基于DaVinci~(TM)的360°全景泊车影像系统的设计与实现

全景泊车影像系统通过安装在车身前后左右的4个超广角摄像头实时采集车辆四周的影像,经过图像处理器矫正变换和全景拼接后,形成一幅车辆四周的360°全景俯视图,并实时传送到中控台的显示设备上,驾驶员坐在车中即可看到车辆所处的位置以及车辆周围的障碍物,有效减少刮蹭、碰撞、陷落等事故的发生。系统采用TI公司的低成本高性能达芬奇DSP处理器TMS320DM6437和四路视频解码器TVP5158构成系统的硬件核心,以鱼眼矫正和鸟瞰变换算法以及全景拼接技术构成系统的软件核心,实现了具有高分辨率的画质和流畅处理速度的360°全景泊车影像系统。     

一种视频检测车辆位置违章的几何方法

针对交通视觉监控系统中普遍存在的遮挡与三维信息缺失问题,用一种三维矩形近似描述模型对车辆建模,基于此模型推导出在自遮挡和交互遮挡情况下,车辆整体轮廓、底部轮廓和单一底边的恢复规则和方法.提出将车辆运动视为其车辆底部在道路平面上的二维共面运动,通过分析车辆底部与道路标线的相对位置关系,得到位置违章的两个检测判据与检测算法.实验结果表明,该几何模型能很好的逼近车辆底边,有效的解决了遮挡的影响;该位置违章检测算法避免了以往质心检测判据与区域判据的缺陷,检测效果很好.     

基于OpenGL的三维图形显示在精细油藏描述中的应用

现实中,所有的物体都是三维的。但是在计算机中,所有的三维物体必须以二维平面图像的形式表现出来。将物体的三维坐标转换到计算机的像素位置,需要经过几何变换、投影变换、裁剪变换、视口变换等操作,才能正确显示出储层的三维图像。     

基于全景深度图像的汽车外形重建方法

将全景深度图像与虚拟现实建模语言VRML的特点有机结合起来,实现了由深度图像到三维模型的快速重建及车身外形的多细节层次描述。该算法在网格均匀细化基础上,结合图像处理方法,能有效处理车身外形的孔洞部分,且较准确地反映车身外形。利用所得到的三维VRML模型,可方便地进行模型交互修改,并实时显示;在汽车外形概念设计和用户个性化外形定制系统的应用中,对VRML模型的建立提出了一种新方法。     

3维卡通水与物体交互作用的动画建模

为了生成水与物体交互作用的卡通动画,提出一个混合式的3维卡通水模型。先构造出复杂的各种卡通水波模型,然后在2维工作区上对它们进行结构上的组合并映射到3维水面上进行绘制;障碍物在3维水面上的覆盖区域被检测出来之后,将其逆映射到2维工作区并在工作区内实现流水波形和障碍物所在区域的碰撞检测,根据碰撞检测结果触发障碍物附近的激起浪花波形。该方法的特点在于既表现了卡通流水与障碍物的碰撞,又保持了手工绘画的艺术感。此外,用户还可以方便地对波形的形态、位置、速度等进行设置与调控。系统利用GPU（图形处理器）硬件处理能力实现了对3维卡通水与物体交互的实时绘制。     

基于全景深度图像的汽车外形重建方法

将全景深度图像与虚拟现实建模语言VRML的特点有机结合起来,实现了由深度图像到三维模型的快速重建及车身外形的多细节层次描述.该算法在网格均匀细化基础上,结合图像处理方法,能有效处理车身外形的孔洞部分,且较准确地反映车身外形.利用所得到的三维VRML模型,可方便地进行模型交互修改,并实时显示;在汽车外形概念设计和用户个性化外形定制系统的应用中,对VRML模型的建立提出了一种新方法.     

一种基于图像的大型车辆车身长度自动测量方法

针对传统汽车尺寸测量技术在实际应用环境限制下的不足,提出一种基于图像的大型车辆车身长度测量方法。利用图像分割技术和基于图像边缘特征的匹配方法完成车身侧面全景图像拼接,并利用双目测距原理计算出车辆与相机间的距离,在此基础上,根据透视投影原理计算出最终的车身长度。实验结果表明,该方法可以很好地在受限的测量环境中自动、快速、准确地测量出大型车辆车身长度。     

三维点云中的二维标记检测

特征检测在物体识别、数据配准等应用中具有至关重要的作用。同一场景中不同采集数据的配准和融合,必须已知或者估算不同数据中的共同特征对应点。然而,许多场景缺少有效对应特征点。解决该问题的一种有效的方法是在场景中添加标记以增加特征。文章提出一种在只含有位置信息的三维点云中自动检测二维标记的方法。该方法首先在三维场景添加黑色圆形薄纸片作为二维标记,利用区域增长法将获取的三维场景的点云数据分割成不同类别,然后基于随机抽样一致性算法的扩展方法依次对分割后的点云进行形状拟合,最后通过检测形状检测该二维标记。该方法能够有效地检测出三维场景中的二维标记,并避免了遮挡、形变等问题,为缺少特征的场景提供了简单可行的特征,可广泛应用于数据配准、物体识别、物体追踪、三维重建等领域。     

2D-3D转换:由二维线画图生成三维复杂零部件

在计算机辅助概念设计和计算机图形学领域,利用二维线画图输入可以方便用户有效地创建新的复杂物体。根据输入的二维特征线画图,提出了一种有效的三维重建方法来生成包含带状面、内嵌圆柱面和空心多边形面等的三维复杂零部件物体。在假设输入的二维线画图是三维待重建物体的简单平行投影的前提下,首先引进用户手绘输入二维特征线画图的若干规则,有助于实现对二维线画图的解释以及对几何物体拓扑结构的有效识别。然后,利用立方角理论精确计算复杂零部件物体各顶点的三维坐标。最后,根据二维线画图的拓扑结构信息,高效重建出复杂零部件物体,并以三角网格的形式表示。实验结果表明,该方法能够精确、高效地生成诸如机械零部件等的三维复杂形状。     

计算机三维物体实体组建方法的研究

在计算机绘图和三维图像显示,例如激光扫描共焦显微图像、CT图像、MRI图像等的绘制和显示中,三维物体的组建是必不可少的。目前,三维物体的组建都是基于二维物体组建的基础之上。二维物体组建是基于连通性进行二维连通区域检出的,因而三维物体的组建速度比较慢。为此,文章提出一种新方法:围线积分法区域标号和链接表法三维叠片,用于三维图像中三维物体实体的组建。这种方法的基本原理是在三维二值图像中,先采用围线积分法区域标号,组建二维物体切片,再采用链接表法三维叠片,由二维物体切片组建三维实体。这种方法的优点是组建速度比较快。     

A flexible vehicle surround view camera system by central-around coordinate mapping model

The surround view camera system is an emerging driving assistant technology that can assist drivers in parking by providing top-down view of surrounding situations. Such a system usually consists of four wide-angle or fish-eye cameras that mounted around the vehicle, and a bird-eye view is synthesized from images of these cameras. Commonly there are two fundamental problems for the surround view synthesis, geometric alignment and image synthesis. Geometric alignment performs fish-eye calibration and computes the image perspective transformation between the bird-eye view and images from the surrounding cameras. Image synthesis technique dedicates to seamless stitch between adjacent views and color balancing. In this paper, we propose a flexible central-around coordinate mapping (CACM) model for vehicle surround view synthesis. The CACM model calculates perspective transformation between a top-view central camera coordinate and the around camera coordinates by a marker point based method. With the transformation matrices, we could generate the pixel point mapping relationship between the bird-eye view and images of the surrounding cameras. After geometric alignment, an image fusion method based on distance weighting is adopted for seamless stitch, and an effective overlapping region brightness optimization method is proposed for color balancing. Both the seamless stitch and color balancing can be easily operated by using two types of weight coefficient under the framework of the CACM model. Experimental results show that the proposed approaches could provide a high-performance surround view camera system.

     

光栅投影测量系统三维形貌拼接技术研究

针对尺寸较大或型面复杂的被测物形貌的测量,提出了一种基于投影仪投射标记点和全局控制点的三维形貌拼接方案。方案充分利用光栅投影测量系统的优势,以拼接相机坐标系为中介,将被测物表面在投影系统视觉传感器坐标系下的多视点云坐标转换到全局坐标系下,实现了将投影系统视觉传感器在不同位置、不同角度的测量数据统一到全局坐标系,完成拼接。该方案避免了人工标记点的粘贴,保持了被测物表面的原有形貌,提高了测量效率,同时克服了基于相邻图像重叠拼接中的误差累积问题。此方案方法操作简单,原理可行,精度可满足要求。实验结果表明:拼接的X,Y,Z坐标均方根误差分别为:0.056 mm、0.023 mm、0.165 mm,测量系统的绝对误差为0.33 mm。     

基于动力学模型的汽车制动稳定性虚拟展示

现有3D引擎的物理模型不能真实反映车辆制动时的运动状态。为此,提出一种汽车制动稳定性虚拟展示系统。建立汽车动力学模型,包括四轮车辆模型和车轮轮胎模型,利用上层仿真软件对动力学模型进行运算和虚拟场景渲染,给出车轮状态和虚拟仪表的展现方法,并基于3D引擎设计虚拟展现系统。实验结果表明,该系统能同时观测整车及车轮的运行状态,实时再现制动过程中车轮抱死、车身横摆侧滑的行为,其动力学模型能够满足虚拟展现对画面渲染的实时性、连续性要求。     

限制失真的网格参数化方法

针对当前网格参数化效率较低、映射失真较严重的问题，提出一种限制失真的网格参数化方法。首先，预处理原始网格模型。输入原3D网格模型，采用Half-Edge数据结构来重新组织网格并切割网格模型产生相应的切缝；构建Tutte映射把3D网格映射到一个2D凸多边形域，即构建2D网格模型。然后，进行限制失真的网格参数化计算。将Tutte映射后的2D网格模型作为限制失真计算的初始数据，建立相对于原3D模型网格的失真度量函数；求得该度量函数的最小值点，即为映射后的网格坐标集合；将映射后的网格作为限制失真映射的输入网格，设定迭代终止条件，循环迭代直至迭代结束，得到收敛的最优网格坐标；在计算映射失真度时，针对等距映射失真采用Dirichlet能量函数度量，针对共形映射失真采用尽可能等距（MIPS）能量函数度量；在求解映射失真度量函数的最小值点时采用代理函数法结合组合牛顿法的最优解方法。最终，实现了该方法并开发了一个原型系统。在原型系统中，分别设计了限制等距失真和限制共形失真的网格参数化实验，对程序执行时间和失真能量下降情况进行了统计和对比，提供了相应的纹理映射效果展示。实验数据表明，所提出的方法执行效率高、映射失真能量下降快，最优值收敛质量稳定；纹理映射时纹理着色均匀、布局紧致、线条均匀，符合实际应用的标准。     

Distortion visualization techniques for 3D coherent sets: A case study of 3D building property units

In the fields of 3D cadastre and 3D property management system, numerous building property objects are adjacent as primary property units assemble into a 3D coherent set. During visualization process of the coherent set, occlusion, obscure, mazy spatial relationships and relative location relationships among the units of the coherent set cause difficulty in observing and understanding the set and its units. Common 3D objects viewing method, such as rotation and navigation obtaining desired visualization effects through adjusting the view angle and position of the camera's field of view, provides weak interactive experience and orientation control for the coherent set because of the neighbour relationships of the 3D objects inside the set. In this paper, a novel method is proposed to solve the prior problems with two basic distortion methods based on “focus + context” theory. The coherent set is first discretized into individual objects and changed them locations according to linear or orthogonal function, while keeping their relative location and dual topological relationships. To maintain both global context awareness (topology and locations) of 3D coherent set and highlight effect of the focus 3D building property object, three evaluation indexes are adopted to assess the corresponding distortion results. A case study based on the real clustered 3D property in Shenzhen was conducted to evaluate the performance of distortion functions, the result shows that the method proposed in this article can not only expand the visual area of focused object and create a clear line of sight (LOS) to the focal object previously obscured, but also maintain verticality and proximity in some degree to facilitate understand the spatial occupation and distribution of whole coherent objects.     

基于投影技术的虚拟文物展示系统

为了更好地将投影映射技术应用于博物馆的数字展览,获得高质量的投影效果,设计出一套具有真实感的3D效果和高保真外观的三维数字文物展示系统.该系统利用机械旋转的实物模型和真实文物的图像,将多投影映射技术和光学透视显示相结合,采用几何学与辐射定标方法,在不发生透视畸变的情况下,将高质量的文物纹理正确地投射到动态的3D文物模型投影面上,增加投影效果和投影内容的自由度.为了评估该系统在一般博物馆环境光的影响和周围物阴影遮挡等问题,利用不同强度的光线对该系统投影区和展示区进行了测试,证明了该系统对周围环境光具有较强的鲁棒性和博物馆环境下的部署潜力,使博物馆数字文物展示内容变得更为丰富.     

Hand-held 3D scanning based on coarse and fine registration of multiple range images

A hand-held 3D scanning technique is proposed to reconstruct 3D models of real objects. A sequence of range images captured from a hand-held stereo camera is automatically registered to a reference coordinate system. The automated scanning process consists of two states, coarse and fine registration. At the beginning, scanning process starts at the fine registration state. A fast and accurate registration refinement technique is used to align range images in a pair-wise manner. If the refinement technique fails, the process changes to the coarse registration state. A feature-based coarse registration technique is proposed to find correspondences between the last successful frame and the current frame. If the coarse registration successes, the process returns to the fine registration state again. A fast point-to-plane refinement technique is employed to do shape-based registration. After the shape-based alignment, a texture-based refinement technique matches texture features to enhance visual appearance of the reconstructed models. Through a graphic and video display, a human operator adjusts the pose of the camera to change the view of the next acquisition. Experimental results show that 3D models of real objects are reconstructed from sequences of range images.     

Floating autostereoscopic display with in situ interaction

Floating three‐dimensional (3D) display implements direct interaction between human hands and virtual 3D images, which offers natural and effective augmented reality interaction. In this study, we propose a novel floating autostereoscopic display, combining head tracking lenticular display with an image projection system, to offer the observers with an accurate 3D image floating in midair without any optical elements between observers and the virtual 3D image. Combined with a gesture recognition device, the proposed system can achieve in situ augmented reality interaction with the floating 3D image. A distortion correction method is developed to achieve 3D display with accurate spatial information. Moreover, a coordinate calibration method is designed to improve the accuracy in the in situ interaction. Experiments were performed to prove the feasibility of the proposed system, and the good results show the potential of human‐computer interaction in medicine and life sciences.     

Approach to Nonrigid Body Metamorphosis UsingGeneralized Morph-translation

An approach of morphing by decomposing two objects into sets of individual convex sub objects respectively and contructing the mapping between two sets is presented The Minkvski addition of two convex sub-objects according to their mapping ralationship is calculated, then all the Minkovski additions are combined to obtain the final result. Nonrigid body motion can be divided into nonrigid body metamorphosis and rigid body rotation A novel method for describing nonrigid body motion based on generalized morph-translation is proposed. This method can solve the metamorphosis problem of two non-homotopic objects. Experiments show tha this method can generate natural, high quality metamorphosis results with simple computation. This method can also be used in interpolation between two keyframes in 2D and 3D computer animation automatically.     

A study on the 3D position estimation of ventricular borders extracted from 2D echocardiography data

We study on the reconstruction of 3D left ventricle(LV) using only 2D echocardiography data and information on apical long-axis views. Especially, this paper focuses on determining the 3D position of LV contours extracted from 2D echocardiography images. First we mathematically model the relationship between LV contours on the apical views and their corresponding 3D positions. The relationship is expressed as a linear equation in which the right-hand side is the measured data consisting of all the LV contour points on each view and the coefficient matrix is an unknown matrix that transforms the unknown 3D positions into contour points on their related apical view, with distance and orthogonality conditions on the coefficient matrix and the 3D positions. Next we consider a non-convex constrained minimization problem to determine the coefficient matrix and the 3D positions. To solve this minimization problem, we adopt two block coordinate descent method with a solver in OPTI for quadratically constrained quadratic program. For validating the proposed method, some numerical experiments are performed with synthetic data. The experimental results show that the proposed model is promising and available for real echocardiographydata.