Surface collision detection for virtual prototyping

This paper presents an efficient collision detection algorithm designed to support assembly and maintenance simulation of complex assemblies. This approach exploits the surface knowledge, available from CAD models, to determine intersecting surfaces. It proposes a novel combination of Overlapping Axis-Aligned Bounding Box (OAABB) and R-tree structures to gain considerable performance improvements. This paper also shows an efficient traversal algorithm based on the R-tree structure of Axis-Aligned Bounding Boxes to determine intersecting objects and intersecting surfaces between three-dimensional components, for supporting the recognition of constraints in assembly and disassembly operations in virtual prototyping environments. The implementation of the proposed collision detection algorithm performs well against moderately complex industrial case studies. Current experimental results show that this implementation is effective in determining intersecting surfaces at interactive rates with moderately complex real case studies.info:eu-repo/semantics/publishedVersio

HybridOctree_Hex: Hybrid Octree-Based Adaptive All-Hexahedral Mesh Generation with Jacobian Control

We present a new software package, "HybridOctree_Hex," for adaptive all-hexahedral mesh generation based on hybrid octree and quality improvement with Jacobian control. The proposed HybridOctree_Hex begins by detecting curvatures and narrow regions of the input boundary to identify key surface features and initialize an octree structure. Subsequently, a strongly balanced octree is constructed using the balancing and pairing rules. Inspired by our earlier preliminary hybrid octree-based work, templates are designed to guarantee an all-hexahedral dual mesh generation directly from the strongly balanced octree. With these pre-defined templates, the sophisticated hybrid octree construction step is skipped to achieve an efficient implementation. After that, elements outside and around the boundary are removed to create a core mesh. The boundary points of the core mesh are connected to their corresponding closest points on the surface to fill the buffer zone and build the final mesh. Coupled with smart Laplacian smoothing, HybridOctree_Hex takes advantage of a delicate optimization-based quality improvement method considering geometric fitting, Jacobian and scaled Jacobian, to achieve a minimum scaled Jacobian that is higher than $0.5$. We empirically verify the robustness and efficiency of our method by running the HybridOctree_Hex software on dozens of complex 3D models without any manual intervention or parameter adjustment. We provide the HybridOctree_Hex source code, along with comprehensive results encompassing the input and output files and statistical data in the following repository: https://github.com/CMU-CBML/HybridOctree_Hex

A Method for Clustering and Cooperation in Wireless Multimedia Sensor Networks

Wireless multimedia sensor nodes sense areas that are uncorrelated to the areas covered by radio neighbouring sensors. Thus, node clustering for coordinating multimedia sensing and processing cannot be based on classical sensor clustering algorithms. This paper presents a clustering mechanism for Wireless Multimedia Sensor Networks (WMSNs) based on overlapped Field of View (FoV) areas. Overlapping FoVs in dense networks cause the wasting of power due to redundant area sensing. The main aim of the proposed clustering method is energy conservation and network lifetime prolongation. This objective is achieved through coordination of nodes belonging to the same cluster to perform assigned tasks in a cooperative manner avoiding redundant sensing or processing. A paradigm in this concept, a cooperative scheduling scheme for object detection, is presented based on the proposed clustering method

Unified Spatial Intersection Algorithms Based on Conformal Geometric Algebra

Conformal Geometric Algebra has been introduced into geographic information science as a mathematical theory because of its advantages in terms of uniform multidimensional representation and computation. The traditional intersection computation between two geometric objects of different types is not unified. In this study, we propose algorithms based on Conformal Geometric Algebra to determine the spatial relationships between geographic objects in a unified manner. The unified representation and intersection computation can be realized for geometric objects of different dimensions. Different basic judgment rules are provided for different simple geometries. The algorithms are designed and implemented using MapReduce to improve the efficiency of the algorithms. From the results of several experiments we provide, the correctness and effectiveness of the algorithms can be verified

Fast and Robust Triangle-Triangle Overlap Test Using Orientation Predicates

International audienceThis paper presents an algorithm for determining whether two triangles in three dimensions intersect. The general scheme is identical to the one proposed by Möller (1997). The main difference is that our algorithm relies exclusively on the sign of 4 × 4 determinants and does not need any intermediate explicit construc- tions which are the source of numerical errors. Besides the fact that the resulting code is more reliable than existing methods, it is also more efficient. The source code is available online

Collision Detection and Merging of Deformable B-Spline Surfaces in Virtual Reality Environment

This thesis presents a computational framework for representing, manipulating and merging rigid and deformable freeform objects in virtual reality (VR) environment. The core algorithms for collision detection, merging, and physics-based modeling used within this framework assume that all 3D deformable objects are B-spline surfaces. The interactive design tool can be represented as a B-spline surface, an implicit surface or a point, to allow the user a variety of rigid or deformable tools. The collision detection system utilizes the fact that the blending matrices used to discretize the B-spline surface are independent of the position of the control points and, therefore, can be pre-calculated. Complex B-spline surfaces can be generated by merging various B-spline surface patches using the B-spline surface patches merging algorithm presented in this thesis. Finally, the physics-based modeling system uses the mass-spring representation to determine the deformation and the reaction force values provided to the user. This helps to simulate realistic material behaviour of the model and assist the user in validating the design before performing extensive product detailing or finite element analysis using commercially available CAD software. The novelty of the proposed method stems from the pre-calculated blending matrices used to generate the points for graphical rendering, collision detection, merging of B-spline patches, and nodes for the mass spring system. This approach reduces computational time by avoiding the need to solve complex equations for blending functions of B-splines and perform the inversion of large matrices. This alternative approach to the mechanical concept design will also help to do away with the need to build prototypes for conceptualization and preliminary validation of the idea thereby reducing the time and cost of concept design phase and the wastage of resources

Rock Mass Fracture Detection and Modelling Using GPR for Evaluation and Production Optimization of Ornamental Stone Deposits

The thesis presents new solutions for the fractures problem in ornamental stone quarries which entails economic and material loses. The thesis aimed at developing methodologies and providing solutions for evaluation and production optimization of ornamental stone deposits. Ground Penetrating Radar (GPR) was selected, among several methods, as a fracture detection tool for this research. A combination of the use of a low frequency GPR antenna and laboratory rock tests for evaluation of an ornamental stone deposit showed encouraging results. Based on GPR survey, particularly high frequency antennas, a 3D deterministic fracture modeling approach was developed and implemented in several case studies of block and bench scales. A fracture index was proposed for deposit evaluation based on fracture detections from GPR survey. Additionally, an in-situ GPR test allowed formulating a propagation velocity model for 3D mapping of the dielectric constant of the medium, within macro and micro scale of the rock mass of a bench in a sandstone quarry. This finding is significant for future improvement of the deterministic accuracy level of the developed fracture modeling approach and, generally, for the GPR applications in rock mass. Regarding quarrying optimization, two 3D algorithms, based on fracture modeling or mapping, were developed for production and/or revenue optimization of cutting slabs from blocks and cutting blocks from benches. The algorithms were coded in two software packages named SlabCutOpt and BlockCutOpt. SlabCutOpt was applied to a case study of a limestone block through testing 37 different commercial-sizes of slabs, investigating the optimization results in terms of recovery ratio (a geo-environmental direction) and revenue (an economic direction). BlockCutOpt was applied to two case studies (quarries) with different site characteristics. The results showed that optimum cutting direction of blocks can vertically and horizontally vary, giving geometric information about the cutting grid of blocks that optimizes the production

Ein Modell zur Entwicklung neuartiger chirurgischer Eingriffe am Beispiel der Minimal Traumatischen Chirurgie

In dieser Arbeit wurde eine neuartige Methode zur interindividuellen Untersuchung anatomischer Gegebenheiten entwickelt und an der lateralen Schädelbasis zur Bestimmung der Durchführbarkeit Minimal Traumatischer Eingriffe angewendet. Das Konzept der Minimal Traumatischen Chirurgie wurde erstmals umfangreich aus sowohl medizinischer als auch technischer Sicht beschrieben. Es wurden neue Erkenntnisse gewonnen, die für eine Umsetzung der Minimal Traumatischen Chirurgie von wichtig sind

Displays for Exploration and Comparison of Nested or Intersecting Surfaces

The surfaces of real-world objects almost never intersect, so the human visual system is ill prepared to deal with this rare case. However, the comparison of two similar models or approximations of the same surface can require simultaneous estimation of individual global shape, estimation of point or feature correspondences, and local comparisons of shape and distance between the two surfaces. A key supposition of this work is that these relationships between intersecting surfaces, especially the local relationships, are best understood when the surfaces are displayed such that they do intersect. For instance, the relationships between radiation iso-dose levels and healthy and tumorous tissue is best studied in context with all intersections clearly shown. This dissertation presents new visualization techniques for general layered surfaces, and intersecting surfaces in particular, designed for scientists with problems that require such display. The techniques are enabled by a union/intersection refactoring of intersecting surfaces that converts them into nested surfaces, which are more easily treated for visualization. The techniques are aimed at exploratory visualization, where accurate performance of a variety of tasks is desirable, not just the best technique for one particular task. User studies, utilizing tasks selected based on interviews with scientists, are used to evaluate the effectiveness of the new techniques, and to compare them to some existing, common techniques. The studies show that participants performed the user study tasks more accurately with the new techniques than with the existing techniques