针对多投影仪显示墙画面校正的图像对准技术

针对多投影仪显示墙画面校正问题中相机与投影仪间图像对准问题,提出一种基于自适应细分网格的稀疏对应点加密方法,可以得到任意光滑屏幕上投影图像与相机图像间的像素级对应关系。该方法利用改进的自适应4点插值细分曲线思想构造细分网格方法,可以将投影仪图像与相机图像间稀疏对应点网格加密到任意精度,从而建立从相机到投影仪图像间的像素级一一映射关系,为多投影仪显示墙系统的几何和色彩校正提供精确的图像对准基础。与现有算法的对比分析和虚拟机场塔台仿真系统中的实际应用表明,该方法具有较高的图像对准精度,并且无显式的需求投影仪、投影屏幕和相机的内部参数。     

一种实用的多投影仪显示墙色彩校正方法

针对多投影仪显示墙系统色彩不均匀性的问题,提出一种快速、实用的独立于几何校正结果的色彩校正方法。该方法利用细分网格变形技术将现有针对平面投影屏幕的色彩校正方法推广到适应任意光滑曲面投影屏幕,同时利用加权最小二乘曲线拟合思想降低色彩测量数据量。实际进行色彩校正时,采用可编程图形处理单元(GPU)的像素着色器对投影图像的每个像素进行实时校正计算,并在实际多投影仪显示墙系统中验证了方法的有效性。     

投影也轻巧—HP sb21 投影仪试用

序去年国内的投影仪市场呈现出极好的上升势头，销量增长明显。国内共销售6万1千台投影仪，而今年则预计完成销售11至12万台。目前进军我国的国外知名投影仪厂家已超过30家。随着社会经济水平的不断提高，中小企业、培训、医疗、房地产、事业单位等机构为了工作需要将采购适合的投影仪，这将成为投影仪增长的一个潜在的巨大市场。另一个不容忽视的潜在市场则是家庭娱乐消费市场，现阶段已有不少具有较高购买能力的阶层和影像爱好者购买投影仪作为家庭影视设备。在此形势下，近日惠普一口气推出5款投影仪，其中sb21尤为引人注目。外观sb21机…     

复杂表面投影几何校正技术研究

当投影仪将图像投影到复杂表面时,为使观察者观看到不失真图像,提出了基于角点检测的几何校正方法。该方法利用对复杂表面投影白色区域图像的阈值分割来提取校正区域;进行横纵特征条纹的提取和处理,获取投影系统中特征点的坐标;通过对观察者所需的理想图像进行变换获得投影仪所需预变形图像。编写了基于OpenCV的校正软件。实验表明,该方法可以有效消除复杂表面引起的几何畸变,得到良好的观看效果。     

基于投影二维平面靶标的投影仪现场标定方法研究

投影仪的标定是结构光三维视觉测量系统应用的基础。提出了一种利用投影二维平面靶标对投影仪进行现场标定的新方法。与传统的投影仪标定相比,该方法不需要精密的标定设备,提高了标定精度,简化了标定过程,能够满足现场不断变换的要求。实验证明:该标定方法获得的结果较准确,方法简便易行,能够满足现场不断变化的测量需求。     

一个通用的投影墙软件校正系统

随着计算机图形硬件以及分布式并行图形绘制技术的不断发展，现在图形工作站以及PC集群机所能处理的图形数据量不断上升。但是，现在计算机显示设备所能提供的显示分辨率及其有限。因此，利用多台投影仪组成投影阵列进行拼接显示的投影墙技术受到越来越多的关注；此类系统的一个关键问题就是如何校正多台投影仪，使得最后拼接显示的图像没有明显的缝隙和瑕疵。该文介绍了一套通用的与具体应用无关的投影墙软件校正系统，该系统克服了传统软件校正系统在通用性、校正速度等方面的不足，取得了很好的校正效果。     

物体坐标系曲面投影立体环视图像生成算法

针对立体环视图像拼接准确度的难点,提出了一种基于物体坐标系的曲面投影图像拼接算法.根据实际应用场合建立合适的三维模型,对图像进行基于物体坐标系的纹理映射,将三维模型划分为融合、非融合区域,将原始图像映射到非融合区域,对于拼接融合区域,结合模型特点,设计了一种基于角度信息的加权平均融合算法,对拼接后的图像进行颜色校正,消...     

基于GPU投影网格的曲面渲染技术

研究曲面渲染技术对船舶、汽车、飞机造型虚拟的设计飞行器飞行实时仿真系统设计尢为重要.为了克服传统的曲面渲染方法的不足和提高实时性,充分利用图形处理器(GPU)不断提高的渲染能力,包括GPU的可编程性和高度并行计算特性,在GPU上实现了投影网格(Projected Grid)的视点相关的曲面渲染技术.从视点发出的投射光线穿过投影网格后,将根据可视化细节的重要程度,自动生成具有不同细节层次(Levels of Detail)的曲面网格,并且实时地更新网格的细节层次需求.在整个渲染过程中保持稳定的帧率,生成与视点相关的曲面光滑流畅.试验证明满足了实时交互性的要求,在工程虚拟仿真领域有广泛的应用前景.     

面向球幕投影系统的几何校正方法

摘 要：用于飞行模拟的视景仿真系统，经常会以多台投影仪同步投影以得到较大范围的 视场角。当投影机斜对屏幕或者投影屏幕为曲面时，图像会发生几何失真。针对此问题，本文 提出了一种专门面向球幕投影系统的几何校正方法，并以一个三通道显示系统为实例，详述了 该方法的理论原理以及校正流程。实例结果表明，经几何校正后，各投影图像无几何畸变，通 道过渡处几何内容完全一致。该方法是一种纯软件方法，成本小而且操作简单，能够适应于不 同的投影场景。     

曲面多通道立体投影系统及其配准方法

为解决曲面投影图像的几何失真和立体感畸变问题,设计并实现一个曲面多通道立体投影系统。该系统利用透视投影校正非线性失真,通过重投影变换对立体投影图像进行精确配准,基于NURBS曲面拟合得到投影形状的立体投影,采用图形处理单元的加速技术实现多通道间的实时边缘融合。实验结果表明,该系统具有较高的校正精度和较快的渲染速度。     

基于OpenGL的水波动画模拟

本文详细叙述了在VS2005平台下,利用OpenGL图形技术,对水表面进行模拟,提出一种改进的sin函数方法.并给出了快速实现水表面模拟的测试结果,得到了水表面模拟更加逼近的效果.     

在C#中结合OpenGL的NURBS曲面建模的实现

NURBS方法因其表示法的同一性、形状控制灵活性,在曲面造型和重构中具有重要作用。目前, 还没有在C#中开发OpenGL的标准和规范的方法。研究了在C#中利用平台调用结合OpenGL进行NURBS曲面快速建模的方法,获得了满意的结果,并在最后给出了实例。     

基于GPGPU的实体表面实时提取

为实时提取三维实体表面,提出一种基于GPGPU并行计算的实体表面实时提取方法。在分析深度剥离算法原理和GPU图形绘制管线的基础上,给出在GPU上利用深度剥离算法实现实时提取三维实体表面的算法;通过OpenGL的高级着色语言GLSL控制GPU的图形绘制管线实现了该算法,给出其伪代码。以龙、叶轮和刀具扫描体的模型为应用实例验证了该算法效果良好,特别是对于刀具扫描体表面的提取,可满足实时性要求。     

基于二次Bezier曲面的图像雕刻型面建模

针对纹理清晰且结构较简单的图像,依据其灰色或彩色像素信息,利用二次Bezier曲面直接构建雕刻型面模型。该方法通过对图像进行分割,分析和计算图像子块的像素值及位置参数,作为构建模型曲面片的特征参数,并对曲面片采用一种有限光滑拼接方法实现建模。构建的雕刻型面模型能够表述图像中原物体的基本结构特征,并能满足数字化雕刻加工的需要。算法复杂度较低,实用性强是该建模方法的特点。     

Dynamic defocus and occlusion compensation of projected imagery by model-based optimal projector selection in multi-projection environment

This paper presents a novel model-based approach of dynamic defocus and occlusion compensation method in a multi-projection environment. Conventional defocus compensation research applies appearance-based method, which needs a point spread function (PSF) calibration when either position or orientation of an object to be projected is changed, thus cannot be applied to interactive applications in which the object dynamically moves. On the other hand, we propose a model-based method in which PSF and geometric calibrations are required only once in advance, and projector’s PSF is computed online based on geometric relationship between the projector and the object without any additional calibrations. We propose to distinguish the oblique blur (loss of high-spatial-frequency components according to the incidence angle of the projection light) from the defocus blur and to introduce it to the PSF computation. For each part of the object surfaces, we select an optimal projector that preserves the largest amount of high-spatial-frequency components of the original image to realize defocus-free projection. The geometric relationship can also be used to eliminate the cast shadows of the projection images in multi-projection environment. Our method is particularly useful in the interactive systems because the movement of the object (consequently geometric relationship between each projector and the object) is usually measured by an attached tracking sensor. This paper describes details about the proposed approach and a prototype implementation. We performed two proof-of-concept experiments to show the feasibility of our approach.     

Impervious surface mapping with Quickbird imagery

This research selects two study areas with different urban developments, sizes, and spatial patterns to explore the suitable methods for mapping impervious surface distribution using Quickbird imagery. The selected methods include per-pixel based supervised classification, segmentation-based classification, and a hybrid method. A comparative analysis of the results indicates that per-pixel based supervised classification produces a large number of "salt-and-pepper" pixels, and segmentation based methods can significantly reduce this problem. However, neither method can effectively solve the spectral confusion of impervious surfaces with water/wetland and bare soils and the impacts of shadows. In order to accurately map impervious surface distribution from Quickbird images, manual editing is necessary and may be the only way to extract impervious surfaces from the confused land covers and the shadow problem. This research indicates that the hybrid method consisting of thresholding techniques, unsupervised classification and limited manual editing provides the best performance.     

基于B样条的曲面生成及加工仿真研究*

构造并生成了B样条曲面以产生给定型值点的复杂零件.以参数线加工为主要方法详细研究了该零件的加工轨迹、刀心轨迹以及切削数据的生成等;采用OpenGL技术对整个加工过程进行仿真实现,获得了一个较好的加工代码生成及轨迹验证工具.     

Impervious surface mapping with Quickbird imagery

This research selects two study areas with different urban developments, sizes and spatial patterns to explore suitable methods for mapping impervious surface distribution using Quickbird imagery. The selected methods include per-pixel based supervised classification, segmentation-based classification and a hybrid method. A comparative analysis of the results indicates that per-pixel based supervised classification produces a large number of ‘salt-and-pepper’ pixels, and segmentation-based methods can significantly reduce this problem. However, neither method can effectively solve the spectral confusion of impervious surfaces with water/wetland and bare soils and the impacts of shadows. To accurately map impervious surface distribution from Quickbird images, manual editing is necessary and may be the only way to extract impervious surfaces from the confused land covers and the shadow problem. This research indicates that the hybrid method consisting of thresholding techniques, unsupervised classification and limited manual editing provides the best performance.     

Correction of cirrus effects in Sentinel-2 type of imagery

Optical satellite images are often contaminated with cirrus clouds. Thin cirrus can be detected with a channel at 1.38 μm, and an established cirrus removal method exists for visible/near-infrared (VNIR) channels in atmospheric window regions, which was demonstrated with Moderate Resolution Imaging Spectrometer (MODIS) data. This contribution addresses open issues of cirrus correction for Sentinel-2 type of instruments, that is, future spaceborne sensors such as Sentinel-2 or similar instruments. These issues are (i) an extension of the existing technique to account for cirrus during the water vapour retrieval (channel at 0.94 μm) and surface reflectance calculation to avoid reflectance artefacts at 0.94 μm, (ii) a discussion of options concerning cirrus removal in the short-wave infrared (SWIR, channels at 1.6 and 2.2 μm) region and (iii) an analysis of channel parallax (view angle) requirements to achieve a high-quality cirrus removal.     

Machine vision system for curved surface inspection

This application-oriented paper discusses a non-contact 3D range data measurement system to improve the performance of the existing 2D herring roe grading system. The existing system uses a single CCD camera with unstructured halogen lighting to acquire and analyze the shape of the 2D shape of the herring roe for size and deformity grading. Our system will act as an additional system module, which can be integrated into the existing 2D grading system, providing the additional third dimension to detect deformities in the herring roe, which were not detected in the 2D analysis. Furthermore, the additional surface depth data will increase the accuracy of the weight information used in the existing grading system. In the proposed system, multiple laser light stripes are projected into the herring roe and the single B/W CCD camera records the image of the scene. The distortion in the projected line pattern is due to the surface curvature and orientation. Utilizing the linear relation between the projected line distortion and surface depth, the range data was recovered from a single camera image. The measurement technique is described and the depth information is obtained through four steps: (1) image capture, (2) stripe extraction, (3) stripe coding, (4) triangulation, and system calibration. Then, this depth information can be converted into the curvature and orientation of the shape for deformity inspection, and also used for the weight estimation. Preliminary results are included to show the feasibility and performance of our measurement technique. The accuracy and reliability of the computerized herring roe grading system can be greatly improved by integrating this system into existing system in the future.