CN100468461C - Real time drawing method of vivid three dimensional land form geograpical model - Google Patents

Real time drawing method of vivid three dimensional land form geograpical model Download PDF

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CN100468461C
CN100468461C CN 200510086833 CN200510086833A CN100468461C CN 100468461 C CN100468461 C CN 100468461C CN 200510086833 CN200510086833 CN 200510086833 CN 200510086833 A CN200510086833 A CN 200510086833A CN 100468461 C CN100468461 C CN 100468461C
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terrain
data
cache
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刘贤梅
逊 史
王莉莉
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北京航空航天大学
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Abstract

逼真三维地形几何模型的实时绘制方法,其特征在于包括下列步骤:(1)地形数据预处理,使地形数据结构符合本方法后续部分的操作;(2)采用基于传统LRU算法与基于视点兴趣相结合的方法进行文件间的实时切换的地形调度算法,完成对大规模地形文件的实时调度;(3)基于几何的Mip Map地形网格实施生成算法,简化地形模型;(4)基于多纹理的GPU地形BumpMap渲染算法,显示地形特征;(5)基于四叉树的遍历的地形局部替换算法,实现地形数据变换。 The method of realistic real-time rendering three-dimensional geometric model of the terrain, comprising the steps of: (1) pre-terrain data, terrain data structure so that the operation and subsequent portions of the present method; (2) conventional LRU algorithm based on viewpoint and with interest the method of scheduling algorithms bound terrain real-time switching between files, complete real-time scheduling for large scale terrain file; (3) Mip Map generation algorithm embodiment terrain mesh geometry, simplified terrain model; (4) based on multi-texture terrain BumpMap GPU rendering algorithms, show terrain features; (5) replacement algorithm based on local topography quadtree traversal, terrain data conversion achieved. 本发明解决了地形模型绘制速度慢的问题,提高了绘制效率,达到了动态地形的实时绘制目的。 The invention solves the terrain model problem of slow rendering speed, improved rendering efficiency, achieve the purpose of real-time rendering of dynamic terrain.

Description

逼真三维地形几何模型的实时绘制方法 Methods realistic real-time rendering three-dimensional geometric model of the terrain

技术领域 FIELD

本发明涉及一种三维地形几何模型的实时绘制方法。 The present invention relates to a method for real-time rendering of three-dimensional terrain geometry model. 背景技术 Background technique

地形绘制技术主要包括地形资源数据组织、绘制数据组织以及绘制过程中具体采用的绘制方法,地形资源数据组织是指对获取的地形数据的存储方式。 Terrain rendering resource data includes topographical organization, organizational drawing method and drawing data using the drawing process specific, topographical organization resource data storage means of the acquired terrain data. 根据地形数据获取手段不同,典型的地形数据以等距的地表高程网格 According to the different means of access to terrain data, terrain typical of the surface elevation data in an equidistant grid

DEM采样,如图1a所示,这部分数据未经面向绘制的优化处理,数据量大, 冗余,但数据精度好,经常应用在科学计算或军事方针中。 DEM sample, shown in Figure 1a, without this part of the data optimization processing for drawing, the amount of data, redundancy, but better data accuracy, often used in the scientific computing policy or military. 绘制数据组织将得到的弟子那个资源数据面向绘制的进行重新组织,这样做的目的是在不影响显示效果和逼真性的基础上尽量减少绘制定点数量和提高绘制效率。 Drawing data organization will get a disciple of the resource data for the re-organization of the draw, the purpose of this is without prejudice to minimize the number of fixed-point draw drawing efficiency and improve the display and on the basis of realism. 该阶段的数据组织一般根据生成几何面片的特点分为规则网格和不规则网格,一是基于四叉树结构的筒化算法,重构后的数据格式成四边形或规则三角形的阵列分布,如图化所示;二是基于三角网的简化算法,重构后的数据格式成不规则三角形的阵列分布,如图1c所示。 The data organization according to the general characteristics of the phase generating geometric surface, divided into a regular grid sheet and irregular grid, one based on the distribution cylinder array quadtree algorithm structure, data format reconstructed into a regular triangular or quadrangular , as shown in FIG oriented; Second triangulation algorithm based on simplified data format reconstructed into an irregular array of triangular distribution shown in Figure 1c. 前者速度快,但是简化效果不如后者,后者的效果应该可以达到最优,但速度却要比前者慢一个甚至几个数量级。 The former is fast, but not as good as the effect of simplifying the latter, the latter should be able to achieve the optimal effect, but the speed has to slower than the former one or even several orders of magnitude. 绘制方法是指将经过优化后的地形数据通过OpenGL或DirectX等绘制平台经过显卡绘制到显示屏上。 After rendering method refers to terrain data and the like by optimized DirectX or OpenGL graphics rendering platform is drawn onto the display screen.

目前国外公开的文献中,Lindstrom P, Koller D, Ribarsky Wetal. "Real-Time continuous level of detail render of height fields" In SIGGRAPH, 96Proc, New Orleans, Louisiana USA,1996.较早给出了四叉树结构的实时地形简化算法。 Current foreign published literature, Lindstrom P, Koller D, Ribarsky Wetal. "Real-Time continuous level of detail render of height fields" In SIGGRAPH, 96Proc, New Orleans, Louisiana USA, 1996. Quadtree given earlier Real-time structure of the terrain simplification algorithm. 国内王宏武,"一个与视点相关的动态多分辨率地形模型",计算机辅助设计与图形学报,2000, 12(8)提出了基于多分辨率地形模型的视点相关模型;潘李亮,"基于LOD的大规模真实感室 China Wang Hongwu, "a viewpoint associated with dynamic multi-resolution terrain model," Computer-Aided Design and Graphics, 2000, 12 (8) put forward the view-dependent model of multi-resolution terrain model based; Liang Pan, "based on the LOD large-scale realistic room

外场景实时渲染技术的初步研究"中国游戏开发网2003.4提出了使用了视点相关以及和地形本身起伏程度相关的技术来决定地形应有的细节程度的LOD算法。 Preliminary studies and outdoor scenes real-time rendering technology, "China Game Development Network 2003.4 proposed the use of a relevant degree as well as view and undulating terrain itself relevant techniques to determine the level of detail of the terrain due LOD algorithms.

但上述文献的解决思路有三个缺陷:第一,没有考虑到大规模地形的优化问题,大规模地形仿真是仿真应用中常见的需求,但是对大规模地形装载一般都采用一次装载所有地形,或简单采用LRU (最近最少使用次数)算法进行描述,从根本上没有考虑到使用者对于地形漫游时的运行特点;第二, 没有考虑到地形的逼真渲染,地形的逼真渲染是现实的逼真性和数据复杂度矛盾中和的结果,即如何用尽量少的数据描述逼真的地形效果。 But ideas to solve the above document has three shortcomings: First, do not take into account the optimization of large-scale terrain, terrain simulation of large-scale simulation applications is common needs, but large-scale terrain loader is generally used once to load all terrain, or using simple LRU (least recently used frequency) algorithm description, fundamentally not take into account the characteristics of the user running for the terrain roaming; second, without taking into account realistic rendering of the terrain, the terrain is realistic rendering of reality and verisimilitude data complexity and contradiction result that as few data describing how realistic terrain effects. 比较经典的 More classic

问题包括,三角网格的简化、T型裂缝的消除、逼真紋理的加载等。 Problems include simplified triangular mesh, T-eliminating cracks, realistic texture, such as load. 在面向现实设备的编程中,三角形的生成一般采用三角形列表或三角形条带生成算法(Deering Michael, "Geometry Compression" Computer Graphics, pp. 13-20, August 1995)。 In real programming device for generating a list of triangles generally triangular or triangle strip generation algorithm (Deering Michael, "Geometry Compression" Computer Graphics, pp. 13-20, August 1995). 其中随着图形显示设备功能的日益强大,采用GPU (Graphic Processing Unit,图形设备中的一种硬件结构)进行快速的顶点计算和紋理加载成为渲染的重要工具,将其应用到地形的绘制中近年来还比较少;第三,没有考虑到地形数据动态更新,地形在显示过程中并非一成不变, 一般会由于如爆炸等特殊原因产生地形顶点位置的变化,如何将这些变化在通用的图形系统上得以实现,上述的文献均没有予以考虑。 With the graphical display in which increasingly powerful equipment functions, the use of GPU (Graphic Processing Unit, a piece of hardware in the graphics device structure) for rapid calculation of vertex and texture rendering load become an important tool, apply it to Terrain Rendering in recent years to the still relatively small; third, without taking into account the dynamic update terrain data, terrain not fixed in the display process, will generally produce a change of position of the apex a special reason such as terrain explosion, and how these changes will be on a general purpose graphics system to achieve the above documents are not taken into account. 因此,造成目前三维地形几何模型时,绘制速度緩慢、绘制效率低,实时逼真绘制效果差的缺陷。 Thus, resulting in the current three-dimensional terrain model geometry, slow rendering speed, low rendering efficiency, real-time realistic rendering ineffective defects. 发明内容 SUMMARY

本发明的技术解决问题:克服现有技术的不足,提供一种逼真三维地形几何模型的实时绘制方法,该方法解决了地形模型绘制速度慢的问题,提高了绘制效率,达到了动态地形的实时逼真绘制目的。 Technical present invention to solve the problem: to overcome the disadvantages of the prior art by providing a method of realistic real-time rendering three-dimensional geometric model of the terrain, terrain model which solves the problem of slow rendering speed, improved rendering efficiency, achieve real-time dynamic terrain realistic rendering purposes.

本发明的技术解决方案:逼真三维地形几何模型的实时绘制方法,其特 Technical solutions of the present invention: The method of realistic real-time rendering three-dimensional geometric model of the terrain, which Laid

(1 )地形数据预处理,筒化地形数据结构; (1) pretreatment terrain data, terrain data structure of the cartridge;

(2) 采用基于传统LRU算法与基于视点兴趣相结合的方法进行文件间的实时切换的地形调度算法,完成对地形文件的实时调度; (2) The scheduling algorithm for real-time switching of the terrain between files based on conventional LRU algorithm and the viewpoint based on the combination of interest, complete real-time scheduling of the terrain file;

(3) 基于几何的Mip Map地形网格实施生成算法,简化地形模型; (3) Embodiment Mip Map Generation Algorithm for terrain mesh geometry, simplified terrain model;

(4) 基于多紋理的GPU地形Bump Map渲染算法,显示地形特征; (4) GPU topographic Bump Map Texture rendering algorithms based on multi-display topographical features;

(5) 基于四叉树的遍历的地形局部替换算法,实现地形数据变换。 (5) replacement algorithm based on local topography quadtree traversal, terrain data conversion achieved. 所述的地形数据预处理的步骤如下: The terrain data preprocessing step as follows:

(1 )对原始文件数据文件分割; (1) dividing the original document data file;

(2)将分割后的文件重排,即将分割后的文件组按照地理信息重新命名,并保存在文件系统中。 (2) the divided files rearrangement, the group soon split files by geographic information renamed and saved in the file system. - -

本发明使用的地形数据源于GTOPO30地形数据(具体信息、格式、使用权限参见USGS 的操作手册网站咖:〃edcdaac.usqs.qov/。toiX)30/README.asp ),该地形包含全玉求1000 米精度的地形高度数据,16位采样精度,将全球分为若干个区块,每区块大小6000*4800个采样点。 Terrain data from the present invention for use terrain data GTOPO30 (USGS see specific information, formats, usage rights operating manual coffee website: 〃edcdaac.usqs.qov / .toiX) 30 / README.asp), which consists of all terrain Yu seek 1000 m terrain height data accuracy, 16-bit sampling accuracy, the world's divided into several blocks, each block size 6000 * 4800 sampling points. 将这样的一块原始数据调入内存后数据量巨大难以实现实时操作,同时6000公里的范围远远超出人的视域范围。 Such a raw data into memory after a huge amount of data that is difficult to achieve real-time operation, while 6,000 km range far beyond the range of human sight. 因此, 必须对这些原始文件进行分割重排。 Therefore, you must divide the rearrangement of these original documents. 文件分割是将文件大小由6000*4800 降为512*512或更小256*256,这里取2的幂次大小是为了加快系统的处理速度(由于计算机采用2进制计算),而幂值的大d、一般根据应用需求和机器性能决定。 File dividing the file size down to 512 by the 6000 * 4800 * 512 256 * 256 or less, where the size of a power of 2 is taken in order to accelerate the processing speed of the system (due to the use of computer-calculated binary), the value of the power large d, is generally determined by the machine performance and application requirements. 重排是将分割后的文件组按照地理信息重新命名,并保存在文件系统中。 Rearrangement is divided according to geographical information file group renamed and saved in the file system. 由于GTOPO30的原始文件包含具体的经炜度信息,重排的过程就可以借助这些信息获得分割后的文件的起始经绵度。 Since the original document GTOPO30 by Wei contain specific information, the rearrangement process can start by means of soft information file obtained after division. 根据这些信息可以命名文件,形如:gtopo30—E120—N40.dem表示东经120度,北炜40度为起点的地形数据。 These files can be named according to the information, the form: gtopo30-E120-N40.dem 40 degrees North Wei terrain data is represented as the starting point longitude 120 degrees.

所述的地形调度算法步骤如下: The scheduling algorithm terrain following steps:

(1 )取当前的视点位置及朝向,分析可视数据地形块; (1) take the current viewpoint position and the orientation of visual data analysis block terrain;

(2) 根据当前地形缓存数据和可视地形块数据更新地形緩存列表,生成下一帧数据; (2) update the cache list according to the current topographic terrain topography and visual data cache block data, generating a next frame of data;

(3) 緩存的更新。 (3) cache updates.

地形经过预处理后虽然变成较小的文件组,但同时将这些文件调入内存仍还不切实际,还需要进行动态调度。 Although the terrain after pretreatment group becomes smaller files, but these files into memory still remains unrealistic, but also the need for dynamic scheduling. 由于人的试点的移动是有规律的,以及可视范围的限制,由于传统的LRU没有考虑试点漫游过程中的反复特点, 本发明在LRU的基础上对算法进行了改进,采用基于传统LRU算法与基于视点兴趣相结合的方法进行文件间的实时切换的地形调度算法。 Due to movement of the pilot who is regular, and the visible range limit, since the conventional LRU without considering pilot repeated during roaming features, the algorithm of the present invention is improved based on the LRU, LRU algorithm traditional terrain scheduling real-time switching between files based on a combination of interest viewpoints.

上述緩存的更新步骤如下: The above-described cache update is as follows:

a. 緩存中每一块数据都有一个使用次数的统计,若下一帧需要的地形快存在于緩存中,则该统计项自动加一; . A data cache, each block has a number of usage statistics, if a next frame exists in the required terrain faster cache, the corresponding entry is automatically incremented;

b. 根据当前视点和朝向和上一帧的试点和朝向进行比较,得出下一帧指向的数据,若该数据存在于缓存中,则统计项自动加一; . B according to the current viewpoint and orientation and a pilot orientation and comparison, the data points to the next frame, if the data exists in the cache, the item is automatically incremented count;

c. 在此基础上,将需要但不存在的数据添加到緩存中,并将同样数量的数据从当前緩存中剔出,原则是选择当前缓存中统计项最小的数据,但不能使本次命中的; c. Based on this, but there is no need to add the data to the cache, and the same amount of data excised from the current cache, the principle is to select the smallest current data item in the cache statistics, but you can not make this hit of;

d. 若剔出的数据少于增加的数据,即緩存太小,则增加緩存数量; . D excised If data is less than the increase of data, i.e. the buffer is too small, increasing the cache;

e. 若没有要剔出的数据,则每一帧自动将当前緩存中的统计项最小的数据块剔出,并将当前緩存大小减一, 一次保持緩存不会无限制增加; . E Without to be bound by data, each frame is automatically statistical item minimum current data block in the cache excised, and a Save current cache size, the cache will not be increased without limit holding time;

f. 若系统继续工作,则返回重复c,否则终止。 f. If the system continues to work, then return to repeat c, otherwise terminated. 所述的基于几何的Mip Map地形网格实施生成算法步骤如下: Generation algorithm according to embodiments based on the following steps Mip Map terrain mesh geometry:

(1 )对于新加入的地形块,将数据组成四叉树结构,统计每一地形片顶点中的最大,最小,误差等参数; (1) Add a new terrain to block, the composition of the quad-tree structure data, the statistics for each parameter in the terrain patch vertices maximum, minimum, error or the like;

(2) 根据当前视点和地形块包围球中心的距离,判断采用哪一精度级别的四叉树数据; (2) surrounds the center of the ball block of the current viewpoint and terrain distance, which determines the level of precision using a quadtree data;

(3) 根据相邻的地形片数据精度级,'生成地形三角形条带,消除T型突起; (3) The sheet adjacent topographical data precision level, 'generates terrain triangle strips, eliminating T-shaped protrusion;

(4) 将三角形条带输入到GPU,进行平滑处理。 (4) The triangle strip input to the GPU, the smoothing process.

地形文件包含地形采样点的几何信息,这些信息将地形描述为一个大的网格。 Terrain file contains the geometric information terrain sampling points, terrain information will be described as a large grid. 在实施绘制过程中,网格被三角化为Triangle List或Triangle Strips 送入渲染管道以优化渲染速度。 In the embodiment of the drawing process, into a triangular grid is Triangle List or Triangle Strips fed rendering pipeline to optimize the rendering speed. 即便如此,显示速度特别是在多个地形文件显示的情况下仍不能满足需求,因此就需要进一步优化。 Even so, the display speed still can not meet demand especially in the case of multiple documents show the terrain, and therefore need to be further optimized. 本发明采用的方法是基于几何的MipMap网格生成算法,将每一个地形文件在内存中形成四叉树的组织结构,底层为17*17个顶点组成的Data Patch,上一层包含4个下层子树,递归生成直至包含文件全部顶点。 The method of the present invention is employed to generate MipMap mesh geometry based on the algorithm, each of the terrain file organizational structure quadtree form in memory, the bottom 17 of the vertices 17 * Data Patch, the lower layer contains 4 subtree, recursively generated until all the files containing the vertex. 对于256*256的地形文件, 这样的一颗树包含的子树层数为5层,每一层代表该Data Patch的一种精度。 For terrain file 256 * 256, the number of layers of such a sub-tree comprising a tree of five layers, each layer represents one of the accuracy of the Data Patch. 在生成四叉树的过程中需要计算每一层地形数据的方差,平均高度等信息,这些信息在实时显示过程中根据视点到地形中心的距离选择某一粗糙度级别的数据。 You need to calculate the variance of each layer in the process of generating the terrain data quadtree average height information, topographic information from a center to a selected roughness viewpoint level data in accordance with real-time display process. 当从一个粗糙级别调到另一个粗糙级别时,屏幕上会产生跳变; 而当相邻的地形粗糙程度不同时会在交界处产生所谓的裂缝问题,解决这个问题需要用到GPU的Shader代码。 When transferred from one level to another rough coarse level transition is generated on the screen; and if the code Shader adjacent terrain roughness and it will produce a so-called no cracks at the junction, to solve the problem of the need to use GPU .

所述的基于多紋理的GPU地形Bump Map渲染算法步骤如下: The GPU-based terrain rendering algorithms Bump Map Texture many steps as follows:

(1) 据地形块数据生成凹凸贴图的向量图和地表地貌图,该算法是在运行前预处理阶段完成的; (1) According to the block data to generate topographic surface topography and vector diagram of FIG bump map, the algorithm is done in the pretreatment stage before running;

(2) 计算地表平面法向量; (2) Calculation of Surface plane normal vector;

(3 )根据顶点数据所在平面法向量计算顶点的法向量; (3) The vector plane normal vector calculated based on the vertex data of the vertex is located;

(4 )将法向量存储在文件中作为本算法的凹凸贴图法向紋理输入; (4) The normal vector stored in a file as a bump map texture to the method of the present algorithm is input;

(5) 根据地形顶点的高度,计算该定点使用地表紋理的权值; (5) The elevation of the terrain vertices, the point is calculated using the weight of the surface texture;

(6 )利用GPU的像素处理单元(Pixel Shader)合成紋理并计算光照; (7)进行bump贴图算法。 (6) utilizing a GPU the pixel processing unit (Pixel Shader) synthesized texture and lighting calculations; (7) bump mapping algorithm.

(1 )获取待替换地形地理位置; (1) obtaining geographic terrain to be replaced;

(2) 根据上述的地形位置索引四叉树; (2) According to the quadtree topographic location index;

(3) 更新局部地形数据; (3) update the local terrain data;

(4) 重新计算法向量信息。 (4) recalculating normal vector information.

本发明与现有技术相比的优点在于: Advantages over the prior art in that the present invention:

(1) 针对高精度地形高程数据规模大,不能一次性调入内存的问题, 按照区域将地形数据分割为多个文件,保存在文件系统中或数据库系统中, 采用基于传统LRU算法与基于视点兴趣相结合的方法进行文件间的实时切换、调度,达到了灵活有效管理大规模地形数据的效果; (1) terrain elevation data for the large-scale high-precision, not a one-time transferred to memory problems, according to the terrain data area is divided into a plurality of files stored in the file system or database system, based on conventional LRU algorithm and the viewpoint interest method of combining live switching between files, scheduling, achieve the effect of a flexible and efficient management of large-scale terrain data;

(2) 针对三维地形几何模型顶点数据量大,绘制速度慢的问题,在建立树状数据结构的基础上,使用基于几何的mipmap方法,根据视点和局部地形特点实时形成最少数量的顶点,并借助基于硬件的顶点切换算法对因视点改变引起的地形跳变进行平滑处理,达到了地形模型绘制效果和绘制速度的良好平衡; (2) three-dimensional terrain geometry model for the vertex data volume, the problem of slow drawing speed, on the basis of the establishment of the tree data structure, using the geometric method based mipmap, the minimum number of vertices is formed according to the viewpoint in real time and the local terrain features, and by means of hardware switching algorithm based on vertex viewpoint changes caused by the terrain hopping smoothing process, to achieve a good balance of the effect of terrain rendering speed and rendering model;

(3) 针对现有地形地貌特征复杂,完全使用几何面片描述,难以保证其逼真性和绘制的实时性的问题,采用了基于多紋理的GPU地形渲染方法, 并通过凹凸贴图算法和紋理混合,将基本地貌紋理和文化特征紋理进行实时融合,既达到逼真显示的效果,也提高了绘制效率; (3) wherein the existing topography complicated geometric surface sheet fully described, it is difficult to guarantee real-time rendering and fidelity problems, using a multi-GPU texture based terrain rendering, and mixed by a bump mapping algorithm and texture the basic features of the landscape and cultural texture textures for real-time integration of both achieve realistic display, but also improve the rendering efficiency;

(4) 针对地形绘制中需要动态改变局部顶点坐标的应用需求,采用基于四叉树的遍历,定位局部顶点数据,借助基于图形硬件的插值算法实现更新后的数据与周围环境数据的融合,以达到动态地形的实时绘制目的。 (4) for terrain rendering dynamically changing application requirements local vertex coordinates, based traversal of the quadtree, locating local vertex data, means based on the graphics hardware interpolation algorithm to update the data with the surrounding environmental data fusion, to to achieve the purpose of real-time rendering of dynamic terrain. ' 附图说明 'BRIEF DESCRIPTION

图1为现有地形数据基本组织结构图,其中图1a为典型的地形数据以等距的地表高程网格DEM采样图,图1b为基于规则三角形化阵列分布图, 如图1b所示,图1c为不规则三角形的阵列分布图; 图2为本发明的大规模地形调度算法模块结构图; 图3为本发明的基于几何的Mip Map地形网格简化示意图; FIG 1 is a conventional topographic data base organization chart, in which Figure 1a is a typical terrain elevation data in an equidistant grid DEM sample surface, and FIG. 1b based on an array of regular triangular profile, shown in Figure 1b, FIG. 1c is an array of irregular triangular profile; Large scale terrain scheduling algorithm module configuration diagram of the present invention. FIG. 2; Mip map based on a simplified schematic diagram of FIG. 3 terrain mesh geometry of the present invention;

图4为本发明的消除T型突起示意图; 4 of the present invention eliminates a schematic view of FIG. T-shaped protrusion;

图5为本发明的基于多紋理的GPU地形Bump Map渲染算法示意图; FIG 5 a schematic topographic Bump Map rendering algorithm based on multi-GPU texture of the present invention;

图6为本发明的基于四叉树的遍历的地形局部替换算法示意图。 FIG 6 is a schematic view of the algorithm based on the disclosure of alternative local terrain traversal of the quadtree. 具体实施方式 Detailed ways

下面结合实施例对本发明进一步详细说明。 Below in connection with embodiments of the present invention will be described in further detail.

以当前反映中国地形的原始DEM数据文件,横纵为1024*1024个顶点为例。 To reflect current raw data file China DEM terrain, vertical and horizontal 1024 * 1024 vertices example.

1. 首先进行预处理,对数据文件进行分割,该文件被分割为256*256 大小的文件序列组,再将分割后的文件组按照地理信息重新命名,并保存4 个地形文件中,假设文件a,b, c, d。 1. First pretreatment, dividing the data file, the file is divided into a sequence of file group 256 * 256 size, the file group and then divided by geographic information renamed and stored terrain file 4, assume the file a, b, c, d.

2. 然后采用基于传统LRU算法与基于视点兴趣相结合的方法进行文件间的实时切换的地形调度算法,完成对地形文件的实时调度。 2. The scheduling algorithm then uses topographic switching between real-time file based on conventional LRU algorithm and the viewpoint based on the combination of interest, complete real-time scheduling of the terrain file. 传统的LRU 算法考虑最近最少使用的地形信息,当緩冲中没有空间时,将最近最少使用的地形块剔出内存。 Conventional LRU algorithm considering topographic information of the least recently used when there is no buffer space, the terrain blocks least recently used memory excised. 这种方法广泛使用在内存调度程序中,但没有考虑到地形浏览过程中的特点。 This method is widely used in the memory scheduler, but without taking into account the characteristics of the terrain browsing process. 当人们位于某一视点,并且按某一路线进行运动时, 总可以根据运动的方向预测下一帧视点的位置,根据兴趣,视点可以转动, 这就增加了预测的复杂性。 When people located in a viewpoint, and according to a motion path can always be predicted position of the next frame according to the viewpoint direction, according to the interest, the viewpoint can be rotated, which increases the complexity of the prediction. 本发明结合视点运动兴趣的LRU算法,可以将这种预测融入算法中。 LRU algorithm of the present invention in conjunction with movement of the viewpoint of interest, which can be integrated into the prediction algorithm. 如图2所示,地形调度算法如下: 2, the terrain scheduling algorithm is as follows:

(1) 绘制程序启动,初始化地形数据緩存,预载入原点附近的地形数据;初始时,原点位于文件a所在地域,且此时视点能及的范围仅为a地域, 则初始化的地形緩存中仅存储a的数据信息; (1) drawing program starts, initialization terrain data cache, pre-loaded terrain data near the origin; initially, a file area where the origin is located, and at this time, and can view only a geographical range, the initialization terrain cache storing only a data information;

(2) .获取当前的视点位置及朝向,分析可视数据地形块;显示过程中, 假若视点位于a, b交界处,此时可是内容包含a, b两块地形数据; (2) Get current viewpoint position and orientation, topographic analysis of visual data block; is displayed, if the viewpoint is located in a, b at the junction, but now contains the contents a, b two topographical data;

(3) 根据当前地形緩存数据和可视地形块数据更新地形緩存列表,由于b地形数据此时并不在緩存之中,因此算法将装载b数据到緩存中。 (3) The current terrain data cache block updated and visualized topographic terrain data cache list, since the terrain data b in this case is not a cache, so the algorithm to load the data into the buffer b. 生成下一帧数据;(4)緩存的更新是本发明中的重点,具体步骤如下: Generating the next frame; (4) updates the cache is the focus of the present invention, the following steps:

a. 緩存中每一块数据都有一个使用次数的统计,若下一帧需要的地形快存在于緩存中,则该统计项自动加一; . A data cache, each block has a number of usage statistics, if a next frame exists in the required terrain faster cache, the corresponding entry is automatically incremented;

b. 根据当前视点和朝向和上一帧的试点和朝向进行比较,根据趋势预测出下一帧可能的数据,若该数据存在于缓存中,则统计项自动加一; . B according to the current viewpoint and orientation and a pilot orientation and comparing predicted next frame based on trends possible data, if the data exists in the cache, the item is automatically incremented count;

c. 在上述a、 b的基础上,将需要但不存在的数据添加到緩存中,并将同样数量的数据从当前緩存中剔出,原则是选择当前缓存中统计项最小的数据,但不能使本次命中的; c. On the basis of the above a, b on, but there is need to add the data to the cache, and the same amount of data from the current buffer excised in principle to choose a minimum data items currently in the cache statistics, but not make this a hit;

d. 若剔出的数据少于增加的数据(即緩存太小),则增加緩存数量, 一般增加一倍,即当前缓存大小仅为1块地形,而由于a, b都在被显示, 而緩存数量必须增加,增加策略为2倍于原始大小,若原始大小为4块地形, 则增加后的地形大小为8块; d. If data less bound by the increased data (i.e. cache is too small), the number of buffers is increased, typically doubled, i.e. the current buffer size of only one terrain, and as a, b are to be displayed, and the number of buffers must be increased to increase the policy twice its original size, if the size of the original four terrain, terrain increase of size 8;

e. 若没有要剔出的数据,则每一帧自动将当前缓存中的统计项最小的数据块剔出,并将当前緩存大小减一, 一次保持緩存不会无限制增加; . E Without to be bound by data, each frame is automatically statistical item minimum current data block in the cache excised, and a Save current cache size, the cache will not be increased without limit holding time;

f. 若系统继续工作,则返回重复c,否则终止。 f. If the system continues to work, then return to repeat c, otherwise terminated.

3.基于几何的Mip Map地形网格实施生成算法,简化地形模型,如图3 、图4所示,具体步骤如下: 3. The embodiment terrain mesh geometry based Mip Map generation algorithm, a simplified model of the terrain, as shown in FIG 3, FIG. 4, the following steps:

(1 )将地形调度算法中步骤(4)后的地形数据块形成列表并对每一块循环进行如下操作; (1) The scheduling algorithm topographic terrain data block after step (4) is formed and a list of the following steps for each one cycle;

当初次加入地形b后场景图中并没有相应的绘制对象(具体包含绘制地形、紋理的数据和状态),因此系统此时将建立相应的绘制对象:将每一个地形文件在内存中形成四叉树的组织结构,底层为17* 17个顶点组成的Data Patch,上一层包含4个下层子树,递归生成直至包含文件全部顶点。 Was added after the original topographic b scene graph objects not corresponding drawing (particularly containing terrain rendering, texture data and status), and therefore at this time the system will establish a corresponding drawing object: each of the terrain file is formed in memory quad organization tree, the bottom 17 of the vertices 17 * Data Patch, a layer comprising four lower subtree, recursively generated until all the files containing the vertex. 对于256*256的地形文件,这样的一颗树包含的子树层数为5层,每一层代表该Data Patch的一种4青度。 For terrain file 256 * 256, the number of layers of such a sub-tree comprising a tree of five layers, each layer represents one of the four Data Patch of green.

(2) 对于新加入的地形块,将数据组成四叉树结构,统计每一Data Patch顶点中的最大,最小,误差等参数; (2) newly added for the terrain blocks, the quad-tree structure composed of data, the statistics for each vertex parameters Data Patch maximum, minimum, error or the like;

(3) 根据当前视点和地形块包围球中心的距离,判断采用哪一精度级别的四叉树数据;建立绘制对象后,该地形模型即可进行正常绘制。 (3) based on the current viewpoint and the terrain surrounding the block from the center of the sphere, is determined using the quadtree which data precision level; after establishing the drawing object, the normal terrain model can be drawn. 绘制时首先需要确定采用那个精度的数据送去显示,这是十分必要的优化过程。 First need to determine the accuracy of data sent using the display as you draw, it is necessary to optimize the process. Data Patch从最粗糙(0级)到最精细(n级),顶点数量相差2A(n-1 )倍, 在视点误差满足的情况下选择相对粗糙的精细级别在大规模数据的情况下可以大大减轻系统压力,从而从根本上提高绘制速度。 Data Patch from the coarsest (0) to the most sophisticated (n stages), the number of vertices differ 2A (n-1) times, in a case where the viewpoint selected error satisfies relatively coarse level of granularity in the case of large-scale data can be greatly relieve system pressure, thereby increasing the speed of rendering fundamentally. 视点误差的判断有多种,如基于投影空间、基于屏幕空间等,由于相应算法很多,具体算法不在本发明保护范围。 There are many error judges viewpoint, such as the projection space, based on the screen space, since many corresponding algorithm, not specific algorithm scope of the invention.

(4) 根据相邻的地形片数据精度级,生成地形三角形条带,消除T型突起;当相邻Data Patch的精细级别不同时会由于相邻的顶点不对应而产生T型突起,该问题的解决可以通过本方法解决:假设Patch 1和Patch 2 相邻且精细级别分别为2和3。 (4) precision level, generating terrain triangle strips, according to eliminate the T-shaped projection pieces adjacent terrain data; Data Patch adjacent fine level can not simultaneously generated since the adjacent vertices does not correspond to when the T-shaped projection, the problem solution can be solved by this method: Suppose Patch 1 Patch 2 and the adjacent and finely levels 2 and 3, respectively. 由于3级更加精细,为了保证显示质量,令Patch2与之相邻的三角形定点选择3级精度,其余不变,这样生成的三角形条带可以较好的解决T突起问题,同理,相邻地形文件间的Patch也采取此法消除T突起。 Since finer grade 3, in order to ensure the display quality, so Patch2 adjacent triangles pointing accuracy selection stage 3, remaining unchanged, the triangle strip thus formed can be better solved the problem projections T, is, the adjacent terrain Patch files can take between this method to eliminate T protrusions.

(5) 将三角形条带输入到GPU,进行平滑处理。 (5) The triangle strip input to the GPU, the smoothing process.

4.如图5所示,进行基于GPU的多层紋理融合的凹凸贴图步骤如下: 运行前需要根据地形的顶点信息生成地形向量信息,即每个地形顶点处的法向量,还需要由美工给出地表特征数据文件。 4. FIG. 5, step bump map based on a multilayer GPU texture blending as follows: The vector information needs to be generated topographic terrain before running vertex information, i.e., the normal vector at each vertex of the terrain, but also by the art to the surface feature data file. 法向量求法:先求出顶点所在平面的平面法向量,然后再根据平面法向量的平均求出该顶点的法向量。 Seeking normal vectors: first determined plane of the vertex normal vector of the plane, then the normal vector of the vertex plane method based on the average vector is obtained. 地表特征数据文件记录对应地表每个顶点使用原始紋理的信息。 Surface characterization data file corresponding to the information recording surface of each vertex of the original texture. 本发明支持3路并发的原始紋理,每个顶点可以任选其一,或者给出三者的各自比例的权值。 The present invention supports the original texture of concurrent 3, each vertex may optionally one or weights are given respective proportions of the three.

(1 )根据地形块数据生成凹凸贴图的向量图和地表地貌图,这是在运 (1) generating a bump map surface topography and vector diagram according to FIG terrain data block, which is in operation

行前预处理阶^:完成的; ^ Pretreatment step forward: completed;

(2)计算地表平面法向量; (2) Calculation of Surface plane normal vector;

(3 )根据顶点数据所在平面法向量计算顶点的法向量; (3) The vector plane normal vector calculated based on the vertex data of the vertex is located;

(4 )将法向量存储在文件中作为凹凸贴图法向紋理输入; (4) The method to store the input vector in the texture file as bump mapping method;

(5)根据地形顶点的高度,计算该定点使用地表紋理的权值。 (5) The elevation of the terrain vertices, the point calculating weights using the surface texture. 可以实 Can be achieved

时输入3个地表紋理,这里的权值就是该顶点使用三个地表紋理的比重,并 When the input three surface texture, where the weight value is the apex of the three surface texture using gravity, and

将权值记录在单独的文件中作为紋理参数输入; The weights recorded as the texture parameters entered in a separate file;

(6 )利用GPU的像素处理单元(Pixel Shader)合成紋理并计算光照。 (6) utilizing a GPU the pixel processing unit (Pixel Shader) synthesized texture and lighting calculations.

紋理合成:最终颜色=紋理1颜色*紋理1权值+紋理2颜色*紋理2权值+紋 Texture synthesis: Final Color * 1 Color Texture = Texture Texture 2 1 + Weight * color + texture grain weight 2

理3颜色"丈理3权值; 3 color management "processing 3 feet weight;

(7)进行采用bump贴图算法(该算法是成熟的算法)。 (7) use of bump mapping algorithm (the algorithm is sophisticated algorithms).

5.如图6所示,基于四叉树的遍历的地形局部替换算法步骤如下: 5. As shown, based on local topography quadtree traversal algorithm steps 6 replaced as follows:

(1) 获取待替换地形地理位置,即获得地形起始顶点的经纬度信息, 根据该信息,可以获得该地形数据在四叉树中的位置; (1) obtaining geographic terrain to be replaced, i.e., latitude and longitude information obtained starting terrain vertices, according to the information, the location of the terrain data may be obtained in a quadtree;

(2) 根据上述的地形位置索引四叉树; (2) According to the quadtree topographic location index;

(3) 更新局部地形数据,即在地形数据绘制对象对应的顶点数组进行 (3) update the local terrain data, i.e., data in the vertex array to draw objects corresponding to the terrain

替换; replace;

(4) 重新计算法向量信息,先求出顶点所在平面的平面法向量,然后再根据平面法向量的平均求出该顶点的法向量。 (4) recalculate the normal vector information to determine the plane of the vertex normal vector of the plane, then the normal vector of the vertex plane method based on the average vector is obtained.

Claims (5)

1、逼真三维地形几何模型的实时绘制方法,其特征在于包括下列步骤:(1)地形数据预处理,简化地形数据结构;(2)采用基于传统LRU算法与基于视点兴趣相结合的方法进行文件间的实时切换的地形调度算法,完成对地形文件的实时调度;(3)基于几何的Mip Map地形网格实施生成算法,简化地形模型;(4)基于多纹理的GPU地形Bump Map渲染算法,显示地形特征;(5)基于四叉树的遍历的地形局部替换算法,实现地形数据变换;所述步骤(2)中的地形调度算法步骤如下:(A)取当前的视点位置及朝向,得到可视地形块数据;(B)根据当前地形缓存数据和可视地形块数据更新地形缓存列表,生成下一帧数据;(C)进行缓存的更新,更新步骤如下:a. 缓存中每一块数据都有一个使用次数的统计,若下一帧需要的地形快存在于缓存中,则该统计项自动加一;b. 根据当前视点和朝向和上 1, a realistic method for real-time rendering of three-dimensional terrain geometry model, comprising the steps of: (1) pre-terrain data, terrain data structure simplified; (2) files based on conventional LRU algorithm and the viewpoint based on the combination of interest terrain real-time switching between the scheduling algorithms, the complete real-time scheduling of the terrain file; (3) Mip Map generation algorithm embodiment terrain mesh geometry, simplified terrain model; (4) a multi-GPU texture Bump Map terrain rendering algorithm, display terrain features; (5) a partial replacement topographic quadtree traversal algorithm, terrain data conversion; said step (2) scheduling algorithm terrain following steps: (a) take the current viewpoint position and orientation, to give visual topographic data blocks; (B) according to the current topography data cache block data updates and visual topographic terrain cache list, generating a next frame of data; updating cache (C), update is as follows: a piece of data for each cache. has a number of usage statistics, if a next frame exists in the required terrain faster cache, the corresponding entry is incremented by one; and B on the current view orientation and in accordance with. 一帧的试点和朝向进行比较,得出下一帧指向的数据,若该数据存在于缓存中,则统计项自动加一;c. 在此基础上,将需要但不存在的数据添加到缓存中,并将同样数量的数据从当前缓存中剔出,原则是选择当前缓存中统计项最小的数据,但不能使本次命中的;d. 若剔出的数据少于增加的数据,即缓存太小,则增加缓存数量;e. 若没有要剔出的数据,则每一帧自动将当前缓存中的统计项最小的数据块剔出,并将当前缓存大小减一,一次保持缓存不会无限制增加;f. 若系统继续工作,则返回重复c,否则终止。 A pilot orientation and for comparison, the data points to the next frame, if the data exists in the cache, then a statistical item automatic;. C is added on this basis, but will need to cache data does not exist , and the same amount of data from the current buffer excised in principle to choose a minimum data items currently in the cache statistics, but this can not hit;. d excised if data is less than the increased data, i.e. buffer it is too small, increasing the cache; E if there is no data to be excised, the statistics for each frame automatically blocks the current minimum data item cache excised, and a Save current cache size, the cache is not a holding. unlimited increase; f if the system continues to work, then return to repeat c, otherwise terminated.
2、 根据权利要求1所述的逼真三维地形几何模型的实时绘制方法,其特征在于:所述步骤(1)中的地形数据预处理的步骤如下: (1) 对原始文件数据文件分割;(2) 将分割后的文件重排,将分割后的文件組按照地理信息重新命名, 并保存在文件系统中。 2. The method of claim 1, real-time rendering realistic three-dimensional terrain model of the geometry of the preceding claims, characterized in that: the step of said terrain data in step (1) is pretreated as follows: (1) dividing the original document data file; ( 2) the rearrangement of the divided file, the file will be divided according to the geographic information group renamed and stored in the file system.
3、 根据权利要求1所述的逼真三维地形几何模型的实时绘制方法,其特征在于:所述的步骤(3)基于几何的MipMap地形网格实时生成算法步骤如下:(1 )对于新加入的地形块,将数据组成四叉树结构,统计每一地形片顶点中的参数;(2) 根据当前视点和地形块包围球中心的距离,采用适合于该精度级别的四叉树数据;(3) 根据相邻的地形片数据精度级,生成地形三角形条带,消除T型突起;(4) 将三角形条带输入到GPU,进行平滑处理。 3. The method of claim 1, real-time rendering realistic three-dimensional terrain model of the geometry of the preceding claims, characterized in that: said step (3) based on real-time generation algorithm steps MipMap terrain mesh geometry: (1) For the newcomers terrain blocks, the quad-tree structure composed of data, statistical parameters of each terrain patch vertices; (2) according to the distance and terrain blocks surrounding the current view of the center of the sphere, is adapted to the level of precision using quadtree data; (3 ) from neighboring slice data precision level terrain, terrain generating triangle strips, eliminating T-shaped protrusion; (4) the triangle strip input to the GPU, the smoothing process.
4、 根据权利要求1所述的逼真三维地形几何模型的实时绘制方法,其特征在于:所述的步骤(4)基于多紋理的GPU地形Bump Map渲染算法步骤如下:(1 )根据地形块数据生成凹凸贴图的向量图和地表地貌图;(2) 计算地表平面法向量;(3) 根据顶点数据所在平面法向量计算顶点的法向量;(4) 将法向量存储在文件中作为本算法的凹凸贴图法向紋理输入;(5) 根据地形顶点的高度,计算该定点使用地表紋理的权值;(6) 利用GPU的像素处理单元Pixel Shader合成紋理并计算光照;(7) 进行bump贴图算法。 4. The method of claim 1, real-time rendering realistic three-dimensional terrain model of the geometry of the preceding claims, characterized in that: said step (4) based GPU rendering algorithm steps Bump Map Terrain multiple textures following: (1) block of data according to the terrain generating bump mapping vector graphics and surface topography map; (2) calculation of surface plane normal vector; (3) according to the vertex data of the plane normal vector calculation vectors at the vertices; (4) the normal vector is stored in a file as the algorithm bump mapping method to a texture input; (5) the elevation of the terrain vertices calculated value of this point using the surface texture; using a GPU (6) of the pixel processing unit pixel Shader synthesized texture and lighting calculations; (7) bump mapping algorithm .
5、 根据权利要求1所述的逼真三维地形几何模型的实时绘制方法,其特征在于:所述的基于四叉树的遍历的地形局部替换算法步骤如下:(1)获取待替换地形地理位置; (2) 根据上述的地形位置索引四叉树;(3) 更新局部地形数据;(4) 重新计算法向量信息。 5. The method of claim 1, real-time rendering realistic three-dimensional terrain model of the geometry of the preceding claims, characterized in that: Topographic quadtree traversal partial replacement algorithm steps described below: (1) obtaining geographic terrain to be replaced; (2) according to the topographic location index quadtree; (3) updating the local terrain data; (4) recalculate the normal vector information.
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