基于对称物体的3维重构技术研究

3维重构理论与技术是计算机视觉领域最重要的热点问题之一,而基于单幅图像的3维重构由于缺乏足够的几何信息而难以达到预期效果,已成为世纪性难题。针对大部分物体具有对称性特征,或可分解为有限个对称物体元的客观事实,提出基于透视逆变换原理,首先建立包含摇角、倾角、摆角等三元的透视变换矩阵T;再由链码表示的物体轮廓提取特征直线,根据平行线束投影角相近性特点求解主灭点信息,进而确定视点位置、物体对称平面;根据对称性特征,利用物体假想对称平面,通过人工交互指定3对已知对称点的图像坐标及其对应点的空间坐标确定透视变换矩阵T,继而反求物体表面其他特征点的空间位置,最后利用OpenGL软件包实现物体3维模型的重建。     

基于多感知因素的产品三维重构关键技术研究

从一幅简单的图形出发,利用图像中隐藏的透视信息进行三维重构,计算产品特征点的坐标及其相对位置.进行了透视元素、基本体素到组合体素的反求研究,并且给出了其相应的原理和算法.对于几何残缺信息的视觉补偿与推理等关键算法进行了研究,并利用非几何信息的处理与特征建模,搭建基于产品多感知因素的三维重构系统框架,实现了设计重用辅助产品创新设计.     

基于多感知因素的产品三维重构关键技术研究*

从一幅简单的图形出发,利用图像中隐藏的透视信息进行三维重构,计算产品特征点的坐标及其相对位置。进行了透视元素、基本体素到组合体素的反求研究,并且给出了其相应的原理和算法。对于几何残缺信息的视觉补偿与推理等关键算法进行了研究,并利用非几何信息的处理与特征建模,搭建基于产品多感知因素的三维重构系统框架,实现了设计重用辅助产品创新设计。     

基于距离变换的图像层间插值技术

由断层图像恢复出目标物体的三维图像应用极广，文中提出了基于距离交换的断层图像插值方法来获得三维重构时的数据场。此方法由于在插值时考虑了目标物体的整体特征，从而使得插值具有连续性。     

信号博弈的三维重建形变识别算法

现有双目立体视觉算法常常需要双目相机位置固定,在现实应用中,这类算法难以重构空间三维几何关系.为此,本文提出了一种不受位置限制的多视角图像三维重建与形变检测算法.该算法首先采用sift算法获取成对图像的特征点,以获取形变前后比对点对图像的特征信息;其次,利用信号博弈方法确定图像拍摄时相机的空间位置与视角,以准确获取图像的空间位置坐标;再次,依据上述信息完成物体的三维点云重建;进而,利用三维数据信息比对实现物体形变识别.最后,本文利用真实物体的实验,验证了三维重建形变识别算法的有效性.     

基于SFS原理的SMT焊点表面三维重构技术研究

基于明暗重构形状原理重构表面组装焊点的表面三维形状过程是:先通过图像采集设备,采集到SMT焊点图像,使用相关的图像处理技术,对SMT焊点图像进行处理;根据一个确定的反射模型建立物体表面形状与图像亮度之间的约束关系和物体表面形状的先验知识建立物体表面形状参数的约束关系,然后对这些约束关系联立求解,可得到物体表面的三维形状.同时针对不可接受SMT焊点图像重构出的三维图像不够理想的缺点进行了改进.在阐述其基本思想和原理的基础上,结合实例介绍了该技术的实现方法与步骤,对其中焊点图像的获取与处理、焊点三维重构技术算法等主要内容与关键技术进行了研究和探讨,并对结果进行了分析验证.     

一种基于二维图像的三维仿真方法研究

针对二维的图像数据,综合运用计算机视觉、计算机图像处理和计算机辅助几何设计理论与技术,提出了一种实用的三维仿真方法.采用阴影恢复形状的方法获取三维形貌信息,利用图像分割技术提取物体的二维轮廓信息,通过三维形貌信息与二维轮廓信息的融合技术建立物体的数字化模型,通过B样条的万法实现数字化模型的重构.实例表明,方法可行有效,能够有效地去除图像的背景信息,改善重构模型的分辨力,为基于二维图像的三维仿真技术的广泛应用提供了条件.     

基于轮廓和多相关局部顶点优化的三维重构法

如何快速准确的获取真实物体的三维模型受到了人们的普遍关注,针对这个问题,给出了一种能够利用一系列已标定图像中的侧影轮廓线信息重构模型的建模方法.方法中摄像机以物体为中心做圆周运动,间隔固定的角度进行拍照.对获取的图像进行处理,提取其侧影轮廓线.使用Marching Cubes算法重构物体的表面,利用物体在多幅图像中的纹理一致性原理,进行多相关局部顶点优化,并应用到了模型顶点的优化过程之中.最终可以得到品质较好的三维网格表示的物体的三维模型.     

利用Helmholtz互易原理由两对图像重建物体三维表面

针对利用Helmhohz互易原理由一对图像重构三维表面时存在计算时间长、显示质量不高的问题,提出一种利用上下对、左右对图像重建三维物体表面的高效算法.利用其中一对图像的匹配结果分割另一对图像的外极线,将整个外极线的匹配问题转化为相应子段的匹配问题,并交错地递归这种处理过程;引入不要求端点匹配的动态规划匹配算法实现子段对应,并分段重构物体=三维表面的点.实验结果表明,与单对图像重构算法相比,该算法能够大幅度地缩小动态规划算法的搜索范围,使得重构速度提高了一个数量级;通过上下、左右方向扫描线恢复三维表面点并大约增加0.5倍的重构点数量,使得表面显示质量得到明显提高.     

基于多粒度匹配的高超速飞行体三维重构方法

针对高超速飞行体在飞行过程中能获取到的图像信息较少,无法完全复现其轮廓信息,提出一种基于多粒度匹配的三维重构优化方法。首先通过两台高分辨率CCD相机正交的阴影照相站系统采集高超速飞行体多幅图像信息,利用图像分割技术提取物体的二维轮廓;然后采用改进的SFS算法求解出物体表面各点的相对高度和表面法向量,恢复其三维形貌;最后使用图像拼接优化技术实现高超速飞行体表面的三维重构。并经过实体模型的三维重构验证所提方法的可行性及有效性。     

基于数据学习逆模糊模型的自适应逆模糊控制

针对在逆模糊模型控制中出现的在线滚动数据窗口计算量大和控制模型精度低等问题,提出了基于数据逆模糊学习算法,并将该算法运用到建立逆模糊模型中。首先利用建模数据在时间与空间相邻的特点,从系统积累的数据中找出与当前模态相匹配的输入数据,在保证控制模型精度的同时大大减少了计算量,然后采用自适应算法在线调节系统模型参数,实现非线性系统的实时跟踪控制。该方法提高了系统控制精度与计算效率。仿真结果证明了该方法的有效性。     

Inverse NP Problems

The inverse problem relative to a verifier V of proofs of membership for a NP language is the problem of deciding, given a set π of proofs, whether or not there exists a string x having exactly π as its set of proofs. In this paper, we study the complexity of inverse problems. We develop a new notion of reduction which allows one to compare the complexity of inverse problems. Using this notion, we classify as coNP-complete the inverse problems for the “natural” verifiers of many NP-complete problems. We also show that the inverse complexity of a verifier for a language L cannot be predicted solely from the complexity of L, but rather, is highly dependent upon the choice of verifier used to accept L. In this context, a verifier with a Σ₂ ^p -complete inverse problem is exhibited, giving a new and natural example of a Σ₂ ^p -complete problem.      

Hyperspectral Inverse Skinning

In example-based inverse linear blend skinning (LBS), a collection of poses (e.g. animation frames) are given, and the goal is finding skinning weights and transformation matrices that closely reproduce the input. These poses may come from physical simulation, direct mesh editing, motion capture or another deformation rig. We provide a re-formulation of inverse skinning as a problem in high-dimensional Euclidean space. The transformation matrices applied to a vertex across all poses can be thought of as a point in high dimensions. We cast the inverse LBS problem as one of finding a tight-fitting simplex around these points (a well-studied problem in hyperspectral imaging). Although we do not observe transformation matrices directly, the 3D position of a vertex across all of its poses defines an affine subspace, or flat. We solve a ‘closest flat’ optimization problem to find points on these flats, and then compute a minimum-volume enclosing simplex whose vertices are the transformation matrices and whose barycentric coordinates are the skinning weights. We are able to create LBS rigs with state-of-the-art reconstruction error and state-of-the-art compression ratios for mesh animation sequences. Our solution does not consider weight sparsity or the rigidity of recovered transformations. We include observations and insights into the closest flat problem. Its ideal solution and optimal LBS reconstruction error remain an open problem.     

逆P-信息嵌入隐藏与它的逆P-推理分离-发现

逆P-集合(inverse packet sets)是由内逆P-集合F(internal inverse packet set F)与外逆P-集合(outer inverse packet set )构成的集合对;或者()是逆P-集合。逆P-集合是把动态特性引入到有限普通集合X内(Cantor set X),改进有限普通集合X得到的。逆P-集合具有与P-集合相反的动态特性。利用逆P-集合给出逆P-信息的概念、逆P-信息嵌入隐藏与嵌入-隐藏定理、逆P-信息的隐藏还原属性特征、逆P-信息嵌入隐藏的逆P-推理分离-发现。利用这些结果,给出逆P-信息嵌入隐藏的逆P-推理分离-发现的应用。     

Inverse Displacement Mapping

Inverse displacement mapping is a variant of displacement mapping which does not actually perturb the geometry of the surface being mapped. It is thus a true texture mapping technique which can be applied during rendering without breaking viewing pipeline discipline. The method works by first projecting probing rays into texture space and solving for a ray-texture intersection there. Shadows can also be determined by mapping a probe from the intersection point towards the light source into texture space and seeing if an intersection results. Our implementation uses as much knowledge about the base surface as possible to speed up the ray-surface intersection calculation. We have limited our treatment to spheres, cones, cylinders and planes, and our rendering method to ray casting, in order to contain the scope of this work up to the present. The inverse displacement mapping technique can, however, be applied more widely, for example as part of a full ray-tracer, and also as part of the rendering pipeline for a wider class of smooth surfaces.     

基于DSP的AVS反量化反变换的实现

描述了AVS中的反量化和反变换算法的DSP实现.采用TI公司的TMS320C5502作为处理芯片,根据芯片的结构、汇编指令、存储器读取的特点,针对视频解码的实时性要求,给出了一种适合该芯片的快速实现方法.通过DSP的仿真验证,对比了几种实现方法,证明了这一方法的可行性和高效性,最后将给出实验结果及分析.     

角色反演算法

给出了面向上下文无关语言的句法分析的一种计算机制:角色反演算法.这种机制通过引入句法范畴的"角色"这一概念以及相应的角色反演操作,用较小的空间代价在Chart算法中实现了较强的"预读"(look ahead)功能.这使其能节约大量的无用边,从而加速分析过程的推进.这种机制可以用于自然语言处理等多种应用领域.     

The Inverse Classification Problem

In this paper, we examine an emerging variation of the classification problem, which is known as the inverse classification problem. In this problem, we determine the features to be used to create a record which will result in a desired class label. Such an approach is useful in applications in which it is an objective to determine a set of actions to be taken in order to guide the data mining application towards a desired solution. This system can be used for a variety of decision support applications whic...     

High Performance Inverse Preconditioning

The derivation of parallel numerical algorithms for solving sparse linear systems on modern computer systems and software platforms has attracted the attention of many researchers over the years. In this paper we present an overview on the design issues of parallel approximate inverse matrix algorithms, based on an anti-diagonal “wave pattern” approach and a “fish-bone” computational procedure, for computing explicitly various families of exact and approximate inverses for solving sparse linear systems. Parallel preconditioned conjugate gradient-type schemes in conjunction with parallel approximate inverses are presented for the efficient solution of sparse linear systems. Applications of the proposed parallel methods by solving characteristic sparse linear systems on symmetric multiprocessor systems and distributed systems are discussed and the parallel performance of the proposed schemes is given, using MPI, OpenMP and Java multithreading.