609 Works

History Based Reactive Objects for Immersive CAD

T. Convard & P. Bourdot
Virtual Environments (VE) allow direct 3D interaction, better perception of shapes and a feel of immersion, properties that are highly desirable for design tasks. Traditional CAD software extensively use WIMP interfaces (Windows, Icons, Menus and Pointing device), but these interaction models are not suited in VE. Moreover, during a design task, the use of dialog boxes, buttons, etc. deteriorates the user's focus on his work. However, to fully bene t from immersive interaction we need...

Physics-based Modelling and Simulation of Functional Cloth for Virtual Prototyping Applications

M. Fontana, C. Rizzi & U. Cugini
A CAD-oriented system is proposed for the design of complex-shaped functional cloth, provided with a physics-based modelling core for simulation and virtual prototyping tasks. Textiles are physically modelled as particle grids in 3D space subjected to Newtonian dynamics, with internal spring, bending and shear forces derived from KES-F data measuring material behaviour. Interactions with the environment are expressed as external forces, collisions against obstacles, self-collisions and constraints. Differently from physicsbased animation systems, the proposed system...

Stability and Homotopy of a Subset of the Medial Axis

F. Chazal & A. Lieutier
Medial Axis is known to be unstable for non smooth objects. The Medial Axis has applications in image analysis and mathematical morphology, Solid Modeling, or domain decomposition for CAD to CAE (i.e. Finite Elements) models generation.

Tracing Surface Intersection with a Validated ODE System Solver

H. Mukundan, K. H. Ko, T. Maekawa, T. Sakkalis & N. M. Patrikalakis
This paper presents a robust method for tracing intersection curve segments between continuous rational parametric surfaces, typically rational polynomial parametric surface patches. The tracing procedure is based on a validated ordinary differential equation (ODE) system solver which can be applied, without substantial overhead, for transversal as well as tangential intersections. Application of the validated ODE solver in the context of eliminating the phenomenon of straying and looping is discussed. In addition, we develop a method...

Topological and Geometric Beautification of Reverse Engineered Geometric Models

F. C. Langbein, A. D. Marshall, R. R. Martin, B. I. Mills & C. H. Gao
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. Beauti cation 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 beauti cation system suitable for improving the...

Implicit Curve and Surface Design Using Smooth Unit Step Functions

Q. Li
This paper presents an implicit curve and surface design technique that uses smooth unit step functions. With the proposed method, an implicit curve or surface can be generated by inputting a sequence of points together with the normals at these points of the curve or surface to be designed. By choosing appropriate smooth unit step functions, these curves and surfaces can be designed to any required degree of smoothness.

Reconstruction with 3D Geometric Bilateral Filter

A. Miropolsky & A. Fischer
In recent years, reverse engineering (RE) techniques have been developed for surface reconstruction from 3D scanned data. Typical sampling data, however, usually is large scale and contains unorganized points, thus leading to some anomalies in the reconstructed object. To improve performance and reduce processing time, Hierarchical Space Decomposition (HSD) methods can be applied. These methods are based on reducing the sampled data by replacing a set of original points in each voxel by a representative...

Developability-preserved Free-form Deformation of Assembled Patches

C. C. L. Wang & K. Tang
A novel and practical approach is presented in this paper that solves a constrained free-form deformation (FFD) problem where the developability of the tessellated embedded surface patches is preserved during the lattice deformation. The formulated constrained FFD problem has direct application in areas of product design where the surface developability is required, such as clothing, ship hulls, automobile parts, etc. In the proposed approach, the developability-preserved FFD problem is formulated as a constrained optimization problem....

Constraint-based Design of B-spline Surfaces from Curves

P. Michalik & B. D. Bruderlin
In this paper we describe the design of B-spline surface models by means of curves and tangency conditions. The intended application is the conceptual constraint-driven design of surfaces from hand-sketched curves. The solving of generalized curve surface constraints means to find the control points of the surface from one or several curves, incident on the surface, and possibly additional tangency and smoothness conditions. This is accomplished by solving large, and generally under-constrained, and badly conditioned...

Making the Most of Using Depth Reasoning to Label Line Drawings of Engineering Objects

P. A. C. Varley, R. R. Martin & H. Suzuki
Automatic creation of B-rep models of engineering objects from freehand sketches would benefit designers. A subgoal is to take a single line drawing (with hidden lines removed), and from it deduce an initial 3D geometric realisation of the visible part of the object. Junction and line labels, and provisional depth coordinates, are important components of this frontal geometry. Most methods for producing frontal geometry use line labelling, but this takes little or no account of...

Progressive Dimension-Independent Boolean Operations

A. Paoluzzi, V. Pascucci & G. Scorzelli
This paper introduces a new progressive multi-resolution approach for representating and processing polyhedral objects of any dimension. Our representation, a variant of BSP trees [Nay90] combined with the Split scheme introduced in [BP96], allows progressive streaming and rendering of solid models at multiple levels of detail (LOD). Boolean set operations are computed progressively by reading in input a stream of incremental refinements of the operands. Each refinement of the input is mapped immediately to a...

Update Operations on 3D Simplicial Decompositions of Non-manifold Objects

L. De Floriani & A. Hui
We address the problem of updating non-manifold mixed-dimensional objects, described by three-dimensional simplicial complexes embedded in 3D Euclidean space. We consider two local update operations, edge collapse and vertex split, which are the most common operations performed for simplifying a simplicial complex. We examine the effect of such operations on a 3D simplicial complex, and we describe algorithms for edge collapse and vertex split on a compact representation of a 3D simplicial complex, that we...

Optimization Techniques for Approximation with Subdivision Surfaces

M. Marinov & L. Kobbelt
We present a method for scattered data approximation with subdivision surfaces which actually uses the true representation of the limit surface as a linear combination of smooth basis functions associated with the control vertices. This is unlike previous techniques which used only piecewise linear approximations of the limit surface. By this we can assign arbitrary parameterizations to the given sample points, including those generated by parameter correction. We present a robust and fast algorithm for...

An Effective Condition for Sampling Surfaces with Guarantees

J. D. Boissonnat & S. Oudot
The notion of e-sample, as introduced by Amenta and Bern, has proven to be a key concept in the theory of sampled surfaces. Of particular interest is the fact that, if E is an e-sample of a smooth surface S for a suf ciently small e, then the Delaunay triangulation of E restricted to S is a good approximation of S, both in a topological and in a geometric sense. Hence, if one can construct...

Tolerance Envelopes of Planar Parametric Part Models

Y. Ostrovsky-Berman & L. Joskowicz
We present a framework for the systematic study of parametric variation in planar mechanical parts and for ef ciently computing approximations of their tolerance envelopes. Part features are speci ed by explicit functions de ning their position and shape as a function of parameters whose nominal values vary along tolerance intervals. Their tolerance envelopes model perfect form Least and Most Material Conditions (LMC/MMC). Tolerance envelopes are useful in many design tasks such as quantifying functional...

B-rep SE: Simplicially Enhanced Boundary Representation

M. Freytag & V. Shapiro
Boundary representation (B-rep) is a popular representation scheme for mechanical objects due to its ability to accurately represent piecewise smooth surfaces bounding solids. However, non-trivial topology and geometry of the surface patches hinder point generation, classification, searching, and other algorithms. We propose a new hybrid representation that addresses these shortcomings by imposing on the boundary representation an additional simplicial structure. The simplicial structure applies a triangle-mesh metaphor to the usual boundary representation, allowing access to...

A Condition for Isotopic Approximation

F. Chazal & D. Cohen-Steiner
In this paper, we give a very simple and purely topological condition for two surfaces to be isotopic. This work is motivated by the problem of surface approximation. Applications to implicit surfaces are given, as well as connections with the well-known concepts of medial axis and local feature size.

Automatic Building of Structured Geological Models

S. Brandel, S. Schneider, , M. Perrin , N. Guiard, J. F. Rainaud, , P. Lienhardt & Y. Bertrand
The present article proposes a method to signi cantly improve the construction and updating of 3D geological models used for oil and gas exploration. The proposed method takes advantage of the speci c structures which characterize geological objects. We present a prototype of a “geological pilot” which enables monitoring the automatic building of a 3D model topologically and geologically consistent, starting from a set of unsegmented surfaces. The geological pilot uses a “Geological Evolution Scheme”...

Planar Parameterization for Closed Manifolds Genus-1 Meshes

D. Steiner & A. Fischer
Parameterization of 3D meshes is important for many graphics and CAD applications, in particular for texture mapping, re-meshing and morphing. Current parameterization methods for closed manifold genus-n meshes usually involve cutting the mesh according to the object generators, fixing the resulting boundary and then applying the 2D position for each of the mesh vertices on a plane, such that the flattened triangles are not too distorted and do not overlap. Unfortunately, fixing the boundary distorts...

Medial-Axis Based Solid Representation

A. Shaham, A. Shamir & D. Cohen-Or
The medial axis (MA) of an object and medial axis transform (MAT) have many applications in solid modeling, computer graphics and other areas. Exact computation of MA is complex and various medial axis approximation algorithms were studied. One of the most successful is based on the computation of the Voronoi diagram of a set of sample points on the boundary of the object. Based on this method we present a novel representation of solids, which...

From Computer Geometry to Manufacturing Algorithms

E. Cohen
Abstractly, machining a shape is rather a simple task, that is, one is merely asked to subtractively metamorphose a superset of stock material into the ultimate shape of a given geometric model. In practice, however, there are a multitude of technical considerations that make automating this process rather a formidable and generally unsolved problem.This presentation will discuss some of the practical and technical considerations of machining a desired shape from a block of stock material....

Multiresolution Heterogeneous Solid Modeling and Visualization Using Trivariate Simplex Splines

J. Hua, Y. He & H. Qin
This paper presents a new and powerful heterogeneous solid modeling paradigm for representing, modeling, and rendering of multi-dimensional, physical attributes across any volumetric objects. The modeled solid can be of complicated geometry and arbitrary topology. It is formulated using a trivariate simplex spline defined over a tetrahedral decomposition of any 3D domain. Heterogeneous material attributes associated with solid geometry can be modeled and edited by manipulating the control vectors and/or associated knots of trivariate simplex...

Efficient and Robust Computation of an Approximated Medial Axis

Y. Yang, O. Brock & R. N. Moll
The medial axis can be viewed as a compact representation for an arbitrary model; it is an essential geometric structure in many applications. A number of practical algorithms for its computation have been aimed at speeding up its computation and at addressing its instabilities. In this paper we propose a new algorithm to compute the medial axis with arbitrary precision. It exhibits several desirable properties not previously combined in a practical and ef cient algorithm....

Residual Iteration and Accurate Polynomial Evaluation for Shape-interrogation Applications

C. Hoffmann, With G. Park, J-R. Simard & N. F. Stewart
Surface interrogation and intersection depend crucially on good root-finding algorithms, which in turn depend on accurate polynomial evaluation. Conventional algorithms for evaluation typically encounter difficulties near multiple roots, or roots that are very close, and this may lead to gross errors in the geometric computation, or even catastrophic failure. In this paper we study the cost and accuracy of several approaches to polynomial evaluation, explaining the reasons for non-convergence of certain methods, and supporting our...

Registration Year

  • 2016