Reconstruction of dynamic 3D scene based on visual hull and view morphing

In this paper, we propose a new method that processes multiple synchronized video sequences and generates 3D rendering of dynamic objects in the video. It exploits an efficient image‐based reconstruction scheme that constructs and shades 3D models of objects from silhouette images by combining image‐based visual hull and view morphing. The proposed hybrid method improves the speed and the quality of the previous visual hull sampling methods. We designed and implemented a system based on this method which is relatively low cost and does not require any special hardware or specific environment. Copyright © 2003 John Wiley & Sons, Ltd.     

Real-time exploration and photorealistic reconstruction of large natural environments

This paper presents a hybrid (geometry- and image-based) framework suitable for providing photorealistic walkthroughs of large, complex outdoor scenes, based only on a small set of real images from the scene. To this end, a novel data representation of a 3D scene is proposed, which is called morphable 3D panoramas. Motion is assumed to be taking place along a predefined path of the 3D environment and the input to the system is a sparse set of stereoscopic views at certain positions (key positions) along that path (one view per position). An approximate local 3D model is constructed from each view, capable of capturing the photometric and geometric properties of the scene only locally. Then, during the rendering process, a continuous morphing (both photometric as well as geometric) takes place between successive local 3D models, using what we call a ‘morphable 3D model’. For the estimation of the photometric morphing, a robust algorithm capable of extracting a dense field of 2D correspondences between wide-baseline images is used, whereas, for the geometric morphing, a novel method of computing 3D correspondences between local models is proposed. In this way, a physically valid morphing is always produced, which is thus kept transparent from the user. Moreover, a highly optimized rendering path is used during morphing. Thanks to the use of appropriate pixel and vertex shaders, this rendering path can be run fully in 3D graphics hardware and thus allows for high frame rates. Our system can be extended to handle multiple stereoscopic views (and therefore multiple local models) per key position of the path (related by a camera rotation). In this case, one local 3D panorama (per key position) is constructed, comprising all local 3D models therein, and so a ‘morphable 3D panorama’ is now used during the rendering process. For handling the geometric consistency of each 3D panorama, a technique which is based on solving a partial differential equation is adopted. The effectiveness of our framework is demonstrated by using it for the 3D visual reconstruction of the Samaria Gorge in Crete.     

实景空间中虚拟对象嵌入技术研究

实景空间是以实景图像为素材构造出的具有三维操纵能力的虚拟空间,增强现实技术可以把计算机产生的虚拟物体或其他信息合成到用户看到的真实场景中。该文主要讨论如何在实景空间中嵌入计算机生成的虚拟对象。首先介绍了实景空间的概念和模型,然后着重探讨了虚拟对象与实景空间的合成方法,主要解决合成中的几何一致性和光照一致性问题。     

基于图像的视点变换方程

多年来,造型技术模拟自然界物体形状生成的图像都显得过于规则化和“人工化”。有鉴于此,提出了基于图像的虚拟现实。而完善的虚拟现实系统应该支持多自由度的观察,如视点的移动。视点变换就是求视点移动后原始图像变换生成的新视图。以前给出的变换公式都是在同一坐标系下视点移动后生成的视图。此文给出了在任意坐标系下视点移动后生成新视图的公式,以及具体推导过程。     

Virtual view synthesis of people from multiple view video sequences

This paper addresses the synthesis of novel views of people from multiple view video. We consider the target area of the multiple camera 3D Virtual Studio for broadcast production with the requirement for free-viewpoint video synthesis for a virtual camera with the same quality as captured video. A framework is introduced for view-dependent optimisation of reconstructed surface shape to align multiple captured images with sub-pixel accuracy for rendering novel views. View-dependent shape optimisation combines multiple view stereo and silhouette constraints to robustly estimate correspondence between images in the presence of visual ambiguities such as uniform surface regions, self-occlusion, and camera calibration error. Free-viewpoint rendering of video sequences of people achieves a visual quality comparable to the captured video images. Experimental evaluation demonstrates that this approach overcomes limitations of previous stereo- and silhouette-based approaches to rendering novel views of moving people.     

Novel View Synthesis Of Transparent Object From a Single Image

We propose a method for converting a single image of a transparent object into multi-view photo that enables users observing the object from multiple new angles, without inputting any 3D shape. The complex light paths formed by refraction and reflection makes it challenging to compute the lighting effects of transparent objects from a new angle. We construct an encoder–decoder network for normal reconstruction and texture extraction, which enables synthesizing novel views of transparent object from a set of new views and new environment maps using only one RGB image. By simultaneously considering the optical transmission and perspective variation, our network learns the characteristics of optical transmission and the change of perspective as guidance to the conversion from RGB colours to surface normals. A texture extraction subnetwork is proposed to alleviate the contour loss phenomenon during normal map generation. We test our method using 3D objects within and without our training data, including real 3D objects that exists in our lab, and completely new environment maps that we take using our phones. The results show that our method performs better on view synthesis of transparent objects in complex scenes using only a single-view image.     

森林气候实时建模方法的研究

提出了一种半透明体建模方法：对采集的图像学习生成过程纹理,对纹理进行边界合成得到划分了颜色区域的图像,对颜色区域边界进行扫描,勾勒出图像的轮廓线网格,并根据当前颜色为每个网格边界赋颜色值,根据网格的颜色值生成三维模型。实验证明这种动态景物的建模方法能够满足虚拟场景实时绘制的要求,而且具有很好的鲁棒性和连续性。     

Live 3D Video in Soccer Stadium

This paper proposes a method to realize a 3D video system that can capture video data from multiple cameras, reconstruct 3D models, transmit 3D video streams via the network, and display them on remote PCs. All processes are done in real time. We represent a player with a simplified 3D model consisting of a single plane and a live video texture extracted from multiple cameras. This 3D model is simple enough to be transmitted via a network. A prototype system has been developed and tested at actual soccer stadiums. A 3D video of a typical soccer scene, which includes more than a dozen players, was processed at video rate and transmitted to remote PCs through the internet at 15–24 frames per second.     

LAMP: 3D layered, adaptive-resolution, and multi-perspective panorama—a new scene representation

A compact visual representation, called the 3D layered, adaptive-resolution, and multi-perspective panorama (LAMP), is proposed for representing large-scale 3D scenes with large variations of depths and obvious occlusions. Two kinds of 3D LAMP representations are proposed: the relief-like LAMP and the image-based LAMP. Both types of LAMPs concisely represent almost all the information from a long image sequence. Methods to construct LAMP representations from video sequences with dominant translation are provided. The relief-like LAMP is basically a single extended multi-perspective panoramic view image. Each pixel has a pair of texture and depth values, but each pixel may also have multiple pairs of texture-depth values to represent occlusion in layers, in addition to adaptive resolution changing with depth. The image-based LAMP, on the other hand, consists of a set of multi-perspective layers, each of which has a pair of 2D texture and depth maps, but with adaptive time-sampling scales depending on depths of scene points. Several examples of 3D LAMP construction for real image sequences are given. The 3D LAMP is a concise and powerful representation for image-based rendering.     

面向视频感知的静电力触觉渲染方法

针对视觉障碍的人获取视频等数字媒体信息受限的问题, 为扩展视频等数字媒体信息的触觉感知通道,提出一种面向视频感知的静电力触觉渲染方法。首先,采用基于像素点的视频帧处理算法,根据手指触摸位置获取当前视频帧的目标像素点,然后将目标像素点彩色信息从RGB模型转换为HSI模型,利用像素点色调分量来映射静电力激励信号频率参量,结合像素点亮度和饱和度分量来映射静电力激励信号幅度参量,合成静电力触觉激励信号,实现对实时视频的触觉渲染和感知。最后,设计动态色彩感知实验和亮度辨识感知实验,结果表明,该方法可实现对视频中物体信息的触觉感知,动态识别平均正确率达90.6%,色彩辨识平均正确率达69.4%,亮度辨识平均正确率达80.0%,所提方法能有效提取视频中的动态特征信息,增强视频触觉渲染的实时性。     

城市视频实景地图构建初探

城市视频实景地图兼具地图立体空间、视频时间4维度层面信息统一表达能力，对于我国城市立体监控系统构建、互联网地图产品发展，以及未来实景3维中国建设战略实施具有重要意义和应用价值。为引起更多研究者进行探索，对城市视频实景地图构建方法、技术及其应用前景进行讨论。从增强虚拟环境技术（AVE）角度出发，对融合全景视频与地理3维模型构建城市视频实景地图涉及的全景摄像机标定、全景视频空间配准及视频纹理映射、实时渲染系列技术、方法进行了梳理。经过分析得出：1）适合传统“针孔”模型的摄像机标定、影像空间配准理论和方法，需根据全景摄像机球面投影模型进行拓展；2）适合静态纹理的大规模3D场景渲染LOD（levels of detail）技术和策略，需结合视频传输带宽限制、高帧率特点进行技术创新。城市视频实景地图构建是一项值得重视的崭新课题，将有力促进互联网、人工智能前沿技术发展，有望给相关行业带来万亿级市场机遇。     

Multi‐view reconstruction of dynamic real‐world objects and their integration in augmented and virtual reality applications

We present a flexible system for high‐quality three‐dimensional reconstruction of dynamic real‐world objects based on a modular multi‐camera capture setup. The proposed algorithmic pipeline aims at the acquisition and digitization of natural and realistic representations of real people that can be easily integrated into augmented and virtual reality applications. In this context, we discuss the reduction of mesh complexity as one of the key challenges for visualizing reconstructed three‐dimensional content with augmented and virtual reality glasses and demonstrate different fields of application.     

Toward cinematizing our daily lives

We introduce a cinematographic video production system to create movie-like attractive footage from our indoor daily life. Since the system is designed for ordinary users in non-studio environments, it is composed of standard hardware components, provides a simple interface, and works in near real-time of 5 ~ 6 frames/sec. The proposed system reconstructs a visual hull from acquired multiple videos and then generates final videos from the model by referring to the camera shots used in film-making. The proposed method utilizes “Reliability” to compensate for errors that may have occurred in non-studio environments and to produce the most natural scene from the reconstructed model. By using a virtual camera control system, even non-experts can easily convert the 3D model to movies that look as if they were created by experienced filmmakers.

On-line Free-viewpoint Video： From Single to Multiple View Rendering

In recent years, many image-based rendering techniques have advanced from static to dynamic scenes and thus become video-based rendering （VBR） methods. But actually, only a few of them can render new views on-line. We present a new VBR system that creates new views of a live dynamic scene. This system provides high quality images and does not require any background subtraction. Our method follows a plane-sweep approach and reaches real-time rendering using consumer graphic hardware, graphics processing unit （GPU）. Only one computer is used for both acquisition and rendering. The video stream acquisition is performed by at least 3 webcams. We propose an additional video stream management that extends the number of webcams to 10 or more. These considerations make our system low-cost and hence accessible for everyone. We also present an adaptation of our plane-sweep method to create simultaneously multiple views of the scene in real-time. Our system is especially designed for stereovision using autostereoscopic displays. The new views are computed from 4 webcams connected to a computer and are compressed in order to be transfered to a mobile phone. Using GPU programming, our method provides up to 16 images of the scene in real-time. The use of both GPU and CPU makes this method work on only one consumer grade computer.     

彩色视频的四维矩阵离散余弦变换编码

为了在高信噪比条件下获得对彩色视频的高倍压缩 ,提出了 4维矩阵及 4维矩阵离散余弦变换理论 ,并将该理论应用于彩色视频编码 .基于 4维矩阵离散余弦变换的彩色视频编码方法将彩色视频的多个帧放在一个统一的数学模型 (即 ,4维矩阵 )中考虑 ,利用 4维矩阵离散余弦变换去除其间的各种相关性 ,并通过矢量量化对变换系数进行压缩编码 .其方法可以同时全面利用彩色视频图象相邻像素间、彩色空间 Y、U、V 3分量间 ,以及视频图象相邻帧之间的相关性 .实验结果证明 ,对可视电话和视频会议等应用中的彩色视频序列图象 ,利用该方法可在高信噪比条件下获得较高压缩比的编码效果     

基于坐标逆映射的增强型车辆三维全景影像

当前最先进的车辆三维全景影像虽然可以较好地对车身周边环境进行三维立体的拟真显示,但仍然会对车身近处的三维物体造成显示畸变,极大地影响显示效果、降低实用性。针对该问题,提出一种增强型车辆三维全景影像的合成方法。首先利用YOLOv4网络检测出车辆及行人在图像中的位置,之后基于坐标升维逆映射将检测出的物体位置升维映射至世界坐标系下,最后将三维模型渲染在相应的逆映射位置上来代替显示畸变的三维物体,从而给驾驶员提供有效的周边物体位置信息。实验结果表明,所提方法生成的增强型车辆三维全景影像具有很好的实时性和显示效果,能够有效解决当前车辆三维全景影像的显示缺陷。     

Line‐Drawing Video Stylization

We present a method to automatically convert videos and CG animations to stylized animated line drawings. Using a data‐driven approach, the animated drawings can follow the sketching style of a specific artist. Given an input video, we first extract edges from the video frames and vectorize them to curves. The curves are matched to strokes from an artist's library, while following the artist's stroke distribution and characteristics. The key challenge in this process is to match the large number of curves in the frames over time, despite topological and geometric changes, allowing to maintain temporal coherence in the output animation. We solve this problem using constrained optimization to build correspondences between tracked points and create smooth sheets over time. These sheets are then replaced with strokes from the artist's database to render the final animation. We evaluate our tracking algorithm on various examples and show stylized animation results based on various artists.     

Real-time 3D shape reconstruction, dynamic 3D mesh deformation, and high fidelity visualization for 3D video

3D video [IEEE Multimedia (1997) 18] is the ultimate image media recording dynamic visual events in the real world as is; it records time varying 3D object shape with high fidelity surface properties (i.e., color and texture). Its applications cover wide varieties of personal and social human activities: entertainment (e.g., 3D game and 3D TV), education (e.g., 3D animal picture books), sports (e.g., sport performance analysis), medicine (e.g., 3D surgery monitoring), culture (e.g., 3D archive of traditional dances), and so on. In this paper, we propose: (1) a PC cluster system for real-time reconstruction of dynamic 3D object action from multi-view video images, (2) a deformable 3D mesh model for reconstructing the accurate dynamic 3D object shape, and (3) an algorithm of rendering natural-looking texture on the 3D object surface from the multi-view video images. Experimental results with quantitative performance evaluations demonstrate the effectiveness of these methods in generating high fidelity 3D video from multi-view video images.     

Stereo‐Consistent Contours in Object Space

Notebook scribbles, art or technical illustrations—line drawings are a simplistic method to visually communicate information. Automated line drawings often originate from virtual 3D models, but one cannot trivially experience their three‐dimensionality. This paper introduces a novel concept to produce stereo‐consistent line drawings of virtual 3D objects. Some contour lines do not only depend on an objects geometry, but also on the position of the observer. To accomplish consistency between multiple view positions, our approach exploits geometrical characteristics of 3D surfaces in object space. Established techniques for stereo‐consistent line drawings operate on rendered pixel images. In contrast, our pipeline operates in object space using vector geometry, which yields many advantages: The position of the final viewpoint(s) is flexible within a certain window even after the contour generation, e.g. a stereoscopic image pair is only one possible application. Such windows can be concatenated to simulate contours observed from an arbitrary camera path. Various types of popular contour generators can be handled equivalently, occlusions are natively supported and stylization based on geometry characteristics is also easily possible.