【作者】 胡斌；

【导师】 费耀平；

【作者基本信息】 中南大学 ， 计算机应用技术， 2008， 硕士

【摘要】 随着三维模型扫描设备和交互式建模工具的快速发展和广泛使用,近年来三维模型的数量快速增长。三维模型在众多领域发挥了重要的作用,很多大型三维模型数据库相继出现,如何从数据库中获取所需的三维模型成为一个迫切需要解决的问题。本文以基于球面调和变换的特征提取算法为研究对象,对三维模型检索的关键技术进行了详细的研究,主要工作包括以下几个方面:从三维模型空间分布的基本特征出发,系统地定义了4种球面函数,从不同角度描述了三维模型。对这4种球面函数进行球面调和变换,在此基础上构建了4种基于单个球面函数的特征描述符。实验结果表明,这4种特征描述符具有良好的检索性能和对模型噪声、缩放、旋转和简化的鲁棒性。针对单个球面函数特征表达能力有限的问题,提出了基于多球面函数的扩展特征描述符,综合使用多个球面函数来构建特征向量。针对单个球面函数没有考虑三维模型在球面方向上离质心不同距离处的特征,提出了基于同心球壳划分的扩展特征描述符,将单个球面函数分解为描述三维模型在各个球壳中空间分布特征的球面函数序列,利用这个球面函数序列来构建特征描述符。实验结果表明,综合考虑多个球面函数能更全面地描述三维模型的空间分布特征,将球面函数分解为一个球面函数序列能更有效地描述三维模型在不同球壳内的空间分布特征,提高了特征描述符的检索性能。结合以上两种扩展方法,提出了基于多球面函数序列的特征描述符,综合考虑多个球面函数序列来构建特征向量。实验结果表明,基于多球面函数序列的特征描述符综合了两种扩展方法的长处,具有最好检索性能,其中基于全部4种球面函数序列的特征描述符的检索性能要优于已有的基于球面调和变换的特征描述符。更多还原

【Abstract】 With the rapid development and extensive use of new scanners and interactive modeling tools, the number of 3D models increases quickly recent years. 3D model plays a more and more important part in many fields and many large 3D model repositories come forth. The need for retrieval of models from large repositories of 3D shapes has gained prominence in the graphic and vision communities. This paper focusd on feature extraction algorithm based on spherical harmonics, analyzed and investigated the key technologies in 3D model retrieval.The most important part of feature extraction algorithm based on spherical harmonics was to define spherical function which describes centain feature of 3D models. In this paper, four spherical functions based on 3D model geometry feature was defined, each spherical function describe 3D model from a certain point of view. Then, spherical harmonic transform was used on these functions and the energy of the coefficients of spherical harmonics was used to form four 3D feature descriptors. The experimental results indicate that those four feature descriptors have pretty good retrieval performance and robustness to rotate, simplification, scale and noise.Because the discrimination power of feature descriptors based on single spherical function was limited, two types of extended feature descriptors was proposed: feature descriptors based on multiple spherical function and feature descriptors based on concentric sphere partition. These two types of extended feature descriotor improved feature descriptors based on single spherical function from two aspects and those two methods could be integrated to construct feature descriptors based on multiple spherical function sequence. This paper presented the basic frame of feature extraction algoritm of those types of feature descriptor. The experimental results indicate that those two methods could improve retrieval performance of feature descriptor, and the feature descriptor based on multiple spherical function sequence had the best retrieval performance.更多还原