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1.
基于空间跳跃的三维纹理硬件体绘制算法   总被引:12,自引:0,他引:12  
童欣  唐泽圣 《计算机学报》1998,21(9):807-812
本文提出了一种用于加速三维纹理硬件体绘制的空间跳跃算法。  相似文献
2.
We study the recognition of surfaces made from different materials such as concrete, rug, marble, or leather on the basis of their textural appearance. Such natural textures arise from spatial variation of two surface attributes: (1) reflectance and (2) surface normal. In this paper, we provide a unified model to address both these aspects of natural texture. The main idea is to construct a vocabulary of prototype tiny surface patches with associated local geometric and photometric properties. We call these 3D textons. Examples might be ridges, grooves, spots or stripes or combinations thereof. Associated with each texton is an appearance vector, which characterizes the local irradiance distribution, represented as a set of linear Gaussian derivative filter outputs, under different lighting and viewing conditions.Given a large collection of images of different materials, a clustering approach is used to acquire a small (on the order of 100) 3D texton vocabulary. Given a few (1 to 4) images of any material, it can be characterized using these textons. We demonstrate the application of this representation for recognition of the material viewed under novel lighting and viewing conditions. We also illustrate how the 3D texton model can be used to predict the appearance of materials under novel conditions.  相似文献
3.
四种体绘制算法的分析与评价   总被引:7,自引:0,他引:7  
体绘制技术是科学计算可视化的重要组成部分,具有较大的研究价值和广阔的应用前景。体绘制有两种方法即间接体绘制和直接体绘制,直接体绘制(简称体绘制)以其在体数据处理及特征信息表现方面的优势,已经得到了研究者越来越多的重视。文章对四种典型的体绘制算法进行了描述,并概述了它们的改进之处,同时对它们各自的性能进行了分析和评价。  相似文献
4.
A Statistical Approach to Texture Classification from Single Images   总被引:7,自引:0,他引:7  
We investigate texture classification from single images obtained under unknown viewpoint and illumination. A statistical approach is developed where textures are modelled by the joint probability distribution of filter responses. This distribution is represented by the frequency histogram of filter response cluster centres (textons). Recognition proceeds from single, uncalibrated images and the novelty here is that rotationally invariant filters are used and the filter response space is low dimensional.Classification performance is compared with the filter banks and methods of Leung and Malik [IJCV, 2001], Schmid [CVPR, 2001] and Cula and Dana [IJCV, 2004] and it is demonstrated that superior performance is achieved here. Classification results are presented for all 61 materials in the Columbia-Utrecht texture database.We also discuss the effects of various parameters on our classification algorithm—such as the choice of filter bank and rotational invariance, the size of the texton dictionary as well as the number of training images used. Finally, we present a method of reliably measuring relative orientation co-occurrence statistics in a rotationally invariant manner, and discuss whether incorporating such information can enhance the classifiers performance.  相似文献
5.
使用GPU编程的光线投射体绘制算法   总被引:5,自引:0,他引:5  
将传统的光线投射体绘制算法在具有可编程管线的图形处理器(GPU)上重新实现.首先将体数据作为三维纹理保存在显存中,然后通过编写顶点程序和片段程序将光线进入点/离开点计算和光线遍历的计算移入GPU中执行,最后根据不同的采样点颜色混合公式实现不同的绘制效果.文中算法仅需绘制一个四边形即可完成三维重建.实验结果表明:在进行光照效果的重建时,该算法能够达到实时交互的绘制要求,并能实现半透明等复杂绘制效果.  相似文献
6.
An octree-based multiresolution hybrid framework   总被引:4,自引:0,他引:4  
The Hybrid Octree (HO) is a new approach to deal with hybrid scenes, (i.e. scenes composed of surface and volume data). The HO codes into a single model a compressed approximation of an isosurface extracted from a volume dataset and a compressed representation of the scalar data. The HO definition and its construction algorithm are provided in the paper. We also describe the capabilities of the HO to efficiently manipulate surface and volume data independently and its facilities to composite and visualize surface and volume data using texture hardware. Special emphasis is given to the HO facilities to support multiresolution. Some examples are presented and the goodness of the model is discussed.  相似文献
7.
Multiresolution volume visualization with a texture-based octree   总被引:4,自引:0,他引:4  
Although 3D texture-based volume rendering guarantees image quality almost interactively, it is difficult to maintain an interactive rate when the technique has to be exploited on large datasets. In this paper, we propose a new texture memory representation and a management policy that substitute the classical one-texel per voxel approach for a hierarchical approach. The hierarchical approach benefits nearly homogeneous regions and regions of lower interest. The proposed algorithm is based on a simple traversal of the octree representation of the volume data. Driven by a user-defined image quality, defined as a combination of data homogeneity and importance, a set of octree nodes (the cut) is selected to be rendered. The degree of accuracy applied for the representation of each one of the nodes of the cut in the texture memory is set independently according to the user-defined parameters. The variable resolution texture model obtained reduces the texture memory size and thus texture swapping, improving rendering speed.  相似文献
8.
Dynamic Textures   总被引:4,自引:0,他引:4  
Dynamic textures are sequences of images of moving scenes that exhibit certain stationarity properties in time; these include sea-waves, smoke, foliage, whirlwind etc. We present a characterization of dynamic textures that poses the problems of modeling, learning, recognizing and synthesizing dynamic textures on a firm analytical footing. We borrow tools from system identification to capture the essence of dynamic textures; we do so by learning (i.e. identifying) models that are optimal in the sense of maximum likelihood or minimum prediction error variance. For the special case of second-order stationary processes, we identify the model sub-optimally in closed-form. Once learned, a model has predictive power and can be used for extrapolating synthetic sequences to infinite length with negligible computational cost. We present experimental evidence that, within our framework, even low-dimensional models can capture very complex visual phenomena.  相似文献
9.
交互式三维医学图像可视化系统MedVis   总被引:3,自引:0,他引:3  
本文介绍了我们开发的三维医学图像可视化系统MedVis。绘制的实时性和系统的交互性是设计MedVis的两个重要原则。  相似文献
10.
彩色三维体数据场的直接体绘制方法   总被引:2,自引:0,他引:2  
提出基于光线投射和三维纹理映射的彩色体数据成像算法,研究如何从每个体素的R,G,B三元组映射成不透明度值,即不透明度转换函数。首先把原始的RGB色彩空间转换成LUV色彩空间;然后以亮度分量的中心差分来近似估计法向量,并应用Phong光照模型进行着色,根据亮度分量及其梯度等信息计算不透明度值;最后合成、累积颜色。对美国数字人男子照相彩色体数据分别采用两种算法进行实验。结果表明:基于光线投射的彩色体数据算法成像质量较高,可以表现体表毛细血管等细微结构,但速度较慢;基于三维纹理映射的彩色体数据成像算法速度较快,但成像质量适中。  相似文献
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