自由变形算法研究及其在头像生成系统中的应用

【作者】 郭际香；

【导师】 章毅；

【作者基本信息】 电子科技大学 ， 计算机软件与理论， 2006， 硕士

【摘要】 随着计算机全面进入3D时代,计算能力的飞速提高和网络应用的蓬勃发展,三维人脸建模和动画已成为计算机图形学领域的研究热点。今天,在娱乐产业、人机交互、多媒体、通讯等领域中三维建模和动画获得了越来越广泛的应用。真实感的三维头像可以应用于诸如电影特技、虚拟电话会议、互联网增值业务和移动互联网增值业务以及软件操作界面等相关领域。在几何造型和计算动画领域中,变形技术已经成为一种越来越重要的工具。通过变形技术可以模拟传统造型和计算机动画技术难以实现的变形效果,如柔性物体的变形、动物的爬行、人脸部运动、表情动画等,因此引起了人们的广泛兴趣和重视。本文研究自由变形算法及其在三维人脸建模和动画中的应用。众所周知,二维空间Dirichlet自由变形算法是一种应用非常广泛的变形算法。和其它算法相比该算法允许用户根据需要设置控制点,抛弃了对控制框架的拓扑结构的限制,使用更为一般的Sibson局部坐标系(Sibson local coordinate system ),因而该算法更具灵活和通用性。关于Dirichlet自由变形算法的研究,目前主要集中在二维情形,本文将二维空间的Dirichlet自由变形算法推广到三维空间中,给出了三维空间中的Dirichlet自由变形算法的具体实现。这种推广远不是一种简单的平行推广!Dirichlet自由变形算法思想的核心在于求控制点的Sibson坐标,也即控制点对物体点的影响值。在二维空间中Sibson局部坐标值是Voronoi单元的面积之比,Voronoi单元是由三角划分得到的三角形的中垂线相交构成,计算简单直观。但推广到三维空间中,Sibson局部坐标值变为Voronoi单元的体积之比,而且Voronoi单元由三角划分得到的四面体棱的中垂面生成,Voronoi单元由面变成体,直观性差,计算也变得相当复杂。因而,从二维Dirichlet自由变形算法到三维Dirichlet自由变形算法的推广具有较强的挑战性。本文将文中提出的三维空间的Dirichlet自由变形算法进一步应用到三维人脸建模和动画中,在此基础上开发了CILAB虚拟头像生成系统。该系统采用Visual C++开发,利用开发式图形库接口OpenGL来处理头像的光照、纹理贴图等,使生成的头像具有较强的真实感。可以方便地应用到各种领域,或提供给用户进行二次开发。更多还原

【Abstract】 With the advent of 3D epoch in computer science, the rapid advance of calculating ability and the flourishing development of networks application, 3D face modeling and animation have become one of the hottest topics in computer graphics research field. Nowadays, 3D modeling and computer animation have got widely applications, such as entertainment industry, man-machine interaction, multimedia, communication etc. The third dimension head portrait has been applied to correlative areas, for examples, movie special effects, virtual conference call, internet increment business, mobile internet increment business and software operation interface etc.In the fields of geometric modeling and computer animation, the deformation technology is an important tool. The deformation technology can simulate many deformations such as the deformation of flexible objects, which is unable to achieve by traditional modeling and computer animation method, so it attracts people’s extensive interest and recognition.This thesis studies the Free Form deformation algorithm and its application in three dimensional face modeling and animation. It is well known that 2D Dirichlet free form deformation algorithm is an extensively used algorithm. This algorithm allows the users design the control frame freely. Compared with other algorithms, it abandons the limitation of topological structure among the control points and uses Sibson local coordinate system, so it is more flexible and universal. So far, the research works on Dirichlet method are mainly centralized in two-dimensional space. This thesis extends this algorithm from two-dimensional space to three-dimensional (3D) space. The realization of the method in 3D space is given in details. This extension is not a simple work at all. The core of Dirichlet free form deformation is in the calculating of the Sibson local coordinate value of the control point, i.e. the influence on the object point by Sibson neighbors. In two-dimensional space, the Sibson coordinate value is the ratio between the areas of Voronoi cells, and the Voronoi cell is made up of the perpendicular bisector of triangles. But in 3D space, the Sibson coordinate value is the ratio between the volumes of Voronoi cells, and the Voronoi cell is made up of the perpendicular face更多还原