基于轮廓线的三维网格曲面绘制

在融合了交互式轮廓绘制与网格造型技术的基础上,提出了一种快速三维网格曲面建模方法.根据绘制轮廓线的特征点分布,进行约束化三角网格剖分,提取二维轮廓线的骨架;选取骨架点和采样点投影到三维空间椭球曲面,并引入二面角原则,优化了空间离散数据点的三角化算法;最后缝合骨架点,获得三维网格曲面表示.实验结果表明了该算法的直观性、高效性.     

动态图的实时三维可视化的稳定性算法

提出动态图的实时三维可视化及其稳定性的问题。讨论在图的实时重画中兼顾动态稳定性和美观性的平衡策略。在三维静态美观布局算法的基础上，给出了动态图的若干实时三维可视化的稳定性算法，并分析了这些算法的时间性能和适用范围。算法已应用在若干可视化编程环境。     

An optimisation-based reconstruction engine for 3D modelling by sketching

An engine that automatically reconstructs a large variety of polyhedral, origami and wire-frame objects from single-view sketched drawings generated in a calligraphic interface is presented. The engine has two stages. An innovative optimisation-based line-drawing beautifier stage is introduced to convert rough sketches into tidied-up line drawings. Optimisation-based 3D reconstruction follows. Solutions are provided with which to overcome the problems associated with earlier approaches to optimisation-based 3D reconstruction. Suitable adjustments in the optimisation algorithms are proposed; simple and efficient tentative models are introduced, and current regularities are categorised in order to allow the objective function to be simplified. All three actions help to prevent local optima and improve the computational efficiency of optimisation-based 3D reconstruction. They all proved to be effective techniques to reduce the typical failure rate of optimisation approaches. A discussion of results that validate the engine is also provided.     

3D sketching for aesthetic design using fully free-form deformation features

This paper addresses the designers’ activity and in particular the way designers express an object shape in 2D sketches through character lines and how these lines form a basis for sketching shapes in 3D. The tools currently available in commercial CAS/CAD systems to manipulate the digital models are still not sufficiently suited to support design. In this paper, the so-called fully free-form deformation features (δ-F⁴) are introduced as a modelling method to take into account the curve-oriented stylists’ way of working. Both the advantages of a free-form surface deformation method and a feature-based approach are merged to define these high-level modelling entities allowing for a direct manipulation of surfaces through a limited number of intuitive parameters. Such features incorporate several characteristics designed to handle the uncertainties and/or inconsistencies of the designer's input during a sketching activity. In addition, a δ-F⁴ classification is proposed to enable a fast access to the desired shape according to its semantics and characteristics.     

A real-time 3D video analyzer for enhanced 3D audio–visual systems

Multimedia Systems - With the recent advent of three-dimensional (3D) sound home theater systems (HTS), more and more TV viewers are experiencing rich, immersive auditory presence at home. In this...     

High-quality and interactive animations of 3D time-varying vector fields

In this paper, we present an interactive texture-based method for visualizing three-dimensional unsteady vector fields. The visualization method uses a sparse and global representation of the flow, such that it does not suffer from the same perceptual issues as is the case for visualizing dense representations. The animation is made by injecting a collection of particles evenly distributed throughout the physical domain. These particles are then tracked along their path lines. At each time step, these particles are used as seed points to generate field lines using any vector field such as the velocity field or vorticity field. In this way, the animation shows the advection of particles while each frame in the animation shows the instantaneous vector field. In order to maintain a coherent particle density and to avoid clustering as time passes, we have developed a novel particle advection strategy which produces approximately evenly-spaced field lines at each time step. To improve rendering performance, we decouple the rendering stage from the preceding stages of the visualization method. This allows interactive exploration of multiple fields simultaneously, which sets the stage for a more complete analysis of the flow field. The final display is rendered using texture-based direct volume rendering     

3D自由曲线的绘制及智能修改算法

目前有关曲线及曲面的生成，大量的研究致力于从控点和节点的设置到曲率、切线矢量进一步精确的调整．然而其繁琐的几何参数计算、复杂的数学概念局限了设计者的使用，尤其他们更不适合早期的概念设计。此研究描述了基于笔输入的自由3D曲线的绘制．识别及直观的修改算法，此算法支持任意3D自由曲线的绘制，通过优化的采样机制自动识别产生适应性的B样条逼近曲线，它扩展了基于约束的曲线的生成方法，进而提出的简单的局部修改技术，引入了比例因子及区域间距的控制，有效的解决了曲线的光滑性，并通过实践检验了它们的高效性。     

基于Unity3 D的TEE实时模拟教学系统及其关键技术

以心脏围术期超声监测中发挥重要作用的经食管超声心动图为基础构建3D虚拟心脏,设计复杂图形快速切割算法和大规模视频实时加载方法,研发了基于Unity3D的TEE实时模拟教学系统,应用于临床住院医生模拟教学。该系统由模拟探头、模拟人、TEE模拟工作站构成。相比传统教学方法,模拟教学方法能够更好地培训学生在空间思维、手眼协调上的能力。     

一种三维头发的仿真方法

头发的仿真一直是计算机图形学中最具挑战性的问题之一.为了得到真实感的头发图像,运用了基于NURBS曲面的头发建模方法,由悬臂梁模型在头部曲面附近生成关键头发曲线;调节控制点改变曲线形状;构造NURBS曲面四边形带代替头发簇;在头部模型对头发进行光照渲染,可以使用纹理方法映射颜色纹理和alpha纹理以生成真实头发.最后碰撞检测与响应手段增强了头发动态感.仿真结果表明,上述方法可以获得具有比较逼真效果的头发图像.     

On-line modeling for real-time 3D target tracking

Model-based object tracking can provide autonomous mobile robotic systems with real-time 6-dof pose information, for example, enabling them to rendezvous with targets from a particular desired direction. Most existing model-based trackers, however, require the geometric model of the target to be known a priori, which may pose a practical problem in real-world environments. This paper presents a novel 3D modeler capable of building an approximate model of a target object on-line. The proposed technique rapidly constructs a 3D tessellated enveloping mesh and uses projective texture mapping to further model the target object’s surface features. Separation of the target object from background clutter is achieved via customizable interest filters. The resulting real-time object-tracking system was tested extensively via simulations and experiments.     

三维头发的建模方法研究

在现代的一些虚拟现实系统中,如模拟人体模型、游戏以及电影特技中需要对头发的真实感进行建模。虚拟现实的关键技术之一是对显示对象进行建模。因此,为解决由于头发数量庞大和其纤细的特性而使得头发图像生成过程缓慢复杂的问题,研究其相关技术具有重要价值。头发模拟的方法主要有：直接模拟、体积纹理模型、聚簇发束模型和宽松连接的粒子系统模型等。该文在现有的头发模拟方法分析的基础上,提出了一种基于粒子系统的头发模拟设计方法,从而在时间和计算开销上解决已有方法的不足。     

Physical sketching: Reconstruction and analysis of 3D objects from freehand sketches

When designing a 3D object, designers, engineers and teachers often begin investigating potential design tradeoffs by creating informal sketches. Ideally, these sketches-in combination with a variety of engineering analysis tools-would allow prediction of the object’s physical properties, especially those that affect the critical early design process. We introduce a pen-based system that reconstructs 3D spatial geometry from a single 2D freehand-sketch consisting of straight and curved lines in interactive time. Several optimization-based approaches to this problem have been proposed, but these generally have difficulty converging to an acceptable solution because the dimensionality of the search space is large. The primary contribution of this paper is a new reconstruction algorithm for orthographic projections of 3D wireframes. The algorithm reconstructs the depths of each vertex by exploiting geometric regularities among the graph lines in a reduced solution space, then optimizes a cost function over this space to recover the vertex depths. A second optimization algorithm is used to infer the 3D geometry of curved strokes once the vertex depths have been recovered. The proposed approach can recover the geometry of several objects with approximately 50 curved strokes in near interactive time. We also present an iterative, Tablet-PC-based design system that uses the proposed reconstruction algorithm to recover 3D objects from 2D orthographic sketches. The system allows the reconstructed objects to be subjected to two types of physical analysis, the results of which are superimposed directly on the sketch: a fast, kinematic simulation, and a complete finite-element-based static analysis. The object can quickly be modified in place using the pen-based interface according to the results of the analysis to allow for iterative design work. We demonstrate the system in action on a variety of early-stage design analyses.     

Automatic facial expression recognition in real-time from dynamic sequences of 3D face scans

In this paper, we present a fully-automatic and real-time approach for person-independent recognition of facial expressions from dynamic sequences of 3D face scans. In the proposed solution, first a set of 3D facial landmarks are automatically detected, then the local characteristics of the face in the neighborhoods of the facial landmarks and their mutual distances are used to model the facial deformation. Training two hidden Markov models for each facial expression to be recognized, and combining them to form a multiclass classifier, an average recognition rate of 79.4 % has been obtained for the 3D dynamic sequences showing the six prototypical facial expressions of the Binghamton University 4D Facial Expression database. Comparisons with competitor approaches on the same database show that our solution is able to obtain effective results with the advantage of being capable to process facial sequences in real-time.     

An automated technique for real-time production of lifelike animations of American Sign Language

Generating sentences from a library of signs implemented through a sparse set of key frames derived from the segmental structure of a phonetic model of ASL has the advantage of flexibility and efficiency, but lacks the lifelike detail of motion capture. These difficulties are compounded when faced with real-time generation and display. This paper describes a technique for automatically adding realism without the expense of manually animating the requisite detail. The new technique layers transparently over and modifies the primary motions dictated by the segmental model and does so with very little computational cost, enabling real-time production and display. The paper also discusses avatar optimizations that can lower the rendering overhead in real-time displays.     

From on-line sketching to 2D and 3D geometry: a system based on fuzzy knowledge

The paper describes the development of a fuzzy knowledge-based prototype system for conceptual design. This real time system is designed to infer user's sketching intentions, to segment sketched input and generate corresponding geometric primitives: straight lines, circles; arcs, ellipses, elliptical arcs, and B-spline curves. Topology information (connectivity, unitary constraints and pairwise constraints) is received dynamically from 2D sketched input and primitives. From the 2D topology information, a more accurate 2D geometry can be built up by applying a 2D geometric constraint solver. Subsequently, 3D geometry can be received feature by feature incrementally. Each feature can be recognised by inference knowledge in terms of matching its 2D primitive configurations and connection relationships. The system accepts not only sketched input, working as an automatic design tool, but also accepts user interactive input of both 2D primitives and special positional 3D primitives. This makes it easy and friendly to use. The system has been tested with a number of sketched inputs of 2D and 3D geometry.     

Stereophotogrammetric real-time 3D machine vision

Signal-processing algorithms often have to be strongly modified in case of hardware implementation. Especially, continuous real-time image processing at high speed is a challenging task. In this paper, a hardware/software codesign is applied to a stereophotogrammetric system. For calculations of a depth map, an optimized algorithm is implemented as a hierarchical parallel hardware solution. By dividing the measuring range into subranges and switching between them, real-time 3D measurements within a wide measuring range is possible. Object clustering and tracking are realized in a processor. The density distribution of the disparity in the depth map (disparity histogram) is used for object detection. A Kalman filter stabilizes the parameters of the results. The text was submitted by the authors in English.     

Stereophotogrammetric 3D real-time machine vision

Signal processing algorithms often have to be modified significantly for implementation in hardware. Continuous real-time image processing at high speed is a particularly challenging task. In this paper a hardware-software codesign is applied to a stereophotogrammetric system. To calculate the depth map, an optimized algorithm is implemented as a hierarchical-parallel hardware solution. By subdividing distances to objects and selecting them sequentially, we can apply 3D scanning and ranging over large distances. We designed processor-based object clustering and tracking functions. We can detect objects utilizing density distributions of disparities in the depth map (disparity histogram). Motion parameters of detected objects are stabilized by Kalman filters. The text was submitted by the authors in English. Michael Tornow was born in Magdeburg, Germany, in 1977. He received his diploma engineer degree (Dipl.-Ing.) in electrical engineering at the University of Magdeburg, Germany, in 2002. He is currently working on a PhD thesis focusing on hardware adapted image processing and vision based driver assistance. Robert W. Kuhn received his diploma engineer degree (Dipl.-Ing.) in geodesy at the Technical University of Berlin, Germany, in 2000. His current work on a PhD thesis focuses on calibration and image processing. Jens Kaszubiak was born in Blankenburg, Germany, in 1977. He received his diploma engineer degree (Dipl.-Ing.) in electrical engineering at the University of Magdeburg, Germany, in 2002. His current research work focuses on vision-based driver assistance and hardware-software codesign. Bernd Michaelis was born in Magdeburg, Germany, in 1947. He received a Masters Degree in Electronic Engineering from the Technische Hochschule, Magdeburg, in 1971 and his first PhD in 1974. Between 1974 and 1980 he worked at the Technische Hochschule, Magdeburg, and was granted a second doctoral degree in 1980. In 1993 he became Professor of Technical Computer Science at the Otto-von-Guericke University, Magdeburg. His research work concentrates on the field of image processing, artificial neural networks, pattern recognition, processor architectures, and microcomputers. Professor Michaelis is the author of more than 150 papers. Gerald Krell was born in Magdeburg, Germany, in 1964. He earned his diploma in electrical engineering in 1990 and his doctorate in 1995 at Otto-von-Guericke University of Magdeburg. Since then he has been a research assistant. His primary research interest is focused on digital image processing and compression, electronic hardware development, and artificial neural networks.     

基于微型传感器驱动的三维实时运动人体模型

建立一种运用于人体运动捕获与再现系统的人体模型,实现人体运动实时控制模型的运动.根据微型传感器人体运动捕获与再现系统的特点,提出一种三维人体模型的层次化结构建模方法和多边形分组皮肤变形方法.该方法以生物动力学为基础,根据人体关节的运动特征进行分层表示,采用传感器数据驱动并控制人体骨架模型的运动以及皮肤模型的变形,实时再现真实人体运动.实验表明,新建模方法适用于传感器数据驱动人体模型的实时运动再现,并能够逼真地体现人体运动的生物力学特征.     

Dense 3D face alignment from 2D video for real-time use

To enable real-time, person-independent 3D registration from 2D video, we developed a 3D cascade regression approach in which facial landmarks remain invariant across pose over a range of approximately 60°. From a single 2D image of a person's face, a dense 3D shape is registered in real time for each frame. The algorithm utilizes a fast cascade regression framework trained on high-resolution 3D face-scans of posed and spontaneous emotion expression. The algorithm first estimates the location of a dense set of landmarks and their visibility, then reconstructs face shapes by fitting a part-based 3D model. Because no assumptions are required about illumination or surface properties, the method can be applied to a wide range of imaging conditions that include 2D video and uncalibrated multi-view video. The method has been validated in a battery of experiments that evaluate its precision of 3D reconstruction, extension to multi-view reconstruction, temporal integration for videos and 3D head-pose estimation. Experimental findings strongly support the validity of real-time, 3D registration and reconstruction from 2D video. The software is available online at http://zface.org.