多视觉环境下联合多约束的三维目标体重建

提出了一种联合多种约束条件的体元重建方法。首先将场景空间离散为体元,并从多视获取的二维图像中提取目标轮廓信息;其次利用侧影轮廓约束及颜色一致性约束,恢复目标三维信息;针对重建模型存在漂浮体元和毛刺现象,提出加入平滑约束解决该问题;最后提出模型修复算法对模型表面空洞进行填补,解决重建模型空洞问题。实验结果表明,该方法可重建颜色纹理信息准确的目标外形,且模型光滑细腻,表面空洞得到有效填补。     

基于多分辨率实体的三维仿真系统研究

针对现代仿真系统对作战实体的多层次、高分辨粒度的应用需求,提出了基于多分辨率实体的战场三维仿真系统的总体结构,设计了系统的主要功能,给出了多分辨率实体三维建模与简化、实体模型库维护管理以及实体间分辨率匹配等关键技术途径与算法,并以坦克交战可视化仿真为例,分析了多分辨率实体建模及系统的集成方法,为基于多分辨实体的高精度、多层次战场三维仿真系统的研究提供了一种可行的技术途径。     

粒子群与改进的鲍威尔算法相结合的多分辨率三维医学图像配准

为克服传统基于互信息的多模医学图像配准算法容易陷入局部最优的问题,提出了一种改进的多分辨率三维医学图像配准算法.该算法通过高斯滤波将三维医学图像进行多尺度化,形成多分辨率图像金字塔,以Mattes互信息作为配准框架的相似性测度.在图像金字塔的低分辨率层使用粒子群优化算法进行全局变换参数的搜索,然后以全局变换参数作为高分辨率层配准的初始参数,并以鲍威尔优化算法进行优化,完成最终的三维医学图像配准.实验结果表明,改进的算法不仅使待配准两幅图像空间位置对齐,而且较传统互信息算法提高了配准精度,鲁棒性更强,有效地解决了基于互信息的配准算法陷入局部最优的可能.     

3D visualization of tomographic volume data using the generalized voxel model

Multi-slice images obtained from computer tomography and magnetic resonance imaging represent a 3D image volume. For its visualization we use a raycasting algorithm working on a gray-scale voxel data model. This model is extended by additional attributes such as membership to an organ or a second imaging modality (generalized voxel model). It is shown that the combination of different surface-rendering algorithms together with cutting and transparent display allow a realistic visualization of the human anatomy.The investigations were supported in part by the Deutsche Forschungsgemeinschaft and the Werner Otto Foundation, Hamburg.     

3D mapping of underwater caves

Wakulla Springs-a group of deep, underground, water-filled caves south of Tallahassee, FL, USA-is an example where mapping has proved challenging. The Wakulla 2 expedition of the US Deep Caving Team Inc. had one primary goal-to automatically build the first fully 3D cave map. To make the map, divers had to survive the hostile environment. The divers' attention mostly focuses on staying alive, so the more automatic the surveying, the better. The critical piece of equipment for the Wakulla 2 expedition was the Digital Wall Mapper (DWM). The device was designed specifically for the project to gather survey data to make the 3D map. 32 sonar transducers were spirally arrayed around the nose of the 2-m long, 150-kg instrument. Thus, four times a second, the DWM sends and receives 32 equally spaced radial readings. The distance to the walls was important but not useful unless we knew the DWM's exact position and orientation. To record this information, we used an inertial measurement unit (IMU), which is located in the center of the DWM     

3D textured model encryption via 3D Lu chaotic mapping

In the emerging Virtual/Augmented Reality (VR/AR) era, three dimensional (3D) content will be popularized just as images and videos today. The security and privacy of these 3D contents should be taken into consideration. 3D contents contain surface models and solid models. Surface models include point clouds, meshes and textured models. Previous work mainly focused on the encryption of solid models, point clouds and meshes. This work focuses on the most complicated 3D textured model. We propose a 3D Lu chaotic mapping based encryption method for 3D textured models. We encrypt the vertices, polygons, and textures of 3D models separately using the 3D Lu chaotic mapping. Then the encrypted vertices, polygons and textures are composited together to form the final encrypted 3D textured model. The experimental results reveal that our method can encrypt and decrypt 3D textured models correctly. Furthermore, typical statistic and brute-force attacks can be resisted by the proposed method.     

Platform independent optimisation of multi-resolution 3D content to enable universal media access

Flurries of terminals with large differences in terminal capabilities currently consume information and multi-media content. Their different processing capabilities make it challenging to guarantee satisfactory quality in all possible situations. This paper proposes a systematic methodology for interactive 3D graphics applications to adapt the complexity of the content automatically to the terminal’s available resources. Our contribution is an off-line/online partitioned optimisation that increases the visual quality with respect to previous work at the same rendering cost, while the overhead of the optimisation is minimal.     

Probabilistic voxel mapping using an adaptive confidence measure of stereo matching

In this paper, we describe a probabilistic voxel mapping algorithm using an adaptive confidence measure of stereo matching. Most of the 3D mapping algorithms based on stereo matching usually generate a map formed by point cloud. There are many reconstruction errors. The reconstruction errors are due to stereo reconstruction error factors such as calibration errors, stereo matching errors, and triangulation errors. A point cloud map with reconstruction errors cannot accurately represent structures of environments and needs large memory capacity. To solve these problems, we focused on the confidence of stereo matching and probabilistic representation. For evaluation of stereo matching, we propose an adaptive confidence measure that is suitable for outdoor environments. The confidence of stereo matching can be reflected in the probability of restoring structures. For probabilistic representation, we propose a probabilistic voxel mapping algorithm. The proposed probabilistic voxel map is a more reliable representation of environments than the commonly used voxel map that just contains the occupancy information. We test the proposed confidence measure and probabilistic voxel mapping algorithm in outdoor environments.     

3D mapping of an interactive synthetic environment

Traditional geospatial information systems (GIS) use geographically referenced data to produce highly accurate digital maps. These two-dimensional maps include well-recognized symbols that represent features such as mountains, forests, buildings, and transportation networks. Although this flat view provides an excellent means of orienting the user to the general nature and location of the geographic features for a given area, it does not provide the full experiential value that comes from immersion within a 3D environment. The authors, working in conjunction with the University of New Orleans' Computer Science Department, developed a 3D-GIS to assist the US Marine Corps with mission preparation and rehearsal. It also provides on-site awareness during actual field operations in urban areas. Going beyond presenting stereoscopic views of an area or merely applying photo textures to highly simplified geometric shapes, they created an environment that replicates its real-world counterpart by including detailed 3D objects. The article details the design considerations they faced as well as the implementation and structural overview for the entire system     

Surface mapping brain function on 3D models

A flexible graphics system for displaying functional and anatomic data on arbitrary collections of surfaces on or within the brain is presented. The system makes it possible to show complex, convoluted surfaces with the shading cues necessary to understand their shapes; to vary viewpoint, object position, illumination, and perspective easily; to show multiple-objects in one view, with or without transparency, in order to examine internal surfaces and intersecting objects in relation to each other; and to superimpose quantitative information on biological or otherwise defined surfaces anywhere within the volume, thus furthering understanding of both quantitative and positional information in its global context. These display techniques are applied to a new form of biological surface model, the removed surface. The surface-removal method creates a set of surfaces internal to a given object, so that, given a specified distance, every point on the created surfaces is equidistant from the surface of the enclosing object. The method is based on thresholding a derived scalar field, the minimum distance field. Models made by this method have applications in 3-D neurobiology and provide an alternative to cutaways for viewing patterns of internal functional activity     

Detailed 3D human body reconstruction from multi-view images combining voxel super-resolution and learned implicit representation

Applied Intelligence - The task of reconstructing detailed 3D human body models from images is interesting but challenging in computer vision due to the high freedom of human bodies. This work...     

3D cartoon face generation by local deformation mapping

We present a data-driven method for automatically generating a 3D cartoon of a real 3D face. Given a sparse set of 3D real faces and their corresponding cartoon faces modeled by an artist, our method models the face in each subspace as the deformation of its nearby exemplars and learn a mapping between the deformations defined by the real faces and their cartoon counterparts. To reduce the exemplars needed for learning, we regress a collection of linear mappings defined locally in both face geometry and identity spaces and develop a progressive scheme for users to gradually add new exemplars for training. At runtime, our method first finds the nearby exemplars of an input real face and then constructs the result cartoon face from the corresponding cartoon faces of the nearby real face exemplars and the local deformations mapped from the real face subspace. Our method greatly simplifies the cartoon generation process by learning artistic styles from a sparse set of exemplars. We validate the efficiency and effectiveness of our method by applying it to faces of different facial features. Results demonstrate that our method not only preserves the artistic style of the exemplars, but also keeps the unique facial geometric features of different identities.     

3D clipping algorithm for feature mapping across domains

This paper describes an algorithm based on 3D clipping for mapping feature models across domains. The problem is motivated by the need to identify feature models corresponding to different domains. Feature mapping (also referred to as feature conversion) involves obtaining a feature model in one domain given a feature model in another. This is in contrast to feature extraction which works from the boundary representation of the part. Most techniques for feature mapping have focused on obtaining negative feature models only. We propose an algorithm that can convert a feature model with mixed features (both positive and negative) to a feature model containing either only positive or only negative features.The input to the algorithm is a feature model in one domain. The algorithm for mapping this model to another feature model is based on classification of faces of features in the model and 3D clipping. 3D clipping refers to the splitting of a solid by a surface. The feature mapping process involves three major steps. In the first step, faces forming the features in the input model are classified with respect to one another. The spatial arrangement of faces is used next to derive the dependency relationship amongst features in the input model and a Feature Relationship Graph (FRG) is constructed. In the second step, using the FRG, features are clustered and interactions between features (if any) are resolved. In the final step, the 3D clipping algorithm is used to determine the volumes corresponding to the features in the target domain. These volumes are then classified to identify the features for obtaining the feature model in the target domain. Multiple feature sets (where possible) can be obtained by varying the sequence of faces used for clipping. Results of implementation are presented.     

A methodology for 3D geological mapping and implementation

Multimedia Tools and Applications - Using 3D visualization models to exhibit geological structure has become a trend in geological studies. Compared to 2D geological mapping, 3D geological mapping...     

Learning with multi-resolution overlapping communities

A recent surge of participatory web and social media has created a new laboratory for studying human relations and collective behavior on an unprecedented scale. In this work, we study the predictive power of social connections to determine the preferences or behaviors of individuals such as whether a user supports a certain political view, whether one likes a product, whether she would like to vote for a presidential candidate, etc. Since an actor is likely to participate in multiple different communities with each regulating the actor’s behavior in varying degrees, and a natural hierarchy might exist between these communities, we propose to zoom into a network at multiple different resolutions and determine which communities reflect a targeted behavior. We develop an efficient algorithm to extract a hierarchy of overlapping communities. Empirical results on social media networks demonstrate the promising potential of the proposed approach in real-world applications.     

纹理映射在模型优化中的应用

三维模型的构建是虚拟现实及视景仿真系统中最基本、最重要的组成部分之一。构建三维模型需考虑到场景浏览的真实感与实时性,因而需要建立一个最优化的可视化模型。本文比较了在虚拟现实系统中模型优化的方法,采用了纹理映射代替多边形建模创建高效真实感模型的优化手段,着重介绍了颜色纹理和凹凸纹理的相关理论和方法,并应用于视景仿真系统中,极大的提高了实时性,并保证了真实感。     

基于Radon变换的颅骨多分辨率身份识别

颅骨以其生理位置的隐蔽性和解剖结构的相对稳定性,近来被提出作为一种特殊的生物特征并加以识别研究。准确、高效的识别是人们追求的主要目标。基于此,首先对活体颅骨的X线照片进行二值化处理,再使用Radon变换将二维的图像转换为一维信号,最后对一维信号进行小波多分辨率分析。同时为进一步提高识别效率,提出半分处理和方向特征组方法,实现了在多尺度下准确、快速实时的身份识别。试验结果表明该方法是有效可行并适合于非活体颅骨身份鉴定和识别。     

Real-time face tracking and recognition by sparse eigentracker with associative mapping to 3D shape

This paper proposes a novel framework of real-time face tracking and recognition by combining two eigen-based methods. The first method is a novel extension of eigenface called augmented eigenface and the second method is a sparse 3D eigentemplate tracker controlled by a particle filter. The augmented eigenface is an eigenface augmented by an associative mapping to 3D shape that is specified by a set of volumetric face models. This paper discusses how to make up the augmented eigenface and how it can be used for inference of 3D shape from partial images. The associative mapping is also generalized to subspace-to-one mappings to cover photometric image changes for a fixed shape. A novel technique, called photometric adjustment, is introduced for simple implementation of associative mapping when an image subspace should be combined to a shape. The sparse 3D eigentemplate tracker is an extension of the 3D template tracker proposed by Oka et al. In combination with the augmented eigenface, the sparse 3D eigentemplate tracker facilitates real-time 3D tracking and recognition when a monocular image sequence is provided. In the tracking, sparse 3D eigentemplate is updated by the augmented eigenface while face pose is estimated by the sparse eigentracker. Since the augmented eigenface is constructed on the conventional eigenfaces, face identification and expression recognition are also accomplished efficiently during the tracking. In the experiment, an augmented eigenface was constructed from 25 faces where 24 images were taken in different lighting conditions for each face. Experimental results show that the augmented eigenface works with the 3D eigentemplate tracker for real-time tracking and recognition.     

3D PEE mapping based reversible data hiding for color images

Multimedia Tools and Applications - The performance of prediction-error expansion (PEE) for reversible data hiding (RDH) is excellent. 2D and 3D PEE has a great improvement than the conventional...