of reverse engineered geometric models can be improved by finding candidate shape regularities in such a model, and constraining the model to meet a suitable subset of them, in a post-processing step called beautification. This paper discusses algorithms to detect such approximate regularities in terms of similarities between feature objects describing ...

Abstract

Boundary representation models reconstructed from range data sufferfrom various inaccuracies caused by noise in the data and the model building software. The quality of such models can be improved in a beautfication step, which finds regular geometric patterns approximately present in the model and imposes a maximal consistent subset of constraints deducedfrom these patterns on the model. This pa per presents analysis methods seeking geometric patterns defined by similarities. Their specific types are derived from a part survey estimating the frequencies ...

Abstract

Current reverse engineering systems are able to generate simple valid boundary representation (B-rep) models from 3D range data. Such models suffer from various inaccuracies caused by noise in the input data and algorithms. The quality of reverse engineered geometric models can potentially be improved by finding candidate shape regularities in such an initial model, and imposing a suitable subset of them on the model by using constraints, in a postprocessing step called beautification. Finding such candidate regularities is a necessary first ...

Abstract

Boundary representation models reconstructed from 3D range data suffer from various inaccuracies caused by noise in the data and the model building software. Such models can be improved in a beautification step, which finds geometric regularities approximately present in the model and imposes a consistent subset of them on the model. Methods to select regularities consistently such that they are likely to represent the original, ideal design intent are presented. Efficiency during selection is achieved by considering degrees of freedom to ...

Abstract

Boundary representation models reconstructed from 3D range data suffer from various inaccuracies caused by noise in the data and the model building software. The quality of such models can be improved in a beautification step, which finds geometric regularities approximately present in the model and tries to impose a consistent subset of these reg- ularities on the model. A framework for beautification and numerical methods to select and solve a consistent set of constraints deduced from a set of regularities are ...

Abstract

In [2] we presented an algorithm for decomposing a boundary representation model hierarchically into regularity features by recovering broken symmetries. The algorithm adds new recoverable edges and faces, which can be constructed from existing geometry. This generates positive and negative volumes giving simple, more symmetric sub-parts of the model. The resulting regularity feature tree may be utilised for regularity detection to describe a model’s design intent in terms of regularities such as symmetries and congruencies. ...

Abstract

Boundary representation models reverse engineered from 3D range data suffer from various inaccuracies caused by noise in the measured data and the model building software. Beautification aims to improve such models in a post-processing step solely working with the boundary representation model. The improved model should exhibit topological and geometric regularities representing the original, ideal design intent. This paper gives an overview of algorithms for a complete beautification system suitable for improving the topology and the geometry of low to medium ...

Note (first note only)

Abstract

Boundary representation models reverse engineered from three-dimensional range data suffer from various inaccuracies caused by noise in the data and the model building software. Beautification aims to improve such models so that they exhibit exact geometric regularities representing the original, ideal design intent. In this thesis an approach to beautification as a post-processing step solely working with the boundary representation is investigated. Geometric regularities approximately present in the model are detected and a consistent subset of these regularities is imposed on ...

Abstract

Boundary representation models reconstructed from 3D range data suffer from various inaccuracies caused by noise in the data and by numerical errors in the model building software. The quality of such models can be improved in a beautification step, where geometric regularities need to be detected and imposed on the model, and defects requiring topological change need to be corrected. This paper considers changes to the topology such as the removal of short edges, small faces and sliver faces, filling of ...

Abstract

Reverse engineering allows the geometric reconstruction of simple mechanical parts. However, the resulting models suffer from inaccuracies caused by errors in measurement and reconstruction so such models do not have the exact congruences, symmetries and other regularities the original designer intended. We wish to impose such regularities in a beautification process. This paper discusses the particular problem of detecting approximate congruences between parts (e.g. a pair of handles) of a reconstructed B-rep model, so that a subsequent step can enforce them ...

Abstract

Engineering geometric models are often designed to have symmetries and other regularities. In knowledge based reuse, creative design and design for mass customization, to have the information of such symmetries and other regularities from a geometric model is very useful. And this can make us understand more about the geometric model. In reverse engineering, B-rep models are created by fitting surfaces from point sets obtained by scanning an object using a 3D laser scanner. Each fitted surface is determined independently. The ...