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1.
增量几何压缩   总被引:9,自引:1,他引:8       下载免费PDF全文
刘新国  鲍虎军  彭群生 《软件学报》2000,11(9):1167-1175
提出了一个几何压缩算法,用以节省三角网格模型存储和传输时间.它首先递归地以区域扩张方式将模型分解为一系列的层结构,利用层间的连贯性以及对层结构的有效编码,实现了高效的拓扑压缩.同时,还设计了一个有效的非线性预测器来实现几何位置的压缩.与以前的算法相比,它具有线性复杂度、压缩比高、执行速度快的特点.实验结果表明,存储一个三角形的拓扑信息平均只需1.42比特.  相似文献
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协同产品开发中的产品模型轻量化技术   总被引:6,自引:1,他引:5  
针对网络环境下协同产品开发中复杂产品模型数据交换、远程传输困难等瓶颈问题。提出一种复杂产品模型数据轻量化算法.该算法基于非几何信息过滤,曲线、曲面简化,通用压缩算法数据压缩等步骤对初始产品模型进行简化.文中算法已应用于协同交互系统InteView2.0中.在相同逼近精度下,轻量化后的模型比原系统输出的VRML格式文件具有更高的压缩比.  相似文献
4.
Internet环境三维流式传输算法研究   总被引:4,自引:0,他引:4  
nternet/Intranet环境的网络带宽和传输速率成为实现协同CAD的瓶颈,针对协同CAD的实时数据传输问题,本文提出了三维流式传输技术,这种新的实时数据传输方法是与视点相关的,将三维几何数据分段、连续地进行传输,可以有效地缩短启动延时,本文具体地研究了相关的实现算法,并通过实验结果证明三维流式传输可以明显地缩短启动延时,能够较好地满足协同CAD的应用需要。  相似文献
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Compressing Triangulated Irregular Networks   总被引:1,自引:0,他引:1  
We address the problem of designing compact data structures for encoding a Triangulated Irregular Network (TIN). In particular, we study the problem of compressing connectivity, i.e., the information describing the topological structure of the TIN, and we propose two new compression methods which have different purposes. The goal of the first method is to minimize the number of bits needed to encode connectivity information: it encodes each vertex once, and at most two bits of connectivity information for each edge of a TIN; algorithms for coding and decoding the corresponding bitstream are simple and efficient. A practical evaluation shows compression rates of about 4.2 bits per vertex, which are comparable with those achieved by more complex methods. The second method compresses a TIN at progressive levels of detail and it is based on a strategy which iteratively removes a vertex from a TIN according to an error-based criterion. Encoding and decoding algorithms are presented and compared with other approaches to progressive compression. Our method can encode more general types of triangulations, such as those constrained by topographic features, at the cost of a slightly longer bitstream.  相似文献
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Z.M. Qiu  Y.S. Wong  Y.P. Chen  W.D. Li 《Computer》2004,36(9):809-819
Visualization of CAD models in distributed design environment is an essential feature to support collaborative design. To efficiently transmit and render CAD models geometric simplification can be applied to CAD models. However, it is difficult to use available general geometric simplification algorithms because these algorithms are not designed to handle mechanical CAD parts. Applying general simplification on a CAD model would result in distortion of design features and make them unrecognizable to viewers. In this paper, a novel approach is proposed to exploit trimming information in CAD models to simplify their geometry. Visibility culling is integrated into this approach to facilitate selective refinements. The work introduced here aims to support visualization of multiple CAD models in a distributed CAD environment. Implementation details are included and case studies are demonstrated.  相似文献
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The majority of methods for the automatic surface reconstruction of an environment from an image sequence have two steps: Structure-from-Motion and dense stereo. From the computational standpoint, it would be interesting to avoid dense stereo and to generate a surface directly from the sparse cloud of 3D points and their visibility information provided by Structure-from-Motion. The previous attempts to solve this problem are currently very limited: the surface is non-manifold or has zero genus, the experiments are done on small scenes or objects using a few dozens of images. Our solution does not have these limitations. Furthermore, we experiment with hand-held or helmet-held catadioptric cameras moving in a city and generate 3D models such that the camera trajectory can be longer than one kilometer.  相似文献
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Limitations of current 3D acquisition technology often lead to polygonal meshes exhibiting a number of geometrical and topological defects which prevent them from widespread use. In this paper we present a new method for model repair which takes as input an arbitrary polygonal mesh and outputs a valid 2-manifold triangle mesh. Unlike previous work, our method allows users to quickly identify areas with potential topological errors and to choose how to fix them in a user-friendly manner. Key steps of our algorithm include the conversion of the input model into a set of voxels, the use of morphological operators to allow the user to modify the topology of the discrete model, and the conversion of the corrected voxel set back into a 2-manifold triangle mesh. Our experiments demonstrate that the proposed algorithm is suitable for repairing meshes of a large class of shapes.  相似文献
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In the automotive, aerospace and naval industries, digital mock-up tools are always used for assembly examination, layout examination and interference checking. Generally, a digital mock-up is assembled from giga-scale CAD models. Because of limitations of computer hardware resources, a digital mock-up represented by traditional planar facets is too large to load into a computer’s memory for rendering. This article proposes a new geometric compression representation to represent given CAD models with curved triangular patches. Based on the compression representation, our digital mock-up visualization system can import several giga-scale CAD models into a computer’s memory simultaneously. A high performance rendering strategy to display the curved triangular patches is also presented. In the rendering strategy, a dynamic subdivision algorithm is introduced which is different from conventional LOD techniques in order to reduce memory consumption. In addition, an algorithm to convert CAD models to the curved triangular patches is introduced.  相似文献
10.
This paper applies singularity theory of mappings of surfaces to 3-space and the generic transitions occurring in their deformations to develop algorithms for continuously and robustly tracking the intersection curves of two deforming parametric spline surfaces, when the deformation is represented as a family of generalized offset surfaces. The set of intersection curves of two deforming surfaces over all time is formulated as an implicit 2-manifold I in an augmented (by time domain) parametric space R5. Hyperplanes corresponding to some fixed time instants may touchI at some isolated transition points, which delineate transition events, i.e. the topological changes to the intersection curves. These transition points are the 0-dimensional solution to a rational system of five constraints in five variables, and can be computed efficiently and robustly with a rational constraint solver using subdivision and hyper-tangent bounding cones. The actual transition events are computed by contouring the local osculating paraboloids. Away from any transition points, the intersection curves do not change topology and evolve according to a simple evolution vector field that is constructed in the Euclidean space in which the surfaces are embedded.  相似文献
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