基于图象的室内虚拟漫游系统

基于图象的绘制（Image Based Rendering)作为一种全新的图形绘制方式,以其相对于传统几何绘制而言,具有高效实用的优点,近年来得到了研究人员越来越多的关注,但IBR技术仍存在一些主要难点,如图象的无缝拼接和实时漫游。针对此问题,开发了一个基于部分球面模型的室内虚拟漫游系统。该系统采用自动匹配和人机交互相结合的方法,可以无缝地将多幅照片拼接成一张全景图,同时采用一种改进的基于查找表的算法,实现了固定视点的实时漫游。     

一种圆柱形全景图生成新算法及其实现

利用基于图象的绘制(IBR)技术来建立具有真实感的虚拟环境是当前计算机图形学研究领域中的一项热门课题，也是虚拟现实技术中的关键技术。它以简单的图象合成代替基于三维几何的建模和渲染，加快了画面的显示速度，是建立特定三维场景的一种高效率的方法。基于这种方法，我们提出了一种生成圆柱形全景图的新算法，它通过快速查找
相邻两幅图象的匹配区域而实现图象的无缝拼接，建立圆柱形全景图。本算法计算速度快，效率高，能生成逼真的全景图。文章的最后给出了基于这种算法生成的部分全景图图实例。     

基于垂直边缘处理的全景图像的拼接

基于图像的绘制技术是虚拟现实中建立虚拟环境的重要方法，而全景图像是基于图像绘制的关键。该文提出了一种基于图像垂直边缘处理的全景图像拼接方法，通过边缘检测方法锐化图像的主要垂直边缘，增强图像的匹配特征，实现了图像有效的自动拼接。     

光场渲染技术的软件实现

IBR(Image Based Rendering)作为计算机图形学一个重要领域,已有大量的技术提出以重现先前绘制的或实际的图像,如:通过扭曲输入图像在图像间插值,它们利用场景的深度信息或图像间的相关性在多幅图像间实现。光场渲染是在不需要图像的深度信息或相关性的条件下,通过相机把在任何一个位置,任何一个视角观察到的场景的样子拍摄下来,然后在渲染的过程中,对于每个视点简单地合成那些有用的图像,从而最终得到新的图像。在本文中我们将研究一套将光场渲染技术在虚拟展示中加以应用的软件实现解决方案。     

全向立体成像系统场景深度估计

基于单相机双抛物面反射镜设计了一种共轴结构的折反射全向立体成像装置,给出了针对相应展开柱面全景立体图像对深度估计的应点匹配方法,最后通过3D Max构造相应虚拟装置和虚拟场景进行了仿真实验,初步证明了该结构设计和对应深度估计方法的有效性。     

Face posture estimation using eigen analysis on an IBR (image based rendered) database

In this paper, we present a novel representation of the human face for estimating the orientation of the human head in a two dimensional intensity image. The method combines the use of the much familiar eigenvalue based dissimilarity measure with image based rendering. There are two main components of the algorithm described here: the offline hierarchical image database generation and organization, and the online pose estimation stage. The synthetic images of the subject's face are automatically generated offline, for a large set of pose parameter values, using an affine coordinate based image reprojection technique. The resulting database is formally called as the IBR (or image based rendered) database. This is followed by the hierarchical organization of the database, which is driven by the eigenvalue based dissimilarity measure between any two synthetic image pair. This hierarchically organized database is a detailed, yet structured, representation of the subject's face. During the pose estimation of a subject in an image, the eigenvalue based measure is invoked again to search the synthetic (IBR) image closest to the real image. This approach provides a relatively easy first step to narrow down the search space for complex feature detection and tracking algorithms in potential applications like virtual reality and video-teleconferencing applications.     

An algorithm to estimate the crown patterns of diamonds based on machine vision

In this paper, we describe an algorithm that estimates the cut quality of the crown patterns of diamonds based on machine vision. To accurately extract the features of the edges of diamonds in complicated diamond images, a strategy based on multi-scale decomposition is employed. Using an enhanced Eigen space method, the orientation of the diamond can be roughly estimated. From the traditional least squares distance method, we derive the conditions of the least squares distance weighted by wavelet transform modulus. Then, the problem of diamond-edge feature extraction is transformed into a virtual control process through building a virtual girder truss model (VGTM) and a virtual attraction field (VAF). Using two stages, rough feature extraction and refined feature extraction, all the desired diamond edges can be accurately located by the virtual beams in the VGTM. Then, the cut quality of the diamond’s crown pattern can be effectively estimated according to the feature extraction results. The algorithm is demonstrated with a real machine vision system.     

Developing a mobile robot for transport applications in the hospital domain

We have been developing MKR (Muratec Keio Robot), an autonomous omni-directional mobile transfer robot system for hospital applications. This robot has a wagon truck to transfer luggage, important specimens, and other materials. This study proposes an obstacle collision avoidance technique for the wagon truck pulling robot which uses an omni-directional wheel system as a safe movement technology. Moreover, this paper proposes a method to reach the goal along a global path computed by path planning without colliding with static and dynamic obstacles. The method is based on virtual potential fields. Several modules with different prediction times are processed in parallel to change the robot response according to its relative velocity and position with respect to the obstacles. The virtual force calculated from each potential field is used to generate the velocity command. Some experiments were carried out to verify the performance of the proposed method. From the experimental results in a hospital it was confirmed that the robot can move along its global path, and reach the goal without colliding with static and moving obstacles.     

基于全景图像的拼接算法研究

IBR技术不仅可以弥补传统基于几何绘制技术的不足,而且能给出更丰富的图像显示.论文从工程实际应用的角度出发,提出并实现了一种图像拼接的新方法.该方法即可用于全景控件图像的拼接,也可用于普通图像的拼接.试验证明,此方法在全景图像的生成中具有自动拼接、效率高等优点.     

全景摄像系统中展开图像的电子稳像方法研究*

深入分析和研究了全景图像的解算算法与稳像的实现方法,提出了全景摄像系统的稳像方法——基于灰度投影的电子稳像算法。该系统的硬件由全景装置、CCD、图像采集卡和计算机构成,软件编程基于DirectShow平台,通过VC++实现。通过对结果的分析表明,该算法的设计具有快速、准确的特征,是实现全景摄像系统的电子稳像的一种切实可行的方法。     

基于IBR的三维重建新方法

在研究普通的平面图像的基础上,基于图像渲染(IBR)提出了一种新的建立立体模型的方式。能对普通的平面单幅图像进行特征点提取,从而半自动地生成所需要的立体效果。该方法直接从图像中提取信息,渲染出具有照片真实感的模型。实验结果表明,利用该系统渲染的三维模型准确真实,能够满足虚拟现实等应用的需要。     

A generic structure-from-motion framework

We introduce a generic structure-from-motion approach based on a previously introduced, highly general imaging model, where cameras are modeled as possibly unconstrained sets of projection rays. This allows to describe most existing camera types including pinhole cameras, sensors with radial or more general distortions, catadioptric cameras (central or non-central), etc. We introduce a structure-from-motion approach for this general imaging model, that allows to reconstruct scenes from calibrated images, possibly taken by cameras of different types (cross-camera scenarios). Structure-from-motion is naturally handled via camera independent ray intersection problems, solved via linear or simple polynomial equations. We also propose two approaches for obtaining optimal solutions using bundle adjustment, where camera motion, calibration and 3D point coordinates are refined simultaneously. The proposed methods are evaluated via experiments on two cross-camera scenarios—a pinhole used together with an omni-directional camera and a stereo system used with an omni-directional camera.     

一种与模型无关的全向视觉系统标定方法

传统的全向视觉系统标定方法假设研究对象满足单视点成像模型且全向反射镜面各向同性,而在实际应用中上述假设往往并不成立,这会对标定精度带来很大的影响。针对全向视觉系统成像特点设计了一种新的与模型无关的标定方法,不需要研究对象满足上述约束,适用于对各种折反射式全向视觉系统的标定,具有较高的精度。将其应用于NuBot足球机器人全向视觉系统的标定后,较大地提高了机器人基于全向视觉的自定位精度,验证了标定方法的有效性和实用性。     

Coverage-enhancing approach in multimedia directional sensor networks for smart transportation

Smart transportation has a significantly impact on city management and city planning, which has received extensive attentions from academic and industrial communities. Different from omni-directional sensing system, as a directional sensing system, the multimedia-directional sensor network holds the special coverage scheme, which is usually used for smart cities, smart transportation, and harsh environment surveillance, for instance, nuclear-pollution regions where are inhospitable for people. This paper advances Virtual Stream Artificial Fish-swarm based Coverage-Enhancing Algorithm (VSAFCEA) as a coverage-enhancing means in multimedia directional sensor networks. Firstly, a concept of virtual streams, based on traditional artificial fish-swarm algorithm, is proposed. Then, the traditional behaviors of fishes in artificial fish-swarm algorithm are modified and expanded with several new behaviors. Finally, the presented VSAFCEA is adopted for coverage-enhancing issue in the situation of directional sensor networks with rotational direction-adjustable model. With a sequence of steps of artificial fishes in virtual stream, the presented VSAFCEA can figure out the approximation to the highest area coverage rate. Based on comparison of these simulation results (results of presented VSAFCEA and that of other typical coverage-enhancing ways in directional sensor networks), the conclusion can be drawn that VSAFCEA could attain higher area coverage rate of directional sensor networks with fewer iterative computing times.

     

基于立体折反射全向成像的柱面全景深度估算

针对立体视觉原理的新型立体折反射全向成像系统结构设计和面向立体柱面全景像对的局域灰度相关对应点快速匹配算法,从捕获的全向市体影像中提取有效深度信息,用于辅助全向视频分析处理中的对象检测和跟踪.采用单相机和两个不同参数的抛物面型反射镜构造了一种共轴结构的折反射全向立体成像装置,捕获的存在一定视差的原始全向立体像对被投影展开为立体柱面全景像对,而后通过特定对应点匹配算法提取稠密的深度信息.对应点匹配算法采用局部区域灰度相关的算了,并充分利用了双向匹配和柱面全景的外极线约束来提高匹配的速度和准确度.仿真实验有效恢复了场景深度信息,证明了整套装置结构设计及深度估计方法的有效性.     

基于粒子群优化和互信息量的全景图拼接算法

利用基于图像的绘制技术来构建虚拟空间是当前虚拟现实领域中的一项热门课题,而全景图的拼接又是基于图像的绘制技术中的重要研究内容之一,简单的图像合成代替传统的基于三维几何的建模和渲染.提出一种基于粒子群优化(PSO)和互信息量(MI)的全景图拼接算法,首先采用粒子群优化算法寻找包含足够多特征的模板区域,然后利用互信息量实现全景图像的拼接.算法不需要手工指定特征点,可自动对一组图像进行无缝拼接.实验结果表明算法对全景图的拼接具有良好的效果.它不但提高了渲染速度,而且能够有效地克服图像旋转对拼接的影响,是一种快速实用的全景图拼接算法.     

Virtual 3D City Model for Navigation in Urban Areas

In this paper, we propose to study the integration of a new source of a priori information, which is the virtual 3D city model. We study this integration for two tasks: vehicles geo-localization and obstacles detection. A virtual 3D city model is a realistic representation of the evolution environment of a vehicle. It is a database of geographical and textured 3D data. We describe an ego-localization method that combines measurements of a GPS (Global Positioning System) receiver, odometers, a gyrometer, a video camera and a virtual 3D city model. GPS is often consider as the main sensor for localization of vehicles. But, in urban areas, GPS is not precise or even can be unavailable. So, GPS data are fused with odometers and gyrometer measurements using an Unscented Kalman Filter (UKF). However, during long GPS unavailability, localization with only odometers and gyrometer drift. Thus, we propose a new observation of the location of the vehicle. This observation is based on the matching between the current image acquired by an on-board camera and the virtual 3D city model of the environment. We also propose an obstacle detection method based on the comparison between the image acquired by the on-board camera and the image extracted from the 3D model. The following principle is used: the image acquired by the on-board camera contains the possible dynamic obstacles whereas they are absent from the 3D model. The two proposed concepts are tested on real data.     

基于复值小波分解的图象拼合

图象拼合是一种基于图象的场景编码方法，它被很多基于图象的绘制IBR（image based rendering）系统采用，用来建立复杂的虚拟场景表示（例如，360°球面和柱面全景图、环境映照及高分辨率图象等）.基于复值小波多分辨率分解(Complex Wavelet Multiresolution Decomposition)提出了一种有效的图象拼合方法，它能同时地、逐步求精地对图象进行匹配和整合.首先，采用复值小波变换不仅可以保证全局优化的结果，还能够满足图象整合的规模不变和平移不变性.其次，基于多分辨     

虚拟城市可视化的研究与实现

“虚拟城市”技术是“数字地球”技术的重要组成部分,其研究戈键足怎样在Internet／Intranet上建立城市的虚拟可视化模型,是计算机科学、信息科学、地球科学、系统科学的有机融合。该文概括了“数字地球／虚拟城市”的基本概念,探讨基于Web、2DVR、3DVR和GIS柏结合的技术开发虚拟城市系统的新仿真模式及其关键技术和整体开发方案。提出了虚拟场景与外界交互的手段和方法,着重研究全景图、三维模型和网络动态交互技术结合实现交互式网络虚拟城市漫游的方法和实现过程,并给出了运行实例。通过该系统可以为城市规划、交通旅游等提供动态可视化显示的全新技术支持。     

Perception of Visual Artifacts in Image‐Based Rendering of Façades

Image‐based rendering (IBR) techniques allow users to create interactive 3D visualizations of scenes by taking a few snapshots. However, despite substantial progress in the field, the main barrier to better quality and more efficient IBR visualizations are several types of common, visually objectionable artifacts. These occur when scene geometry is approximate or viewpoints differ from the original shots, leading to parallax distortions, blurring, ghosting and popping errors that detract from the appearance of the scene. We argue that a better understanding of the causes and perceptual impact of these artifacts is the key to improving IBR methods. In this study we present a series of psychophysical experiments in which we systematically map out the perception of artifacts in IBR visualizations of façades as a function of the most common causes. We separate artifacts into different classes and measure how they impact visual appearance as a function of the number of images available, the geometry of the scene and the viewpoint. The results reveal a number of counter‐intuitive effects in the perception of artifacts. We summarize our results in terms of practical guidelines for improving existing and future IBR techniques.