基于PC的体绘制技术

研究一种基于PC的体绘制技术,采用改进的光线投射算法,并以Visual C 6.0为开发环境,实现基于Open-GL光照模型的直接体绘制系统,突破现有三维体绘制大都基于专用图像工作站的现状,在微机上成功地实现从建立灰度体素模型、灰度体数据显示,包括灰度梯度计算、光照效应计算、投影合成显示等整个体绘制过程。并在Widows 2000平台下形成界面友好的人机交互通用化系统,从而较好地解决了体绘制生成图像质量和显示速度之间的深刻矛盾,达到快速有效完成三维图像显示的目的,并应用于外科手术支援系统中。     

复杂电磁环境三维态势展示方法研究

在复杂电磁空间斗争这条无形的战线上,对电磁环境的准确、直观描述一直是制约指挥人员实施准确、高效指挥的关键因素,本文围绕复杂电磁环境三维可视化方法展开研究。首先提出了混合八叉树分割方法解决了传统八叉树不能对大规模体数据直接体绘制的问题,设计了球形规则网格体数据组织模型,通过抽象电磁环境数据模型的输入、输出和计算功能,构建了复杂电磁环境的通用组织计算框架。针对传统光线投射直接体绘制算法不能正确处理视锥体裁剪问题,提出了一种视锥体裁减修正的方法,通过绘制视锥体近、远截面与体数据包围盒的相交面,解决了由于被视锥体裁剪而丢失数据的绘制错误问题。研究运用等值线绘制算法、颜色映射切片绘制算法和光线投射算法三者相结合的可视化方法,从不同高度和不同方向切割电磁环境,不仅能直观感受到复杂电磁环境的全貌,而且能观察对作战指挥最有影响的细节信息。     

用于体绘制可视化的交互式直方图传递函数设计研究

医学图像体绘制可视化可以直接显示体数据的内部信息,成为可视化研究的一个重要的领域。由于医学图像数据本身的复杂性和传递函数的设计的灵活性,可视化传递函数成为研究的热点。通过CT,MRI设备获取的体数据,其质量受噪声影响严重,首先使用非线性增强方法对数据进行预处理,之后对体数据进行边界体素预判,并构造二维直方图用以设计传递函数,最终用光线投射算法绘制体数据。利用文中方法对大小为256×256×161的牙齿数据集进行非线性增强去噪,并设计传递函数,牙齿数据噪声得到了有效地抑制,不同边界区分比较明显。此外对牙齿体数据进行边界体素预判后,通过二维直方图查找边界的时间由78.2s减少至28.3s。实验结果表明,文中方法能有效地去除噪声、查找边界并提高绘制速度。基于构造出的直方图能够方便进行半自动化传递函数设计,提高绘制结果的质量。     

基于改进光线投射算法的室内烟雾可视化研究

针对传统光线投射算法在三维场景中绘制大量烟雾数据时存在计算资源消耗大、绘制速度缓慢等一系列问题,提出一种基于改进光线投射算法的室内烟雾可视化方法。将三维数据场按照统一大小划分成均匀的数据块,求出光线穿越数据块时入射点和出射点的中点位置,利用视点和中点之间的距离比例来调整采样频率,从而获得重采样点的位置。再通过对光线上的重采样点进行分级分组操作,对处于不同级别的采样点采取不同的插值策略,最后使用图像合成算法完成光线上重采样点数据值的映射,得到室内烟雾的渲染效果。实验结果表明,该方法是可行且有效的,与现有的光线投射算法相比,在保证绘制图像真实性和稳定性的前提下,改进过后的光线投射算法极大地减少了渲染过程中重采样和线性插值时的计算量,同时帧率能够稳定保持在75frame·s^-1左右,可满足不同室内场景下烟雾的实时绘制要求。     

基于二维最大熵阈值分割的体绘制技术研究

针对光线投射体绘制算法存在的运算量大,绘制速度慢的问题,提出了光线投射体绘制过程中对工业CT断层图像原始数据场进行二维最大熵阈值分割预处理的改进,利用二维直方图熵最大化确定阈值的范围,寻找参数的最优组合,结合阈值面积消除法滤除一些噪声将图像二值化,减少重建体数据量,加速光线投射的效率.取得了较好的显示效果.     

模糊表面构造,阻光度映射及快速体绘制研究

直接体绘制技术利用半透明效果能够在一定程度上绘制三维数据的精细结构但是,由于数据场中的所有体素都参与图像的生成过程,绘制时间较长,基于表面的方法在图像分割不儿表面拓扑结构非常复杂时表达能力往往有限,本文提出一种综合上术寅途中 思想的基于模糊表面的体绘制方法,首先我们选择合适的阻江度映射方案增强边界对最科成像的贡献,其次,只是模糊边界内的绘制过程,并以层代替体素为基本处理单元,减少了成像时间,我们应     

VTK技术在雷达图像可视化中的研究与应用

利用VTK对雷达图像数据进行三维可视化研究,其中研究了表面绘制和体绘制两种绘制技术：表面绘刺用移动立方体法实现,体绘制用合成光线投影算法实现。实验高效快捷地显示了雷达二维图像,实现了雷迭四波数据的空间整体三维重建显示和x,y,z三维任意切面的雷达回波强度显示,并且可以任意方向切割、旋转、放大与平移三维图像。VTK应用于雷达图像三维可视化更为直观和全面的展现了空间回波的分布状况。     

基于GPU加速的改进的光线投射算法研究

传统的医学图像体绘制算法大多通过CPU端实现,为解决传统算法存在绘制时间较长,交互不够流畅,且使用平台单一等问题,提出了一种基于图形处理器(GPU)的医学序列影像的实时体绘制技术。通过对不透明度值设置阈值,提前终止光线计算,并在光线遍历体数据时,调整采样间距,改进了光线投射算法。实验结果表明,对其中一组最大数据(931张切片)的绘制时间为1.3 s左右,交互时的绘制帧数在20~40之间。在绘制时间方面,不仅比传统的基于CPU的算法有大幅度提高,相比于前人的基于GPU的算法也有明显改进,加速比可以达到1.5左右。     

视点相关光线投射算法在三维云可视化方面的应用

针对绘制海量云数据时传统光线投射算法计算量大、绘制缓慢等问题,提出了一种基于视点相关光线投射算法的三维云可视化方法。该方法首先采用基于多分辨率方法的数据预处理策略,然后采用基于视点相关系数的自适应采样频率计算方法确定重采样点的位置,并利用三阶段插值算法计算重采样点的值,最后采用基于块重要性加权香农熵的二维传输函数完成颜色值和不透明度的映射关系,从而实现图像的合成。实验结果表明,该方法计算复杂度低、执行效率高,与现有的光线投射算法相比,不仅图像的重构质量得到了提高,绘制时间也减少了约30%。     

三维地震数据的可视化

传统的地震数据解释方法是利用地震剖面与水平切片的二维图象显示三维数据,它具有很大的局限性。科学可视化技术的出现使得三维数据三维解释成为可能。将科学可视化技术应用于三维地震数据场,则产生了三维地震数据可视化技术,它主要包括面可视化与直接体绘制两种技术。本文主要研究三维地震数据场的直接体绘制方法——光线投射算法。     

Hole‐Filling Methods Using Depth and Color Information for Generating Multiview Images

This paper presents new hole‐filling methods for generating multiview images by using depth image based rendering (DIBR). Holes appear in a depth image captured from 3D sensors and in the multiview images rendered by DIBR. The holes are often found around the background regions of the images because the background is prone to occlusions by the foreground objects. Background‐oriented priority and gradient‐oriented priority are also introduced to find the order of hole‐filling after the DIBR process. In addition, to obtain a sample to fill the hole region, we propose the fusing of depth and color information to obtain a weighted sum of two patches for the depth (or rendered depth) images and a new distance measure to find the best‐matched patch for the rendered color images. The conventional method produces jagged edges and a blurry phenomenon in the final results, whereas the proposed method can minimize them, which is quite important for high fidelity in stereo imaging. The experimental results show that, by reducing these errors, the proposed methods can significantly improve the hole‐filling quality in the multiview images generated.     

基于Kinect的实时深度提取与多视绘制算法

提出了一种基于Kinect的实时深度提取算法和单纹理+深度的多视绘制方法。在采集端,使用Kinect提取场景纹理和深度,并针对Kinect输出深度图的空洞提出一种快速修复算法。在显示端,针对单纹理+深度的基于深度图像的绘制(DIBR,depth image based rendering)绘制产生的大空洞,采用一种基于背景估计和前景分割的绘制方法。实验结果表明,本文方法可实时提取质量良好的深度图,并有效修复了DIBR绘制过程中产生的大空洞,得到质量较好的多路虚拟视点图像。以所提出的深度获取和绘制算法为核心,实现了一种基于深度的立体视频系统,最终的虚拟视点交织立体显示的立体效果良好,进一步验证了本文算法的有效性。本文系统可用于实景的多视点立体视频录制与播放。     

Depth video spatial and temporal correlation enhancement algorithm based on just noticeable rendering distortion model

Spatial and temporal inconsistency of depth video deteriorates encoding efficiency in three dimensional video systems. A depth video processing algorithm based on human perception is presented. Firstly, a just noticeable rendering distortion (JNRD) model is formulated by combining the analyses of the influence of depth distortion on virtual view rendering with human visual perception characteristics. Then, depth video is processed based on the JNRD model from two aspects, spatial and temporal correlation enhancement. During the process of spatial correlation enhancement, depth video is segmented into edge, foreground, and background regions, and smoothened by Gaussian and mean filters. The operations of the temporal correlation enhancement include temporal–spatial transpose (TST), temporal smoothing filter and inverse TST. Finally, encoding and virtual view rendering experiments are conducted to evaluate the proposed algorithm. Experimental results show that the proposed algorithm can greatly reduce the bit rate while it maintains the quality of virtual view.     

New techniques for efficient sliding thin-slab volume visualization

High-resolution three-dimensional (3-D) volumetric images obtained by today's radiologic imaging scanners are rich in detailed diagnostic information. Despite the many visualization techniques available to assess such images, there remains information that is challenging to uncover, such as the location of small structures (e.g., mediastinal lymph nodes, narrowed-airway regions). Recently, sliding thin-slab (STS) visualization was proposed to improve the visualization of interior structures. These STS techniques sometimes depend on user opacity specifications or extra preprocessing, and other rendering approaches that use the general STS mechanism are conceivable. We introduce two techniques for STS volume visualization. The first, a depth (perspective) rendering process, produces an unobstructed, high-contrast 3-D view of the information within a thin volume of image data. Results are a function of relative planar locations. Thus, rendered views accurately depict the internal properties that were initially captured as position and intensity. The second method produces a gradient-like view of the intensity changes in a thin volume. Results can effectively detect the occurrence and location of dramatic tissue variations, often not visually recognized otherwise. Both STS techniques exploit the concept of temporal coherence to form sequences of consecutive slabs, using information from previously computed slabs. This permits efficient real-time computation on a general-purpose computer. Further, these techniques require no preprocessing, and results are not dependent on user knowledge. Results using 3-D computed tomography chest images show the computational efficiency and visual efficacy of the new STS techniques.     

Morphological Filters and Wavelet-based Histogram Equalization Image Enhancement for Weak Target Detection

1　IntroductionInrecentdecades ,infrared (IR)andvisualimagesensorshavebeenusedinmanyapplications .Thesensorper formancedependsonitsworkcondition .Insomecasesthesensorperformancewoulddegenerateandimagequalitydescend ,makingtheweakincontrastandgray levelsda…     

A direct multi-volume rendering method aiming at comparisons of 3-Dimages and models

The authors present a new method for direct volume rendering of multiple three-dimensional (3-D) functions using a density emitter model. The work is aimed at obtaining visual assessment of the results of a 3-D image registration algorithm which operates on anisotropic and non-segmented medical data. They first discuss the fundamentals associated with direct, simultaneous rendering of such datasets. Then, they recall the fuzzy classification and fuzzy surface rendering theory within the density emitter model terminology, and propose an extension of standard direct volume rendering that can handle the rendering of two or more 3-D functions; this consists of the definition of merging rules that are applied on emitter clouds. The included rendering applications are related on one hand, to volume-to-volume registration, and on the other hand, to surface-to-volume registration: the first case is concerned with global elastic registration of CT data, and the second one presents fitting of an implicit surface over a CT data subset. In these two medical imaging application cases, the rendering scheme offers a comprehensive appreciation of the relative position of structural information     

基于图像边缘特征的深度上采样算法

针对低分辨率深度图像上采样容易导致边缘模糊问 题,提出了一种基 于图像边缘特征的深度上采样算法。一方面,利用相同低分辨率深度和彩色图像的相关性系 数,自适应调 节深度图像边缘上采样过程中深度和彩色的权重;另一方面,结合上采样值和低分辨率深度 图像中邻近像 素值,对低分辨率深度图像的不连续区域进行求精操作以进一步减少边缘模糊现象。实验结 果表明,本文算法 的性能优于近年文献中提出的算法。本算法上采样深度图像的平均坏点率(B PR)为2.07%,均方根误差(RMSE )为3.46,峰值信噪比(PSNR)为38.58dB,绘制 虚拟视点的平均PSNR为39.58dB。