共查询到18条相似文献,搜索用时 46 毫秒
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提出了一种基于四边形网格的可调细分曲面造型方法。该方法不仅适合闭域拓扑结构,且对初始网格是开域的也能进行处理。细分算法中引入了可调参数,增加了曲面造型的灵活性。在给定初始数据的条件下,曲面造型时可以通过调节参数来控制极限曲面的形状。该方法可以生成C1连续的细分曲面。试验表明该方法生成光滑曲面是有效的。 相似文献
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论文主要研究混合网格的曲面细分问题,提出了一种带有可调参数的细分算法。该算法适用于多边形网格、三角形网格,以及两者的混合网格情形,且对开的和闭的拓扑结构都能进行处理。由于在算法中引入了可调参数,这样既可产生光滑曲面,也可产生具有尖锐特征的曲面,且通过调整参数还可产生标准的Catmull-Clark细分和Loop细分。另外,实现该算法不需要复杂的数据结构。 相似文献
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吴元翠 《数字社区&智能家居》2013,(13):3142-3145
首先研究了传统的Loop细分曲面算法,通过分析发现随着细分次数的增多细分算法中三角形网格片数增长过快。针对这一问题提出一种自适应细分曲面算法。算法根据相邻两个三角形面上的法向量的夹角,判断细分网格中较为光滑和非光滑的区域。实验结果表明,算法提高了数据处理速度,并且模型简单易实现。 相似文献
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本文研究了曲面造型中的细分曲面造型方法,分析了细分曲面造型的优点。基于多边形网格的细分方法分析了基于三角形网格1-4分裂的Loop细分模式的优点,并实现了基于Loop细分模式的曲面造型。利用Loop细分模式进行两次细分,得到不同网格密度的数据,最后本文给出了细分前后的点数、边数以及面数,并显示了细分前后的点的效果图。 相似文献
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提出了一种新的自适应细分算法,在顶点的1-邻域内,用与顶点相连较长三条边的端点构成的平面去替代其平均平面,将顶点到其平均平面的距离作为判断顶点重要度的标准,对三角网格进行自适应细分。由于原始三角面片的高密度和形状相似性,以点面距离为细分尺度所产生的误差,可被限制在一个体元之内,与反复修正顶点法矢算法相比,该算法大大减少了计算量。实验结果表明,所提方法在三角网格细分过程中,简化了数据模型,提高了处理速度。 相似文献
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在初始控制网格确定的情况下,生成的曲面形状惟一确定,最终的物体造型也随之确定,不具有可调性.通过在曲面细分过程中引入一个参数,给出一种新的细分曲面构造的算法,使得所得的细分曲面的表达度可控.调节一个参数值,可以得到一系列的细分曲面.最后给出了曲面设计的实例,表明这种算法简单、有效. 相似文献
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We introduce a non-uniform subdivision algorithm that partitions the neighborhood of an extraordinary point in the ratio σ:1−σ, where σ(0,1). We call σ the speed of the non-uniform subdivision and verify C1 continuity of the limit surface. For σ=1/2, the Catmull–Clark limit surface is recovered. Other speeds are useful to vary the relative width of the polynomial spline rings generated from extraordinary nodes. 相似文献
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Mesh compression is an important task in geometry processing. It exploits geometric coherence of the data to reduce the amount of space needed to store a surface mesh. Most techniques perform compression employing a uniform data quantization over the whole surface. Research in shape perception, however, suggests that there are parts of the mesh that are visually more relevant than others. We present a novel technique that performs an adaptive compression of a static mesh, using the largest part of the bit budget on the relevant vertices while saving space on encoding the less significant ones. Our technique can be easily adapted to work with any perception-based error metric. The experiments show that our adaptive approach is at least comparable with other state-of-the-art techniques, while in some cases it provides a significant reduction of the bitrate of up to 15%. Additionally, our approach provides much faster decoding times than comparable perception-motivated compression algorithms. 相似文献
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球面离散格网模型单元的面积、形状是否相似关系到模型的精度,因此定量分析单元的几何变形、分布规律等是格网模型建模的重要组成部分。文章通过对基于正八面体和正二十面体球面剖分获得的球面三角单元进行分析,分析结果表明随着剖分层次的增加单元面积和形状变化趋于稳定,基于正二十面体的球面剖分与基于正八面体相比有更好的相似性;单元的变形程度与其到正多面体顶点的距离成负相关,而周长和面积变化成正相关;单元各属性比值所占的百分比与剖分层次无关,其较大峰值都分布在正多面体的顶点附近。 相似文献
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REN Shui-li ZHANG Kai-yuan YE Zheng-lin 《通讯和计算机》2007,4(5):57-61
Based on triangle and quadrilateral meshes, this paper presents an adjustable subdivision surface scheme. The scheme can produce subdivision surface of Cl continuity of limit surface Since an adjustable parameter is introduced to the scheme, the surface modeling is flexible. Depended on given initial data, the limited surface shape can be adjusted and controlled through selecting appropriate parameters. The method is effective in generating smooth surfaces. 相似文献
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With the exponential growth in size of geometric data, it is becoming increasingly important to make effective use of multilevel caches, limited disk storage, and bandwidth. As a result, recent work in the visualization community has focused either on designing sequential access compression schemes or on producing cache-coherent layouts of (uncompressed) meshes for random access. Unfortunately combining these two strategies is challenging as they fundamentally assume conflicting modes of data access. In this paper, we propose a novel order-preserving compression method that supports transparent random access to compressed triangle meshes. Our decompression method selectively fetches from disk, decodes, and caches in memory requested parts of a mesh. We also provide a general mesh access API for seamless mesh traversal and incidence queries. While the method imposes no particular mesh layout, it is especially suitable for cache-oblivious layouts, which minimize the number of decompression I/O requests and provide high cache utilization during access to decompressed, in-memory portions of the mesh. Moreover, the transparency of our scheme enables improved performance without the need for application code changes. We achieve compression rates on the order of 20:1 and significantly improved I/O performance due to reduced data transfer. To demonstrate the benefits of our method, we implement two common applications as benchmarks. By using cache-oblivious layouts for the input models, we observe 2?6 times overall speedup compared to using uncompressed meshes. 相似文献
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《Computer Aided Geometric Design》2007,24(6):361-370
A well-documented problem of Catmull and Clark subdivision surfaces is that, in the neighborhood of extraordinary points, the curvature is unbounded and fluctuates. In fact, since one of the eigenvalues that determines elliptic shape is too small, the limit surface can have a saddle point when the designer's input mesh suggests a convex shape. Here, we replace, near the extraordinary point, Catmull–Clark subdivision by another set of rules based on refining each bi-cubic B-spline into nine. This provides many localized degrees of freedom for special rules that need not reach out to neighbor vertices in order to tune the behavior. In this paper, we provide a strategy for setting such degrees of freedom and exhibit tuned ternary quad subdivision that yields surfaces with bounded curvature, nonnegative weights and full contribution of elliptic and hyperbolic shape components. 相似文献
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Constructing hierarchies for triangle meshes 总被引:5,自引:0,他引:5
Gieng T.S. Hamann B. Joy K.I. Schussman G.L. Trotts I.J. 《IEEE transactions on visualization and computer graphics》1998,4(2):145-161
We present a method to produce a hierarchy of triangle meshes that can be used to blend different levels of detail in a smooth fashion. The algorithm produces a sequence of meshes M0, M1, M 2..., Mn, where each mesh Mi can be transformed to mesh Mi+1 through a set of triangle-collapse operations. For each triangle, a function is generated that approximates the underlying surface in the area of the triangle, and this function serves as a basis for assigning a weight to the triangle in the ordering operation and for supplying the points to which the triangles are collapsed. The algorithm produces a limited number of intermediate meshes by selecting, at each step, a number of triangles that can be collapsed simultaneously. This technique allows us to view a triangulated surface model at varying levels of detail while insuring that the simplified mesh approximates the original surface well 相似文献