保持特征的对偶网格构造方法

针对对偶网格萎缩现象,提出一种基于全局能量优化的对偶网格构造方法.该方法从重建原始网格、保持原网格形状和对偶网格质量修正3个角度建立能量优化模型,并通过求解稀疏线性方程组得到对偶网格的顶点位置;得益于该方法的重建能量约束,利用重构约束矩阵与对偶网格顶点位置可以很快地重建原始网格.实验结果表明,文中方法避免了网格萎缩现象,且适用于任何拓扑结构的模型;基于该方法的网格编辑算法可以很好地保持原始网格的几何形状特征.     

混合动力电动汽车能量管理控制策略及仿真

研究电动汽车能量管理优化控制问题,混合动力电动汽车(HEV)能量管理系统,由于动力效率决定于发动机性能控制。针对传统方法燃油利用率低,车辆驾驶控制方式影响了优化。为了提高能源优化效率及优化驾驶控制,提出了一种燃油经济性和驾驶性能全局优化的能量管理控制策略。首先在系统中加入驾驶性能变量,并在代价函数中加入驾驶性能限制,然后把HEV能量管理问题建模为多步决策过程问题,运用动态规划(DP)原理,得到了全局优化的能量管理控制器。将该控制器模型嵌入高级车辆仿真器ADVISOR的并联车辆模型中,与传统规则的控制策略进行仿真对比。仿真结果表明,新的控制策略使燃油经济性提高了约16%,并且使驾驶性能控制在良好的范围内,能有效提高HEV能量管理的效率和实用性,为优化设计提供了依据。     

基于增量SVR模型的改进全局优化算法

SVR(支持向量回归)是一种具有较强稳健性的小样本学习方法,它可有效避免"维数灾难",并被引入到全局优化中。然而现有的基于SVR的全局优化算法存在估值次数多、无法应对高维优化问题等缺点。提出了一种基于增量SVR模型的新的改进全局优化算法DISVR:采用增量SVR方法提高过程响应面的重构效率;采用一种新的增量LHD(Latin Hyper-cube Sampling)方法确保样本集分布均匀;采用DIRECT搜索算法提高全局搜索的稳定性和效率。最后,通过多个测试函数表明,该算法既降低了时间复杂度,也有效减少了源模型的估值次数。     

IHLS颜色空间的灰度化全局非线性三向映射

为了减少彩色图像转化为灰度图像过程中颜色信息的损失,基于人眼感知明度的视觉模型,提出一种全局灰度化方法.首先使用彩色图像的IHLS颜色空间,建立了关于亮度、色度和饱和度3个因子的全局非线性映射模型;然后将该映射模型中全局参数的计算转化为一个能量函数的优化,其中第一个能量项度量了彩色图像和灰度图像梯度的差异,第二个能量项定义了图像中给定一个像素与其随机采样点集之间两两彩色距离与灰度距离的差异;最小化上述2个能量项可以通过3个因子的迭代算法进行求解.大量的实验结果表明,该方法可更好地反映人眼对彩色图像的感知,使得灰度转化结果更加贴近颜色的感知明度.     

斜面参数优化全局立体匹配算法研究

针对现有立体匹配算法在非平行平面区域匹配中出现“阶梯效应”的问题,提出一种斜面参数优化的全局立体匹配算法。该算法用斜面参数替代视差值作为全局匹配算法的优化变量,并结合粒子滤波思想实现斜面参数的（近似）连续取值及能量函数的连续域全局优化,理论上可以同时消除传统匹配算法中视差离散取值及视差一致性约束带来的影响,从根本上消除“阶梯效应”。针对典型非平行平面测试图像对的实验结果表明,该算法在有效消除“阶梯效应”的同时降低了误匹配率。     

采用窄带图切割的多目重构方法

针对目前多目重构研究中物体表面获取和凹陷区域恢复的难题,提出采用窄带图切割的可见外壳和多目立体匹配相融合的方法.在可见外壳的拓扑约束下,通过最小化能量泛函使得重构表面与多目立体匹配得到的稠密点云形状一致;并利用窄带图切割计算能量泛函的全局最优解.实验结果表明,该方法能重构封闭表面和凹陷区域;窄带图切割在获得最优解的同时提高了计算效率,与全图切割相比速度提高了3倍以上.     

一种双种群协同进化算法在湿法炼锌过程中的应用

为了求解针铁矿法沉铁过程的多目标协调优化模型,从提高全局寻优能力和解的精度出发,提出一种基于改进全局搜索量子进化算法和局部搜索差分进化算法的双种群协同进化算法.数值仿真验证了该进化算法具有较好的收敛性和求解精度;典型工况的仿真优化结果表明了该多目标协调优化模型指导实际生产的可行性,以及所提出算法的有效性.     

基于化学反应算法的系统辨识

化学反应优化算法起源于化学反应过程中的能量变化的模拟。提出一种利用化学反应优化算法对系统进行辨识的方法。即通过建立连续系统和离散系统的传递函数结构模型,首先将系统辨识问题转化为数学上求取相关参数的全局最优估计问题,然后利用化学反应优化算法对该问题进行求解。最后给出仿真实例,并且与遗传算法进行了比较,结果表明该方法具有较好的效果,且兼具速度快、精度高等特点。     

一种基于简单笔画交互的迭代图像抠图方法

为了获得精确的和视觉上连续的抠图结果,提出了一种基于简单笔画的图像抠图方法,该方法仅需要用户以少量笔画和拖拽矩形框的方式指定前景和背景像素即可实现。该方法从亮度,纹理和空间位置多特征空间考虑像素的分布,首先建立了鲁棒的颜色分布模型;然后在此基础上,定义采样约束函数,再来获取精确的前景和背景样本;最后基于样本信息和平滑性约束,为所有未知像素构造了一个全局的能量函数,再通过迭代的优化将用户约束传播到整个未知区域。实验结果表明,该方法不仅保持了抠图结果的精确性和视觉上的连续性,并能够有效地处理纹理丰富和具有相似的前景与背景颜色的输入图像。     

MANET环境下一种利用缓冲的多连接算法

对MANET环境下的多连接查询技术进行了研究,提出了一种利用缓冲的多连接算法.该算法从全局和局部两方面对查询进行了优化,全局优化阶段获得一个能量最优的查询计划,该计划确定出各子查询及其结果放置节点;局部优化阶段为每个子查询确定执行计划.实验证明,提出的方法不仅能显著地减少查询执行的能量消耗,而且能很好地适应MANET网络中节点多跳通信和拓扑动态变化的特点.     

A high-quality 3D multiview model-building technique based on CAD

In this paper, we propose a method for building a high-quality 3D model efficiently from a CAD model. We automatically build the high-quality 3D model of an object by accurately extracting the 3D multiview features from the CAD model with the object-precision method instead of the existing image-precision method. Precision of the features from the image-precision method is limited to the precision of the image resolution and varies with the view distance and view-up vector. Since we exploit the object-precision method to extract the 3D multiview features, the precision of the features is equal to the precision at which the object is defined in the CAD and is independent of the view distance and view-up vector.     

Integrating Automated Range Registration with Multiview Geometry for the Photorealistic Modeling of Large-Scale Scenes

The photorealistic modeling of large-scale scenes, such as urban structures, requires a fusion of range sensing technology and traditional digital photography. This paper presents a system that integrates automated 3D-to-3D and 2D-to-3D registration techniques, with multiview geometry for the photorealistic modeling of urban scenes. The 3D range scans are registered using our automated 3D-to-3D registration method that matches 3D features (linear or circular) in the range images. A subset of the 2D photographs are then aligned with the 3D model using our automated 2D-to-3D registration algorithm that matches linear features between the range scans and the photographs. Finally, the 2D photographs are used to generate a second 3D model of the scene that consists of a sparse 3D point cloud, produced by applying a multiview geometry (structure-from-motion) algorithm directly on a sequence of 2D photographs. The last part of this paper introduces a novel algorithm for automatically recovering the rotation, scale, and translation that best aligns the dense and sparse models. This alignment is necessary to enable the photographs to be optimally texture mapped onto the dense model. The contribution of this work is that it merges the benefits of multiview geometry with automated registration of 3D range scans to produce photorealistic models with minimal human interaction. We present results from experiments in large-scale urban scenes.     

Non-rigid 3D shape tracking from multiview video

We present a fast and efficient non-rigid shape tracking method for modeling dynamic 3D objects from multiview video. Starting from an initial mesh representation, the shape of a dynamic object is tracked over time, both in geometry and topology, based on multiview silhouette and 3D scene flow information. The mesh representation of each frame is obtained by deforming the mesh representation of the previous frame towards the optimal surface defined by the time-varying multiview silhouette information with the aid of 3D scene flow vectors. The whole time-varying shape is then represented as a mesh sequence which can efficiently be encoded in terms of restructuring and topological operations, and small-scale vertex displacements along with the initial model. The proposed method has the ability to deal with dynamic objects that may undergo non-rigid transformations and topological changes. The time-varying mesh representations of such non-rigid shapes, which are not necessarily of fixed connectivity, can successfully be tracked thanks to restructuring and topological operations employed in our deformation scheme. We demonstrate the performance of the proposed method both on real and synthetic sequences.     

Fusing multiview and photometric stereo for 3D reconstruction under uncalibrated illumination

We propose a method to obtain a complete and accurate 3D model from multiview images captured under a variety of unknown illuminations. Based on recent results showing that for Lambertian objects, general illumination can be approximated well using low-order spherical harmonics, we develop a robust alternating approach to recover surface normals. Surface normals are initialized using a multi-illumination multiview stereo algorithm, then refined using a robust alternating optimization method based on the l(1) metric. Erroneous normal estimates are detected using a shape prior. Finally, the computed normals are used to improve the preliminary 3D model. The reconstruction system achieves watertight and robust 3D reconstruction while neither requiring manual interactions nor imposing any constraints on the illumination. Experimental results on both real world and synthetic data show that the technique can acquire accurate 3D models for Lambertian surfaces, and even tolerates small violations of the Lambertian assumption.     

Whole-body modelling of people from multiview images to populate virtual worlds

In this paper a new technique is introduced for automatically building recognisable, moving 3D models of individual people. A set of multiview colour images of a person is captured from the front, sides and back by one or more cameras. Model-based reconstruction of shape from silhouettes is used to transform a standard 3D generic humanoid model to approximate a person's shape and anatomical structure. Realistic appearance is achieved by colour texture mapping from the multiview images. The results show the reconstruction of a realistic 3D facsimile of the person suitable for animation in a virtual world. The system is inexpensive and is reliable for large variations in shape, size and clothing. This is the first approach to achieve realistic model capture for clothed people and automatic reconstruction of animated models. A commercial system based on this approach has recently been used to capture thousands of models of the general public.     

Depth image‐based rendering for multiview generation

Abstract— Techniques for 3‐D display have evolved from stereoscopic 3‐D systems to multiview 3‐D systems, which provide images corresponding to different viewpoints. Currently, new technology is required for application in multiview display systems that use input‐source formats such as 2‐D images to generate virtual‐view images of multiple viewpoints. Due to the changes in viewpoints, occlusion regions of the original image become disoccluded, resulting in problems related to the restoration of output image information that is not contained in the input image. In this paper, a method for generating multiview images through a two‐step process is proposed: (1) depth‐map refinement and (2) disoccluded‐area estimation and restoration. The first step, depth‐map processing, removes depth‐map noise, compensates for mismatches between RGB and depth, and preserves the boundaries and object shapes. The second step, disoccluded‐area estimation and restoration, predicts the disoccluded area by using disparity and restores information about the area by using information about neighboring frames that are most similar to the occlusion area. Finally, multiview rendering generates virtual‐view images by using a directional rendering algorithm with boundary blending.     

Direct light field rendering without 2D image generation

Rapid developments in 3D display technologies have enabled consumers to enjoy 3D environments in an increasingly immersive manner through various display systems such as stereoscopic, multiview, and light field displays. However, there is a corresponding increase in the complexity of the conventional multiview rendering process in the attempt to achieve a sufficient level of reality, which may hinder the further commercial viability of 3D display products based on such a conventional approach. This paper proposes a novel method, the so‐called direct light field rendering, which can compose the display 3D panel image without reconstructing all the multiview images beforehand. Interpreting the 3D display as sampling in the light field domain, we attempt to directly compute only the necessary samples, not the entire light fields or multiview images. Our proposed algorithm involves the solving of linear systems of two variables, thereby requiring remarkably low computational complexities. Experimental results show that the computation time and memory usage remain as little as 12% and 1% of those required by the conventional one.     

A multiview 3D modeling system based on stereo vision techniques

This paper introduces a stereo vision system to automatically generate 3D models of real objects. 3D model generation is based on the merging of multiview range images obtained from a digital stereo camera. Stereo images obtained from the camera are rectified, and a correlation-based stereo matching technique reconstructs range images from them. A turntable stage is also employed to obtain multiple range images of the objects. To register range images into a common coordinate system automatically, we introduce and calibrate a turntable coordinate system with respect to the camera coordinate system. After the registration of multiview range images, a 3D model is reconstructed using a volumetric integration technique. Error analysis on turntable calibration and 3D model reconstruction shows the accuracy of our 3D modeling system.Received: 2 August 2003, Accepted: 20 September 2004, Published online: 25 February 2005 Correspondence to: S.Y. Park     

Three‐dimensional lenticular display synthetic image rendering based on light field acquisition

Crosstalk is a critical defect affecting image quality in multiview lenticular 3D displays. Existing optimization methods require tedious computations and device‐specific optical measurements, and results are often suboptimal. We propose a new method, on the basis of light field acquisition and optimization, for crosstalk reduction in super multiview displays. Theory and algorithms were developed, and experimental validation results showed superior performance.     

Multiview 3D reconstruction of the archaeological site at Weymouth from image series

Multiview (n-view or multiple view) 3D reconstruction is the computationally complex process by which a full 3D model is derived from a series of overlapping images. It is based on research in the field of computer vision, which in turn relies on older methods from photogrammetry. This report presents a multiview reconstruction tool chain composed from various freely available, open source components and a practical application example in the form of a 3D model of an archaeological site.