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三维可视化技术在医学领域中的应用 总被引:2,自引:1,他引:1
在医学软件的开发过程中,实现三维重建技术的优劣是系统设计的难点和重点.在探讨面绘制与体绘制技术的基础上,使用OpenGL及VTK工具包完成可视化具体操作,并对其结果进行简要分析.利用患者髋关节CT数据,实施了基于OpenGL的Marching Cube算法、三维纹理映射算法,以及基于VTK的Marching Cube、Ray Casting算法,并对实现过程及实现效果进行了对比分析.基于OpenGL与基于VTK的面绘制技术及体绘制技术均能较好呈现患者髋关节的三维解剖结构信息.其中,面绘制可有效地绘制出三维体的表面,但缺乏内部信息的表达;体绘制真实感较好,但渲染速度较慢,不适合用于实时系统的表达.VTK可视化方法实现简单,适用于快速显示数据空间信息,但其三维交互功能不足;OpenGL属于底层API,可灵活完成各项交互操作及渲染任务,但其编码较为复杂. 相似文献
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提出一种抛物线插值的体绘制分段积分方法,并改进了基于剪切几何纹理化的体数据剖切绘制.首先将采样段内的颜色值用抛物线插值近似代替,计算各采样段的光强值,代替采样点用于体绘制积分方程,即使低采样率下仍能获得较好的图像质量.对体数据进行剖切绘制时,与传递函数相结合,根据剪切几何形状和位置修改体数据中的相应体素值,使之对最终绘制图像不作贡献,达到剪切绘制的目的,并实现了基于剪切几何和基于体数据阈值分割的剖切算法.试验结果表明,本文方法明显提高了绘制图像的质量,降低了剖切绘制时的内存使用,同时提高了剖切绘制的速度. 相似文献
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针对多媒体无线通信的特点,提出了一种结合自适应纠错技术与联合优化技术的新策略,充分考虑了联合编码的自适应纠错特性和联合优化特性,分析了优化的信源编码算法和优化的信道编码算法.实验仿真结果表明,该方法能够使图像数据在高码率下达到较好的抗噪性能. 相似文献
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用于纯方位跟踪的简化粒子滤波算法及其硬件实现 总被引:2,自引:2,他引:0
针对粒子滤波运算量大,硬件复杂性高的问题,该文提出了一种用于纯方位跟踪的简化粒子滤波算法,该算法引入了一种新的基于阈值的重采样方法,降低了硬件实现的复杂度.在算法研究的基础上,论文研究了基于FGPA的硬件电路实现方法,给出了系统的整体硬件结构及重采样/采样模块的实现方案,讨论了粒子滤波硬件实现的资源优化及时间优化问题.仿真结果表明,对于纯方位跟踪问题,该粒子滤波算法具有优于扩展Kalman滤波器(EKF)的性能;硬件电路实验表明,该滤波器可以实现对被动目标的纯方位跟踪,并具有比通用粒子滤波器较快的处理速度. 相似文献
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Direct isosurface volume rendering is the most prominent modern method for medical data visualization. It is based on finding intersection points between the rays corresponding to pixels on the screen and isosurface. This article describes a two-pass algorithm for accelerating the method on the graphic processing unit (GPU). On the first pass, the intersections with the isosurface are found only for a small number of rays, which is done by rendering into a lower-resolution texture. On the second pass, the obtained information is used to efficiently calculate the intersection points of all the other. The number of rays to use during the first pass is determined by using an adaptive algorithm, which runs on the central processing unit (CPU) in parallel with the second pass of the rendering. The proposed approach allows to significantly speed up isosurface visualization without quality loss. Experiments show acceleration up to 10 times in comparison with a common ray casting method implemented on GPU. To the authors’ knowledge, this is the fastest approach for ray casting which does not require any preprocessing and could be run on common GPUs. 相似文献
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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。 相似文献
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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%。 相似文献
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We present a novel GPU‐based ray‐casting algorithm for volume rendering of unstructured grid data. Our volume rendering system uses a ray‐casting method that guarantees accurate rendering results. We also employ the per‐pixel intersection list concept in the Bunyk algorithm to guarantee an accurate result for non‐convex meshes. For efficient memory access for the lists on the GPU, we represent the intersection lists for all faces as an array with our novel construction algorithm. With the intersection lists, we perform ray‐casting on a GPU, and a GPU thread handles each ray. To increase ray‐coherency in a thread block and improve memory access efficiency, we extend a prior image‐tile‐based work distribution method to fit modern GPU architectures. We also show that a prior approach using a per‐thread local buffer to reduce redundant computation is not appropriate for modern GPU architectures. Instead, we take an on‐demand calculation strategy that achieves better performance even though it allows duplicate computations. We applied our method to three unstructured grid datasets with different characteristics. With a GPU, our method achieved up to 36.5 times higher performance for the ray‐casting process and 19.7 times higher performance for the whole volume rendering process compared with the Bunyk algorithm using a CPU core. Also, our approach showed up to 8.2 times higher performance than a GPU‐based cell projection method while generating more accurate rendering results. These results demonstrate the efficiency and accuracy of our method. 相似文献
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Alexandre S. Nery Nadia Nedjah Felipe M. G. França 《Analog Integrated Circuits and Signal Processing》2012,70(2):189-202
Real time rendering of three-dimensional scenes in high photorealistic details is a hard task, such as in the ray tracing
rendering algorithm. In general, the performance achieved by a sequential software-based implementation of ray tracing is
far from satisfactory. However, parallel implementations of ray tracing have been enabling reasonable real time performance,
as the algorithm is embarrassingly parallel. Thus, a custom parallel design in hardware is likely to achieve an even higher
performance. In this paper, we propose a hardware parallel architecture capable of dealing with the main desirable features
of ray tracing, such as shadows and reflection effects, imposing low area cost and a promising rendering performance. Such
architecture, called GridRT, is based on the Uniform Grid acceleration structure and is intended to deliver massive parallelism
through parallel ray-triangle intersection tests as well as parallel processing of many rays. A hardware implementation of
the proposed architecture is presented, together with some performance results and resources requirements. The rendering is
reduced by 80% using a grid configuration of eight processing elements. 相似文献
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针对在基于DWT-DCT进行数字音频水印嵌入,在已嵌入水印的音频受到噪声干扰、低通滤波、重采样等常见的攻击时,其鲁棒性差以及安全性弱的情况.提出了一种新的的盲水印嵌入算法.该算法对原始音频信号完成分帧预处理后,对每帧信号应用离散小波变换(DWT),选取三级低频分量进行离散余弦变换(DCT),先把得到的一维信号平均分解为两个片段,然后进行奇异值分解(SVD),根据奇异值的特性将水印信息嵌入到奇异矩阵.在水印图像的预处理上,采用了以Arnold变换为基础,将水印图像降维,方便水印信息的嵌入.并且通过添加密匙来提升数字音频水印的安全性.使用5个不同种类的音乐类型,进行仿真实验.实验结果表明:其误码率(BER)在0.0896以下,相关系数(NC)在0.9708以上.本算法对噪声干扰、低通滤波、重采样、重量化、剪切、压缩等常见的攻击方法具有良好的鲁棒性. 相似文献
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虚拟场景的绘制算法是计算机可视化的重要内容,传统的基于几何模型的绘制和基于图像的绘制不能很好地满足需求,因此考虑以不同模型为基元的绘制算法.详细介绍了点绘制方法、面绘制方法和体绘制方法,使用双目相机获取深度图像,并选用了代表性的算法进行实验,点绘制算法中质量和速率兼顾的自适应绘制算法,面绘制中简单易实现的MC算法,体绘... 相似文献
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Cattleya Duanggate Bunyarit Uyyanonvara Stanislav S. Makhanov Sarah Barman Tom Williamson 《Journal of Visual Communication and Image Representation》2011,22(4):345-352
This paper proposes a novel segmentation method based on the scale space techniques endowed with a feature stability approach. The novelty of the paper is the lifetime of the space-scale blobs measured not only by their presence and disappearance but by the stability of the features characterizing the objects of interest as well. Our numerical experiments show that the algorithm outperforms the conventional space scale algorithm applied to variable size and variable shape objects. The proposed algorithm can be used as a preprocessing step in object or pattern recognition applications to produce seeds for more accurate image segmentation methods such as the snakes or the level set techniques. 相似文献
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针对粒子滤波算法中粒子退化问题,提出一种基于粒子分组优化的自适应跟踪算法。在传统粒子滤波算法的基础上,分别从特征直方图的建立和粒子重采样策略两个角度进行改进。综合考虑目标与背景的特征显著性和相似性两个因素建立比值关系进行量化分析,选取能够最大程度区分前景目标和背景的特征,并以此区分度作为权值确定直方图中所选特征的区间数。通过实时分析粒子间相对空间分布位置,建立一种新的粒子重采样策略,采用复制、线性组合、淘汰等不同形式对粒子的数量和分布位置进行自适应调整,使得粒子性能得到优化。实验仿真结果验证了所提算法的有效性。 相似文献