【作者】 王明宇；

【导师】 王琰；

【作者基本信息】 沈阳理工大学 ， 计算机软件与理论， 2011， 硕士

【摘要】 虚拟现实技术是计算机图形学和计算机视觉领域研究的一个重要课题,在文物保护、电影特效、广告制作、电子商务等领域有着广泛的应用。对于真实场景的三维重建,通常采用基于三维几何模型为其表面添加纹理的方法来增强真实感,这个过程一般需要两步,构建三维物体的几何模型和为几何模型添加纹理。目前,采用三维扫描采集数据的方法已经可以对真实对象的形状进行三维重建,重建对象纹理就成为了三维重建的研究重点。基于实拍照片的纹理映射主要是指利用数码照相机拍摄获得真实对象的表面纹理,然后利用透视投影矩阵建立三维模型和纹理图像之间的映射关系,将真实纹理映射到三维模型表面,使模型具有真实感。本文针对实拍照片纹理映射中的关键技术进行了研究,主要包括以下内容：(1)分析了纹理映射技术在国内外的发展概况,介绍了与纹理映射技术相关的计算机图形学、计算机视觉、数码相机参数标定理论、图像配准方法等知识；(2)提出了一种利用四组对应点求解相机外部参数的几何标定方法,利用人机交互的方法选取了4组对应点,分别求取了旋转矩阵和平移矩阵,得到了相机的全部外部参数,然后根据相机的内外参数信息求解了透视投影矩阵,建立了三维模型和数码照片之间的映射关系,实现了3D-2DD特征点的配准；(3)基于3D-2D特征点的配准方法关键是确定三维模型和二维图片的3D-2D匹配点,采用了人机交互的方式选取对应特征点对的方法,并提出了一种基于透视投影的快速三维拾取方法,可以较为精确的拾取到模型的三维空间坐标；(4)针对纹理图像存在视角变化的特点,在研究SIFT特征配准算法基础上,采用了马氏距离对SIFT算法误匹配点进行剔除,提高了图像配准的准确率。更多还原

【Abstract】 Virtual reality is an important subject in the field of computer graphics and computer vision, and it has a wide range of applications in cultural relics preservation, special effects on movies, advertising, e-commerce and other fields. Usually,to the 3D reconstruction of real scenes, it will enhance realism through the method that adding texture for the 3D surface model. The process usually takes two steps constructing three-dimensional geometrical model and adding texture for the geometric model. With the developing of photoelectric range finder technology, it has become reality that reconstructing the shape of an object by the 3D scanner. Using digital photos rebuilding objects texture is the key points of the texture mapping research.The texture mapping based on digital photos is that using digital cameras gain actual object surface texture image, and then establish the mapping relationship between 3D model and texture image through perspective projection matrix, mapping the true texture to the surface of 3D model to enhance realism. This paper has a research on the key technologies of the texture mapping based on digital photos, including the following:(1) Introduced the development situation of texture mapping technology at home and abroad, Recountted the theory knowledge related on texture mapping technology, including computer graphics, computer vision, camera calibration theory, image registration method and some other relevant knowledge:(2) In order to solve the calibration of camera extrinsic parameters problem in texture mapping,this paper presents a geometric calibration method based on four point pairs.The first one selects three points in the world coordinate system and calculate their coordinates in the camera coordinate system(world points, light heart, and image point are collinear). Transforms the coordinates to a reference coordinate system and the euclidean distance is invariant. According to the homothetic triangle theory, calculates the rotation matrix and translation vectoer respectively. Finally, gets the complete extrinsic parameters..Applied in the texture mapping, this method can establish a mapping between 3D model and digital photo:(3) The key points of the registration method based on 3D-2D feature points is finding the matching points between 3D model and 2D image. This paper adopts man-machine interactive way of selecting corresponding feature point, and puts forward a fast 3D pick-up method based on the perspective projection. It can pick up the three-dimensional space coordinates;(4) Aiming at the perspective change of the texture images, after research the SIFT features registration algorithm, using Mahalanobis distance eliminate the mismatch points of the SIFT algorithm to improve the accuracy of image registration.更多还原