Supporting Automated Pen and Ink Style Surface Illustration with B-Spline Models

This paper introduces a methodology for constructing pen and ink style landscape illustrations using B-spline surface models. Following a brief discussion of manual methods and recent developments in automated non-photorealistic rendering (NPR) techniques, the paper discusses polynomial models for surface rendering and their implementation in the OpenGL graphics interface. It then discusses the generation of silhouettes and form lines for topographic surfaces from a set of triangulated vertices obtained from polygonal tessellations. An implementation of the methodology outlined in the paper is described and tested. The results are analyzed and suggestions for further research are presented.     

Concurrent Drainage Network Rendering for Automated Pen‐and‐ink Style Landscape Illustration

Pen‐and‐ink style geomorphological illustrations render landscape elements critical to the understanding of surface processes within a viewshed and, at their highest levels of execution, represent works of art, being both practical and beautiful. The execution of a pen‐and‐ink composition, however, requires inordinate amounts of time and skill. This article will introduce an algorithm for rendering creases – linework representing visually significant morphological features – at animation speeds, made possible with recent advances in graphics processing unit (GPU) architectures and rendering APIs. Beginning with a preprocessed high‐resolution drainage network model, creases are rendered from selected stream segments if their weighted criteria (slope, flow accumulation, and surface illumination), attenuated by perspective distance from the viewpoint, exceed a threshold. The algorithm thus provides a methodology for crease representation at continuous levels of detail down to the highest resolution of the preprocessed drainage model over a range of surface orientation and illumination conditions. The article also presents an implementation of the crease algorithm with frame rates exceeding those necessary to support animation, supporting the proposition that parallel processing techniques exposed through modern GPU programming environments provide cartographers with a new and inexpensive toolkit for constructing alternative and attractive real‐time animated landscape visualizations for spatial analysis.     

基于纹理合成的三维地形水墨风格渲染研究

提出了基于纹理合成的三维地形水墨风格渲染的方法,以规则格网DEM为数据源,基于OSG进行三维地形建模,在此基础上提取山体特征线,然后生成一幅灰度控制图像。对Efros01纹理合成算法进行改进,利用灰度控制图像指导水墨纹理的合成,将得到的纹理图像映射到三维地形上,实现对三维地形的水墨风格渲染,通过对水墨纹理样本的选择和纹理合成参数的设置能够实现对纹理合成过程的交互控制。结果表明,该渲染方法对三维地形的水墨风格渲染具有较好的效果。     

Fast Image‐Space Silhouette Extraction for Non‐Photorealistic Landscape Rendering

Landscape illustration, a core visualization technique for field geologists and geomorphologists, employs the parsimonious use of linework to represent surface structure in a straightforward and intuitive manner. Under the rubric of non‐photorealistic rendering (NPR), automated procedures in this vein render silhouettes and creases to represent, respectively, view‐dependent and view‐independent landscape features. This article presents two algorithms and implementations for rendering silhouettes from adaptive tessellations of point‐normal (PN) triangles at speeds approaching those suitable for animation. PN triangles use cubic polynomial models to provide a surface that appears smooth at any required resolution. The first algorithm, drawing on standard silhouette detection techniques in surface meshes, builds object space facet adjacencies and image space pixel adjacencies in the graphics pipeline following adaptive tessellation. The second makes exclusive use of image space analysis without referencing the underlying scene world geometry. Other than initial pre‐processing operations, recent advances in the OpenGL API allow implementations for both algorithms to be hosted entirely on the graphics processing unit (GPU), eliminating slowdowns through data transfer across the system memory bus. We show that both algorithms provide viable paths to real‐time animation of pen and ink style landscape illustrations but that the second demonstrates superior performance over the first.     

基于层次包围盒的纹理体绘制加速算法

提出了一种层次包围盒(BVH)方法,以加速基于GPU的3D纹理体绘制。该方法首先利用GPU的片元着色程序实现了后分类3D纹理体绘制;然后设定高度逐层对体数据进行分解,为每个生成的子体数据建立相应的包围盒,并用对应层次包围盒树的结点保存相关信息;最后遍历层次包围盒树,读取层次包围盒树的结点信息以判断对应子体数据是否被绘制或跳过,从而实现空间跳跃,加速3D纹理体绘制。实验结果表明,本文方法与基于GPU的3D纹理体绘制算法相结合,能取得良好的加速效果。     

Automating Image Registration and Absolute Orientation: Solutions and Problems

The basic concepts and tools of automatic image registration are presented and the problems which exist are discussed. The paper describes work carried out at University College London on the registration of two images and on the registration of images with maps. It is shown that strategies have been developed which are applicable to different types of image and reference data and that with the tuning of well tried algorithms it is possible to achieve the required matching. The PAIRS technique for automatic registration of optical images from satellites has been implemented and tested and is now being developed for use with optical and microwave images. The ARCHANGEL system for registration of images with maps or vector data is also being implemented and initial results show considerable promise.     

利用遥感数据对单株木和森林场景进行建模

针对遥感在三维可视化方面的不足,提出了用SRTM(航天飞机雷达地形测图任务)和TM(陆地资源卫星专题绘图仪)数据建立森林场景的方法。利用L系统语言和L-studio软件,通过提取的分枝规则建立了针叶树和不同叶面积指数(LAI)落叶树的几何模型,并将其作为森林场景内树木的纹理贴图。实验区的三维地形用四叉树结构建立,综合应用数据分块、动态载入、双缓存数组等措施提高大范围场景的漫游速度。从TM影像获取目视判读的遥感分类图和LAI反演图,结合控制树木的栽种位置和纹理选择,建立了单幅TM影像大小的森林场景。实验为其他遥感数据的三维显示提供了通用的建模方法。     

WebGIS中草稿笔工具的实现及应用

鉴于目前WebGIS空间数据可视化表达和空间分析能力的不足,以及针对特定问题开发专门程序模块的高代价,提出在WebGIS中增加草稿笔工具(Draft Pen Tool),以作为WebGIS可视化表达和分析功能的辅助。以某矿区沉降监测数据管理信息系统为例,说明草稿笔工具在WebGIS中的作用,针对两种工作方式的基于B/S结构的WebGIS阐述该工具的编程实现方法。     

基于绘制-检出的矢量数据栅格化方法研究

对于前人提出但未被重视的绘制-检出栅格化方法进行了阐述,给出了其实现步骤与关键语句,并赋予其一个新的名称——基于绘制-检出的矢量数据栅格化方法。对该方法实现中的一些技术问题,如正确性、精度、内存位图大小限制、分块栅格化、栅格化效率等问题进行了深入的探讨。笔者认为,该方法可以成为一种普适的工业方法。     

高性能GIS动态目标渲染引擎的设计与实现

针对海量动态目标渲染效率较慢的问题,本文研究并设计了基于混合加速的高性能GIS动态目标渲染引擎,并利用SuperMap的组件GIS研发了动态目标渲染引擎原型系统.通过比较不同类型海量空间数据的可视化实验结果表明,本文研究成果在渲染二维和三维空间海量动态目标时,满足GIS高性能可视化需求,可视化效果流畅.     

一种视相关多分辨率模型及其在地形绘制中的应用

介绍了地形模型的多分辨率表示方法，提出了一种基于四叉树的多分辨率地形模型。在该模型中，采用了一种新的与视点相依赖的动态误差度量准则，对四叉树地形模型的拼接缝消除算法进行了改进，实验结果表明该模型能实现地形场景的实时游览，提高地形场景的绘制效率。     

一种视相关多分辨率模型及其在地形绘制中的应用

介绍了地形模型的多分辨率表示方法,提出了一种基于四叉树的多分辨率地形模型.在该模型中,采用了一种新的与视点相依赖的动态误差度量准则,对四叉树地形模型的拼接缝消除算法进行了改进.实验结果表明该模型能实现地形场景的实时浏览,提高地形场景的绘制效率.     

论油墨的印刷适性与地图印刷质量的关系

油墨的印刷适性是影响印刷工艺和印刷质量的主要因素之一。本文主要从地图印刷的角度出发，定性地论述油墨的主要印刷性能与印刷质量及印刷工艺的相互关系，同时，对其中一些性能提出了量化指标，以便于读者在选择印刷油墨和对印刷油墨的印刷性能进行调整与改善时，有一定的参考依据。另外，在实施印刷工艺生产中，需涉及到印刷油墨的影响时，也有一定的指导价值。     

地景模型的简化与快速绘制方法研究

在分析地景模型数据特点的基础上，提出了地景模型简化的判决准则，并根据该则提出了基于视点的区域数据抽取与简化方法以及基于法矢量的细节模型简化方法。实验结果表明，使用该方法数据压缩量大，绘制速度快，且逼真度无明显变化。     

Rendering 2D Lines on 3D Terrain Model with Optimization in Visual Quality and Running Performance

With the gradual shift from 2D maps to a 3D virtual environment, various visual artifacts were generated by overlaying 2D map symbols on 3D terrain models. This work proposes a novel screen‐based method for rendering 2D vector lines with the accuracy of more than one pixel on the screen in real time. First, screen pixels are inversely projected onto a 3D terrain surface, and then onto the 2D vector plane. Next, these pixels are classified into three categories in terms of their intersection situation with the 2D lines. After that, a multiple sampling process is applied to the pixels that intersect with the 2D lines in order to eliminate visual artifacts, such as intermittence and aliasing (in pixel scale). Finally, a suitable point‐in‐polygon judgment is implemented to color each sample point quickly. The algorithm is realized in a heterogeneously parallel model so that the performance is improved and becomes acceptable.     

面向政务地图无纸化应用的地图数据组织与渲染技术

针对政府部门工作中使用的纸质地图不方便携带、更新周期长、数据难共享的缺点,结合当前计算机技术快速发展和移动设备广泛普及的趋势,探讨实现政务地图无纸化的思路和关键技术.     

纸张毛细管分布及油墨渗透的研究

基于纸张毛细管气孔的容积和纸张毛细管对液体的吸收等，提出了研究纸张毛细管分布的一种方法，并在此基础上，分析了油墨的渗透现象和渗透深度。     

喷墨印刷平面呈色模型的建立与检验

采用插值算法,提出了一种新的平面呈色模型建立方法,实现喷墨印刷中L*a*b*与cmy颜色空间之间的转换,并对转换精度进行了检验分析。本研究通过比较喷墨打印和胶印的平面呈色模型,为在各种印刷方式中建立平面模型提供了成功的范例和切实可行的方法。     

基于OSG的火星形貌3维建模与绘制

开展了基于开源3维渲染引擎OSG(OpenSceneGraph)的火星形貌3维建模与绘制的研究.使用地形数据库创建工具VPB(VirtualPlanetBuilder)创建了整个火星的分页数据库,并利用基于OSG的仿真平台实现了火星形貌数据的3维可视化.实验结果证明,该方法能很好地处理海量地形数据,完成火星形貌的3维重...