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Surface Fairing and Surface Compression for 3D Ship Modeling

用于 3D 船舶建模的表面光整和表面压缩

基本信息

批准号：
12450398
负责人：
MASUDA Hiroshi
金额：
$ 9.6万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

The purposes of this research are the development of an automatic surface fairing method for 3D ship-hull design and the development of a surface compression method for exchanging 3D data. The results of them are described as follows :1. Surface FairingSurfaces generated by conventional fairing methods often have unwanted features such as local perturbations and global waves. This research developed a new fairing method that avoids these features. The method consists of the following three steps. (1) Rearranging control points of lines-curves so that the weighted sum of their arc lengths and curvatures are equally distributed. (2) Rearranging control points along lines-curves by applying low-pass filters repeatedly. (3) For eliminating the local perturbations, an energy minimization technique for thin-plates is used by regarding each surface as a thin-plate. Our method was applied to examples of hull-form surfaces, and could effectively remove the both of global waves and local perturbations with limited changes of the shape.2. Surface CompressionSurface compression is effective for storing and distributing 3D CAD data, but existing compression methods failed to maintain the smoothness at surface boundaries. In our method, a NURBS surface is encoded using its boundaries and additional data. At first, an interpolating surface is calculated using the boundary curves of the original surface. Then, the differences between the original surface and the interpolating one are calculated. Difference data are optionally used, and they are represented in two types : distances only, and distances and orientations. One type is selected according to the tolerances of each surface. Finally, the boundary curves and the difference data are compressed using the discrete cosine trans-form (DCT). The results show our method can easily control the trade-off between the compression ratio and accuracy, and achieve a good compression rates. (291 words)

本研究的目的是发展一种适用于三维船体设计的自动曲面光顺方法和一种用于交换三维数据的曲面压缩方法。研究结果如下：1.曲面光顺由传统光顺方法生成的曲面通常具有不需要的特征，例如局部扰动和全局波。本研究开发了一种新的光顺方法，避免这些功能。该方法包括以下三个步骤。(1)重新排列直线曲线的控制点，使其弧长和曲率的加权和均匀分布。(2)通过重复应用低通滤波器来重新排列沿着曲线的控制点。(3)为了消除局部扰动，薄板的能量最小化技术被用来作为一个薄板的每个表面。将该方法应用于船体曲面的实例，在形状变化有限的情况下，能够有效地去除全局波动和局部扰动.表面压缩表面压缩对于存储和分发3D CAD数据是有效的，但是现有的压缩方法不能保持表面边界处的平滑。在我们的方法中，NURBS曲面使用其边界和附加数据进行编码。首先，利用原始曲面的边界曲线计算插值曲面。然后，计算原始曲面和插值曲面之间的差异。可以选择使用差异数据，并且它们以两种类型表示：仅距离，以及距离和方向。根据每个表面的公差选择一种类型。最后，利用离散余弦变换（DCT）对边界曲线和差分数据进行压缩。实验结果表明，该方法可以很好地控制压缩比和精度之间的平衡，并获得较好的压缩率。(291字）