基于VTK的虚拟心脏切面交互式可视化方法

为解决传统医学影像技术方向性单一的问题,满足临床医学从不同方位从整体或切面等多角度对器官组织进行观察分析的需求,提出了心脏核磁共振成像(MRI)数据的体可视化和任意角度切面的可视化方法.基于可视化工具包VTK,在VC6.0开发环境中,运用光线投射算法设计并实现了MRI羊心脏切片数据的三维体绘制,横断、冠状、矢状位置的标准切片、切面以及任意角度、任意位置切面的绘制技术.通过简单的鼠标操作就可以实时的对切面进行移动、旋转、缩放等交互操作.实验结果表明:该方法有助于医生从多个方位观察整体器官组织和切面形态.在疾病预防、医疗诊断、手术方案制定以及术后评价中具有较大的实用价值.     

三维地震数据场的并行体绘制算法

光线投射算法是一种应用广泛的体绘制基本算法,其存在的主要问题是绘制速度较慢.为了提高光线投射算法的绘制速度,利用光线间和光线内的并行性,结合三维地震数据场的特点和文件存储特性,提出了一种基于工作站机群的三维地震数据场的并行体绘制算法.地震油气解释实际应用表明本算法能满足地震解释的要求.     

基于数据场可视化技术的石油勘探应用研究

石油勘探开发是石油工业的重要部分,直接决定了我国的石油产量,在石油勘探开发过程中,会采集到大量的数据,形成三雏数据场。本文是将三维数据场可视化技术应用到石油勘探开发过程中的地质建模和数值模拟之中,达到了较好的效果。直观、准确地再现了油藏分布以及石油开发过程中的参数的动态变化,辅助相关领域工作人员的分析、设计,具有广泛应用前景。     

医学图象三维处理算法与应用

通过表面重建和体绘制,可将医学二维图象转化为三维图象.其MC算法抽取体数据中的等值面,分割出拓扑结构不变的三角面片并将其组合得到该层面的三维图象.光线投影算法将光线穿过数据场中的体元,采样得到相关象素的颜色,形成可视图.以CT切片数据为例,采用VTK开发工具重建出切片的三维图象.     

Estimating aerodynamic resistance of rough surfaces using angular reflectance

Current wind erosion and dust emission models neglect the heterogeneous nature of surface roughness and its geometric anisotropic effect on aerodynamic resistance, and over-estimate the erodible area by assuming it is not covered by roughness elements. We address these shortfalls with a new model which estimates aerodynamic roughness length (z₀) using angular reflectance of a rough surface. The new model is proportional to the frontal area index, directional, and represents the geometric anisotropy of z₀. The model explained most of the variation in two sets of wind tunnel measurements of aerodynamic roughness lengths (z₀). Field estimates of z₀ for varying wind directions were similar to predictions made by the new model. The model was used to estimate the erodible area exposed to abrasion by saltating particles. Vertically integrated horizontal flux (F_h) was calculated using the area not covered by non-erodible hemispheres; the approach embodied in dust emission models. Under the same model conditions, F_h estimated using the new model was up to 85% smaller than that using the conventional area not covered. These F_h simulations imply that wind erosion and dust emission models without geometric anisotropic sheltering of the surface, may considerably over-estimate F_h and hence the amount of dust emission. The new model provides a straightforward method to estimate aerodynamic resistance with the potential to improve the accuracy of wind erosion and dust emission models, a measure that can be retrieved using bi-directional reflectance models from angular satellite sensors, and an alternative to notoriously unreliable field estimates of z₀ and their extrapolations across landform scales.     

石油勘探开发中的数据场可视化技术应用研究

石油勘探开发是石油工业的重要部分,在石油勘探开发过程中,会采集到大量的数据,形成三维数据场,使用这些数据的目的足为了准确地再现油藏分布以及石油勘探开发过程中的参数的动态变化。该文是将三维数据场可视化技术应用到石油勘探开发过程中的地质建模和数值模拟之中,利用可视化技术,尤其是三维数据场可视化技术,实现了从大量数据中构造出三维图像。该文在算法中使用了包围盒技术和分层存储结构来提高算法的速度,达到了较好的效果,直观地再现了石油在油气藏中的状态,指导设计人员进行井位的确定,提高石油生产的效益,辅助相关领域工作人员的分析、设计,具有广泛应用前景。     

基于CUDA的体绘制GPU加速算法

本文主要是针对传统意义上的体绘制的经典算法——投射算法,在已有的GPU加速的基础上,提出了利用CUDA实现对算法的优化和加速。具体来讲,首先需要将体数据以三维纹理的形式储存在GPU的显存中,之后利用CUDA的并行处理能力对显存中的数据进行相应的处理,主要包括：生成存储顶点灰度值和颜色的纹理数组,计算顶点梯度,实现坐标系的转换,确定有效光线,利用Phong光照模型来求得光线上各等距采样点的反射分量,最后利用累加函数求得屏幕上每一点的像素值。实验结果表明：我们利用CUDA对光线投射算法的实现比传统的GPU加速算法大大提高了速度和成像质量。     

3D visualization of tomographic volume data using the generalized voxel model

Multi-slice images obtained from computer tomography and magnetic resonance imaging represent a 3D image volume. For its visualization we use a raycasting algorithm working on a gray-scale voxel data model. This model is extended by additional attributes such as membership to an organ or a second imaging modality (generalized voxel model). It is shown that the combination of different surface-rendering algorithms together with cutting and transparent display allow a realistic visualization of the human anatomy.The investigations were supported in part by the Deutsche Forschungsgemeinschaft and the Werner Otto Foundation, Hamburg.     

基于向量融合的GPU算法

传统的光线投射算法能够得到清晰的体绘制图像，但由于其运行量巨大，导致速度慢，性能低。J．Krue ger等人提出了基于GPU的光线投射算法大幅度地提高了绘制性能，但在图像融合阶段仍未能充分利用GPU的向量运算的优势。为此，本文将图像融合阶段部分标量运算转换为向量和矩阵运算，绘制性能得到了进一步提升。     

Study on Simulation of 5-axis NC Machining Process

0moxNCprograInhanghasdevelOPedfiDmmanualtoaut0-maticstagenow.Ithasrealizedtornachiningcomplexworkpiecesimulati0n,sothatmachiningcomplexwork-piececanbeachievedefficienily.However,thetime-c0n-sdringprovingcuttingreduesthisefficience,particularlyforthenewpIDductionmod-oplernanufacturing.Com-puterintegratedmanufaturing(CIM)hasputmoreatten-tiononthegenerahonofNCprogr~ng,verificati0nofreliability,soIhatmachiningprocesssimulationhasbeenanessentialpartofCAD/CAMandCIM.GeneraIly,NCprogrameango…