Lagrangian-Eulerian advection of noise and dye textures for unsteady flow visualization

A new hybrid scheme, called Lagrangian-Eulerian advection (LEA), that combines the advantages of the Eulerian and Lagrangian frameworks is applied to the visualization of dense representations of time-dependent vector fields. The algorithm encodes the particles into a texture that is then advected. By treating every particle equally, we can handle texture advection and dye advection within a single framework. High temporal and spatial correlation is achieved through the blending of successive frames. A combination of particle and dye advection enables the simultaneous visualization of streamlines, particle paths and streak-lines. We demonstrate various experimental techniques on several physical flow fields. The simplicity of both the resulting data structures and the implementation suggest that LEA could become a useful component of any scientific visualization toolkit concerned with the display of unsteady flows.     

实时的2D不稳定流场可视化算法

为了提高不稳定流场可视化结果的绘制质量和绘制速度,提出一种基于平流技术与纹理混合的不稳定流场可视化改进算法。算法分别通过图像平流来获得流场动画的时间一致性,通过质点平流来获得流场动画单帧图像的空间一致性,最后通过纹理混合使流场动画的时间、空间一致性统一起来。通过这种方式获得的流场动画纹理细节清晰、帧间过渡平滑,绘制速度较快,具有较高的时间、空间一致性,可以准确地反映不稳定流场的动态变化。     

Multidimensional illumination functions for visualization of complex 3D environments

This paper presents a new view-independent, energy equilibrium method for determining the light distributed in a complex 3D environment consisting of surfaces with general reflectance properties. The method does not depend on discretization of directions or discretization of surfaces to differential elements. Hence, it is a significant improvement over the earlier complete view-independent method which is computationally intractable for complex environments or the hybrid methods which include an extended view-dependent ray tracing second pass. The new method is based on an efficient data structure of order O(N²) called the spherical cover. The spherical cover elegantly captures the complex multidimensional directional nature of light distributed over surfaces. Subdivision techniques based on range estimation of various parameters using interval-arithmetic-like methods are next described for efficiently computing the spherical cover for a given 3D environment. Using the spherical cover, light is progressively propagated through the environment until energy equilibrium is reached. Complexity analysis of the propagation step is carried out to show that the method is computationally tractable. The paper also includes a comprehensive review of earlier rendering techniques viewed from the point of view of capturing the multidimensional nature of light distribution over surfaces.     

Interactive visualization of 3D seismic data: a volumetric method

The authors demonstrate the utility of examining seismic data with a volumetric scheme, whereby a synoptic view of the interior of the data volume is possible before conventional interpretation. High-amplitude seismic events, representing reflections from subterranean surfaces, are transformed to color pixels, and the resulting 3-D images reveal the structure of the geological layers. Such morphological features as hills, valleys, and faults are apparent indicating that the approach could prove useful for identifying potential oil reservoirs. The authors implement the technique on a personal computer to produce displays of similar quality, but they find that the construction of the 3-D images is too slow for reasonable interactivity. However, with the addition of a parallel-processing accelerator, a personal-computer-based workstation would be feasible for this kind of 3-D visualization and interpretation     

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。     

基于纹理的三维超声实时体绘制

三维纹理的体绘制算法由于其利用显卡加速渲染、硬件实现三线性插值和不丢失图像的纹理特性3大优点，尤其适合医学超声数据的实时三维可视化。显示大量多边形切片（slice polygon）是当前影响三维纹理体绘制渲染实时性的重要因素。为了克服常用的参数化算法在快速生成大量多边形切片时性能不佳的缺点，提出了的空间活动边表的方法，充分利用各个多边形切片之间的空间相关性实现增量计算，明显提高了计算速度。     

3D flow features visualization via fuzzy clustering

A key approach to visualizing a flow field is to emphasize regions with significant behavior. However, it is difficult to give concrete criteria for classifying feature regions. In this paper, we use a novel framework in which fuzzy sets are used to determine flow features: Fuzzy relationships assess structural properties of features. A fuzzy c-means-like clustering algorithm is used to evaluate the importance of each voxel. Our approach can be readily modified with new fuzzy relationships describing other features of interest to users. We use a multi-resolution approach which displays structural features in greater detail, and represents the background by coarse-grained information. Experiments on synthetic and real datasets show that our framework can highlight significant aspects of the whole flow while avoiding occlusion and clutter. Interactive performance is achieved via a GPU implementation.     

基于Web的三维实时井眼轨迹可视化方法研究与实现

针对基于Web的实时三维可视化应用需求,结合邻近井段的结构形状、变化规律,改进了贝塞尔曲线拟合算法,提高了测斜数据处理速率和曲化度,并采用Away3D技术实现轨迹的三维展示。应用结果表明,轨迹绘制细腻流畅,系统具备良好的实时性。     

Flow radar glyphs--static visualization of unsteady flow with uncertainty

A new type of glyph is introduced to visualize unsteady flow with static images, allowing easier analysis of time-dependent phenomena compared to animated visualization. Adopting the visual metaphor of radar displays, this glyph represents flow directions by angles and time by radius in spherical coordinates. Dense seeding of flow radar glyphs on the flow domain naturally lends itself to multi-scale visualization: zoomed-out views show aggregated overviews, zooming-in enables detailed analysis of spatial and temporal characteristics. Uncertainty visualization is supported by extending the glyph to display possible ranges of flow directions. The paper focuses on 2D flow, but includes a discussion of 3D flow as well. Examples from CFD and the field of stochastic hydrogeology show that it is easy to discriminate regions of different spatiotemporal flow behavior and regions of different uncertainty variations in space and time. The examples also demonstrate that parameter studies can be analyzed because the glyph design facilitates comparative visualization. Finally, different variants of interactive GPU-accelerated implementations are discussed.     

RETRACTED ARTICLE: Texture-guided volumetric deformation and visualization using 3D moving least squares

Examining and manipulating the large volumetric data attract great interest for various applications. For such purpose, we first extend the 2D moving least squares (MLS) technique into 3D, and propose a texture-guided deformation technique for creating visualization styles through interactive manipulations of volumetric models using 3D MLS. Our framework includes focus+context (F+C) visualization for simultaneously showing the entire model after magnification, and the cut-away or illustrative visualization for providing a better understanding of anatomical and biological structures. Both visualization styles are widely applied in the graphics areas. We present a mechanism for defining features using high-dimensional texture information, and design an interface for visualizing, selecting and extracting features/objects of interest. Methods of the interactive or automatic generation of 3D control points are proposed for the flexible and plausible deformation. We describe a GPU-based implementation to achieve real-time performance of the deformation techniques and the manipulation operators. Different from physical deformation models, our framework is goal-oriented and user-guided. We demonstrate the robustness and efficiency of our framework using various volumetric datasets.     

Lightweighting for Web3D visualization of large-scale BIM scenes in real-time

As a result of informatization in construction, Building Information Modeling (BIM) has now become a core technology for smart construction. We present a Web3D-based lightweighting solution for real-time visualization of large-scale BIM scenes, considering the redundancy, semantics, and the parameterization of BIM data under the limited resources of network bandwidth and web browsers. Taking the Industry Foundation Classes (IFC) as the input data format, we firstly conduct a semantics-guided lightweighting operation on the raw BIM scenes by removing the repetitive objects and parameterizing the swept surfaces. Secondly, we extract the exterior products from the raw BIM buildings for visibility culling and construct a Double-Layered Sparse Voxel (DLSV) index based on sparse voxelization. Thirdly, we integrate the above two together into a new data structure named Incremental Frustum of Interest (I-FOI) to manage the scene data in real-time. Our experiments demonstrate that: (1) with the semantics information, our method is able to significantly reduce the redundancy of raw large-scale BIM scenes; (2) the DLSV structure supports progressive data loading and facilitates the indoor/outdoor visibility culling efficiently; and (3) the I-FOI introduces a frustum incremental-driven mechanism into progressive data loading or unloading to improve the efficiency of resource consumption.     

实时界定雷达电磁互扰区域的三维可视化方法

为了便于多方位、多角度观察和分析舰艇编队中雷达电磁互扰的区域, 利用等值面的分界特性, 通过使用能流密度和干扰余量来表现舰艇编队中雷达电磁互扰的程度, 提出使用递进式栅格采样的极值八叉树快速重构等值面的方法, 还提出使用等值面差别显示的方法建立实时交互的三维显示图和俯视、前视、侧视的动态切面图, 来动态显示舰艇编队雷达电磁互扰的仿真结果。通过对6艘舰艇共16部单脉冲雷达的仿真, 实验结果表明该方法可行、有效。该方法还可以应用到其他电磁环境的实时三维可视化中, 也可以应用在研究和预防无人机被雷达电磁干扰的三维仿真中。     

Tensor3D: A computer graphics program to simulate 3D real-time deformation and visualization of geometric bodies

Tensor3D is a geometric modeling program with the capacity to simulate and visualize in real-time the deformation, specified through a tensor matrix and applied to triangulated models representing geological bodies. 3D visualization allows the study of deformational processes that are traditionally conducted in 2D, such as simple and pure shears. Besides geometric objects that are immediately available in the program window, the program can read other models from disk, thus being able to import objects created with different open-source or proprietary programs. A strain ellipsoid and a bounding box are simultaneously shown and instantly deformed with the main object. The principal axes of strain are visualized as well to provide graphical information about the orientation of the tensor's normal components. The deformed models can also be saved, retrieved later and deformed again, in order to study different steps of progressive strain, or to make this data available to other programs. The shape of stress ellipsoids and the corresponding Mohr circles defined by any stress tensor can also be represented. The application was written using the Visualization ToolKit, a powerful scientific visualization library in the public domain. This development choice, allied to the use of the Tcl/Tk programming language, which is independent on the host computational platform, makes the program a useful tool for the study of geometric deformations directly in three dimensions in teaching as well as research activities.     

Computational visualization of unsteady flow around vehicles using high performance computing

One of the largest-scale unstructured Large Eddy Simulation (LES) of flow around a full-scale road vehicle is conducted on the Earth Simulator in Japan. The main objective of our study is to look into the validity of LES for the assessment of vehicle aerodynamics, especially in the context of its possibility for unsteady or transient aerodynamic forces. Firstly, the aerodynamic LES proposed is quantitatively validated on the ASMO simplified model by comparing the mean pressure distributions on the vehicle surface with those obtained by a conventional Reynolds-Averaged Navier-Stokes simulation (RANS) or a wind tunnel measurement. Then, the method is applied to the full-scale vehicle with complicated geometry to qualitatively investigate the capability of capturing organized flow structures around the vehicle. Finally, unsteady aerodynamic forces acting on the vehicle in transient yawing angle change are estimated and relationship between the flow structures and the transient aerodynamic forces is mentioned. As a result, it is demonstrated that LES will be a powerful tool for the vehicle aerodynamic assessment in the foreseeable future, because it can provide precious aerodynamic data which conventional wind tunnel tests or RANS simulations are difficult to provide.     

基于信息熵种子点选取的流线可视化

有效的种子点选取方法是影响流线分布洞悉流场特性的关键。在保持流场变化规律与重要特征准确描述前提下,为了解决由过多流线所导致的遮挡与杂乱问题,提出了基于贪婪策略和蒙特卡洛的两种种子点选取方法。基于贪婪策略的种子点选取方法通过流场信息熵的计算,对流场中的关键特征具有高度敏感性。基于蒙特卡洛种子点选取方法根据均匀随机分布函数生成输入,基于信息熵计算输入点影响半径确定流线分布。通过多个数据集对两种选取方法实验,结果表明基于贪婪策略选取方法可高效捕获流场的关键特征,基于蒙特卡洛方法选取流线更加均匀,保持了流场全局变化规律,两种方法的结合得到更优化的流场可视化效果。     

Importance sampling for volumetric illumination of flames

Physically based rendering of scenes with volumetric illumination of flames remains a challenging problem due to the complexity of their heterogeneous radiative properties. Current bidirectional importance sampling strategies have been focusing on emissive light sources without anisotropic extinction. In this paper, we present an efficient importance sampling method for volumetric light sources with anisotropic extinction. According to the radiative properties of flames, we separate the computation of anisotropic extinction from the evaluation of illumination inside flames and utilize cluster-based hierarchies to rapidly estimate them. To exploit the coherence of radiative voxels, we also propose a new similarity metric to aggregate voxels into clusters. For each pixel to be shaded, we use these clusters to rapidly approximate the importance function of voxels, and draw final illumination samples from clusters. Our results show that this approach substantially reduces the variance of images when rendering scenes with flames.     

Influence of georeference for saturated excess overland flow modelling using 3D volumetric soft geo-objects

Existing 2D data structures are often insufficient for analysing the dynamism of saturation excess overland flow (SEOF) within a basin. Moreover, all stream networks and soil surface structures in GIS must be preserved within appropriate projection plane fitting techniques known as georeferencing. Inclusion of 3D volumetric structure of the current soft geo-objects simulation model would offer a substantial effort towards representing 3D soft geo-objects of SEOF dynamically within a basin by visualising saturated flow and overland flow volume. This research attempts to visualise the influence of a georeference system towards the dynamism of overland flow coverage and total overland flow volume generated from the SEOF process using VSG data structure. The data structure is driven by Green-Ampt methods and the Topographic Wetness Index (TWI). VSGs are analysed by focusing on spatial object preservation techniques of the conformal-based Malaysian Rectified Skew Orthomorphic (MRSO) and the equidistant-based Cassini-Soldner projection plane under the existing geodetic Malaysian Revised Triangulation 1948 (MRT48) and the newly implemented Geocentric Datum for Malaysia (GDM2000) datum. The simulated result visualises deformation of SEOF coverage under different georeference systems via its projection planes, which delineate dissimilar computation of SEOF areas and overland flow volumes. The integration of Georeference, 3D GIS and the saturation excess mechanism provides unifying evidence towards successful landslide and flood disaster management through envisioning the streamflow generating process (mainly SEOF) in a 3D environment.