Circularity — a new principle underlying the design of accurate edge orientation operators

Currently available fast edge detection operators are reviewed. Their rationale is studied with particular reference to the estimation of angular orientation of edges. The idea of ‘circular’ edge detection operators is developed, and used to explain the surprising accuracy of the Sobel operator. A family of circular operators is designed for use in neighbourhoods of various sizes, and general ideas on edge operator design are developed. The concept of ‘closed bands’ of pixels for making neighbourhoods close to circular should be widely applicable in digital image analysis, not just in the ambit of fast edge detection.     

工业CT断层序列图像三维重建的实现

文中对ICT序列断层图像进行三维结构的重建和显示。先对图像进行预处理，去掉空气环，然后再利用Matlab功能强大的函数用体绘制方法进行断层序列图像的三维重建，对某一工业CT机提供的实测数据进行了三维重建，实验结果比较理想。     

基于Canny算子图像边缘检测的改进方法

针对传统Canny算子在边缘检测中的不足,提出一种基于Canny算子图像边缘检测的改进方法。传统Canny算子的高低阈值一般是人为地设定固定值,这容易造成虚假边缘。对此,利用最小交叉熵计算Canny算子的高低阈值,得到理想的边缘后,利用数学形态学对结果进行后处理。实验结果表明,改进后的算法具有自适应性,抑制噪声能力较强,有效地提高了边缘检测的鲁棒性。     

3D object perception using gradient descent

A new algorithm is presented for interpreting two-dimensional (2D) line drawings as three-dimensional (3D) objects without models. Even though no explicit models or additional heuristics are included, the algorithm tends to reach the same 3D interpretations of 2D line drawings that humans do. The algorithm explicitly calculates the partial derivatives of Marill's Minimum Standard Deviation of Angles (MSDA) with respect to all adjustable parameters, and follows this gradient to minimize SDA. For an image with lines meeting atm points formingn angles, the gradient descent algorithm requiresO(n) time to adjust all the points, while Marill's method requiredO(mn) time to do so. Experimental results on various line drawing objects show that this gradient descent algorithm running on a Macintosh II is one to two orders of magnitude faster than the MSDA algorithm running on a Symbolics, while still giving comparable results.     

多视角三维人脸识别中的特征提取

针对二维人脸识别系统在姿态发生较大变化就难以识别的问题,利用三维人脸数据姿态不变性的特征,提出了一个基于方向最大值的方法来估计鼻尖点,同时也给出姿态的角度.用子空间表示的鼻子轮廓模型被用来选择鼻尖点的最可行的候选点.另外,利用SUSAN算子提取边缘,并与方向积分投影等方法结合,快速准确的定位内外眼角点和嘴角点.实验证明该方法可以保证达到和手工自动标定特征点相差无几的准确率.     

Recognition of 3D facial expression dynamics

In this paper we propose a method that exploits 3D motion-based features between frames of 3D facial geometry sequences for dynamic facial expression recognition. An expressive sequence is modelled to contain an onset followed by an apex and an offset. Feature selection methods are applied in order to extract features for each of the onset and offset segments of the expression. These features are then used to train GentleBoost classifiers and build a Hidden Markov Model in order to model the full temporal dynamics of the expression. The proposed fully automatic system was employed on the BU-4DFE database for distinguishing between the six universal expressions: Happy, Sad, Angry, Disgust, Surprise and Fear. Comparisons with a similar 2D system based on the motion extracted from facial intensity images was also performed. The attained results suggest that the use of the 3D information does indeed improve the recognition accuracy when compared to the 2D data in a fully automatic manner.     

Evaluating 2D and 3D geovisualisations for basic spatial assessment

This study investigates the use of 2D and 3D presentations of maps for the assessment of distances in a geographical context. Different types of 3D representations have been studied: A weak 3D visualisation that provides static monocular depth cues and a strong 3D visualisation that uses stereoscopic and kinetic depth cues. Two controlled experiments were conducted to test hypotheses regarding subjects’ efficiency in visually identifying the shortest distance among a set of market locations in a map. As a general result, we found that participants were able to correctly identify shortest distances when the difference to potential alternatives was sufficiently large, but performance decreased systematically when this difference decreased. Noticeable differences emerged for the investigated visualisation conditions. Participants in this study were equally efficient when using a weak 3D representation and a 2D representation. When the strong 3D visualisation was employed, they reported visual discomfort and tasks solved were significantly less correct. Presentations of intrinsic 2D content (maps) in 3D context did not, in this study, benefit from cues provided by a strong 3D visualisation and are adequately implemented using a weak 3D visualisation.     

基于Matlab的颅面三维重构技术

介绍了一种以Matlab为工具实现颅面三维重构的方法。给出了利用该方法处理医学图像、构造体数据集和三维重构的全过程。提出了完成医学图像三维重构的技术路线、方法和步骤。为医学图像的三维可视化技术提供了一种新的可能。     

图像边缘检测方法研究

边缘检测是图像处理和模式识别领域的基本课题。阐述了传统的边缘检测方法——微分算子法和现代的一些边缘检测方法——小波分析、形态学、分形、模糊学、人工智能、遗传算法等,分析了以上各种算法在图像边缘检测中的发展状况及其优缺点。为了直观地看出各种算法的效果,给出了用一些常用算法对同一幅目标图像进行边缘提取的结果。最后提出在实践中应根据待解决问题的特点和要求决定采用何种方法。     

Web-Based 3D Geometry Model Retrieval

Due to the popularity of the Internet, multimedia searching is becoming more and more an important research area. It allows us to search the Internet for media objects by specifying some feature criteria or providing sample objects. Although a lot of work has been conducted on searching images, videos and audio, there has been very limited work on searching 3D object models and most of the proposed methods only show the performance of the proposed method, without a comparison with other methods. In this paper, we survey some representative work in this area. We show how they are implemented and compare their performances with each other using a common geometry database. We also propose the Haar wavelets method for 3D model matching. This method is simple to implement, has a very good retrieval performance, and small feature size, as demonstrated in our experiments.     

Visual discomfort of stereoscopic 3D videos: Influence of 3D motion

Visual discomfort is one of the most frequent complaints of the viewers while watching 3D images and videos. Large disparity and large amount of motion are two main causes of visual discomfort. To quantify this influence, three objectives are set in this paper. The first one is the comparative analysis on the influence of different types of motion, i.e., static stereoscopic image, planar motion and in-depth motion, on visual discomfort. The second one is the investigation on the influence factors for each motion type, for example, the disparity offset, the disparity amplitude and velocity. The third one is to propose an objective model for visual discomfort. Thirty-six synthetic stereoscopic video stimuli with different types of motion are used in this study. In the subjective test, an efficient paired comparison method called Adaptive Square Design (ASD) was used to reduce the number of comparisons for each observer and keep the results reliable. The experimental results showed that motion does not always induce more visual discomfort than static conditions. The in-depth motion generally induces more visual discomfort than the planar motion. The relative disparity between the foreground and the background, and the motion velocity are identified as main factors for visual discomfort. According to the subjective results, an objective model for comparing visual discomfort induced by different types of motion is proposed which shows high correlation with the subjective perception.     

基于极限投影变换的3D模型检索

基于认知理论和投影理论,提出极限投影面积方法对三维模型进行坐标标准化:将模型不断绕过模型重心的基向量旋转,采集每次坐标面投影面积,在多次迭代后得到最大面积投影,用同样办法获得另一坐标面上的最小面积投影,建立模型的坐标系.实验结果表明:该方法标准化的坐标系处理对象范围宽,适用于网格模型、点云模型和各类曲面模型,针对模型噪声、简化、攻击等有很强的鲁棒性.经该方法标准化的三维模型在3个坐标面的投影作为模型的特征描述子,并在实验中为实验模型库建立了对应的特征描述子库,使得对模型检索转化为特征描述子间的比较检索.检索实验表明:该方法针对增加了特征描述子的模型库具有较快的检索速度;同时具有较强的鲁棒性,但检索的精度稍差.     

Efficient routing techniques in heterogeneous 3D Networks-on-Chip

Three-dimensional Networks-on-Chips (3D NoCs) have recently been proposed to address the on-chip communication demands of future highly dense 3D multi-core systems. Homogeneous 3D NoC topologies have many Through Silicon Vias (TSVs) which have a costly and complex manufacturing process. Also, 3D routers use more memory and are more power hungry than conventional 2D routers. Alternatively, heterogeneous 3D NoCs combine both the area and performance benefits of 2D and 3D static router architectures by using a limited number of TSVs. To improve the performance of heterogeneous 3D NoCs, we propose an adaptive router architecture which balances the traffic in such NoCs. Particularly, experimental results show that our proposed architecture significantly improves the performance up to 75% by replacing 2D static routers with adaptive 2D routers in heterogeneous 3D NoCs, while keeping the maximum clock frequency, power and energy consumption of the adaptive router nearly at the same level as the static router.     

碰撞检测在三维场景漫游中的研究与实现

碰撞检测是三维漫游中的一项重要功能。通过面向对象图形渲染引擎(OGRE)构建了一个模拟三维漫游系统,利用OgreNewt结合Newton库在系统中实现碰撞检测功能。碰撞检测包围盒均采用3DSMax创建,利用OgreNewt中的碰撞检测树解析,既保证了碰撞的精确性,又节省了编码工作量。适用于层次结构较复杂的三维场景的加载和碰撞检测。     

Towards precise real-time 3D difference detection for industrial applications

3D difference detection is the task to verify whether the 3D geometry of a real object exactly corresponds to a 3D model of this object. We present an approach for 3D difference detection with a hand-held depth camera. In contrast to previous approaches, with the presented approach geometric differences can be detected in real-time and from arbitrary viewpoints. The 3D difference detection accuracy is improved by two approaches: first, the precision of the depth camera's pose estimation is improved by coupling the depth camera with a high precision industrial measurement arm. Second, the influence of the depth measurement noise is reduced by integrating a 3D surface reconstruction algorithm. The effects of both enhancements are quantified by a ground-truth based quantitative evaluation, both for a time-of-flight (SwissRanger 4000) and a structured light depth camera (Kinect). With the proposed enhancements, differences of few millimeters can be detected from 1 m measurement distance.     

Horizon picking in 3D seismic data volumes

In this paper, we present an automatic horizon-picking algorithm, based on a surface detection technique, to detect horizons in 3D seismic data. The surface detection technique, and the use of 6-connectivity, allows us to detect fragments of horizons that are afterwards combined to form full horizons. The criteria of combining the fragments are similarity of orientation of the fragments, as expressed by their normal vectors, and proximity using 18-connectivity. The identified horizons are interrupted at faults, as required by the experts.Received: 16 August 2003, Accepted: 4 May 2004, Published online: 17 August 2004 Correspondence to: Maria Petrou     

Reshaping 3D facial scans for facial appearance modeling and 3D facial expression analysis

3D face scans have been widely used for face modeling and analysis. Due to the fact that face scans provide variable point clouds across frames, they may not capture complete facial data or miss point-to-point correspondences across various facial scans, thus causing difficulties to use such data for analysis. This paper presents an efficient approach to representing facial shapes from face scans through the reconstruction of face models based on regional information and a generic model. A new approach for 3D feature detection and a hybrid approach using two vertex mapping algorithms, displacement mapping and point-to-surface mapping, and a regional blending algorithm are proposed to reconstruct the facial surface detail. The resulting models can represent individual facial shapes consistently and adaptively, establishing facial point correspondences across individual models. The accuracy of the generated models is evaluated quantitatively. The applicability of the models is validated through the application of 3D facial expression recognition using the static 3DFE and dynamic 4DFE databases. A comparison with the state of the art has also been reported.     

基于Ogre3D的三维坦克游戏的设计与实现

为了实现一款游戏规划的需求,设计了一种基于Ogre3D的三维坦克游戏引擎基本框架结构及其核心模块,并具体给出了我方主战坦克、非玩家角色模块接口和控制算法以及基于脚本的引擎接口等关键技术的设计与实现.采用基于脚本的引擎接口设计使相关的游戏逻辑和游戏内容相分离,从而避免硬编码,提高了游戏的开发效率.最后以实例表明了该非玩家角色控制算法的可行性.