【作者】 刘艳慧；

【导师】 谢宝元；

【作者基本信息】 北京林业大学 ， 工程绿化， 2008， 博士

【摘要】 本文以景观元素地形、植物、水体为研究对象,运用计算机图形学中三维模型的有关原理对其进行了建模及其应用研究,主要目的在于为景观规划、农林业研究及经营管理和三维表达提供必要的、高精度的模型基础,进而建立数字景观、数字农林业等现代技术系统,促进农林业和景观领域的可持续发展。本文选择了利于建模、功能强大、使用范围广的3ds max作为三维表达的软件平台,研究了地形、植物、水体三维建模的一般方法。其中,地形建模主要讨论了Extrude法、Terrain法、灰度图置换法、Patch Grid法、随机生成法和软件生成法;植物建模主要讨论了十字树法、剪影法、层状树冠法、几何参数实体、基于圆柱体的手工实体模型、混合式模型、程序式三维植物模型和软件生成法,并着重运用分形理论中L-系统方法对植物进行建模,本文以油松为例,通过对油松树干高度、树枝长度、分枝点和分枝角度的调查,分析了它们之间的比例关系,并基于L-系统理论,采用VB编程计算坐标,模拟单株植物的三维模型,并通过模型的理论研究讨论了其在实际中的应用;水体建模主要讨论了表面模型、表面波纹、实体模型,以及运用颜色、反射、折射和透明度等技术模拟水的纹理,运用贴图法、涟漪法模拟波纹效果,运用颗粒系统模拟喷泉、雨、雪等水体运动的效果。本文着重对各景观元素的建模方法进行了比较分析,并提出了三个景观元素以及景观合成在实践中的应用,通过研究得出如下结论:1.地形建模在有精确地形图数据的情况下,可采用Terrain法、Patch Grid法和灰度图置换法。其中Terrain法是生成三维地形效果最好、最精确、最直观的方法,Patch Grid法次之,灰度图置换法由于灰度图在应用中较难处理,故生成的三维地形与实际地形有一定差距。对于不要求精确地形,只是作为中远景或配景的地形来说,可用灰度图置换法、Patch Grid法和随机生成法生成。其中随机生成法生成的地形效果最自然,方法也较简单;灰度图置换法次之,Patch Grid法由于要手动控制点层级的各项修改,故生成的地形没有前两种方法简单方便,但是对于要求地形轮廓,又在无地形数据的情况下,就只能采用Patch Grid法,它可随意调控出要求的地形形状。2.植物建模通过对十字树法、几何参数模型法、软件直接生成模型法(3ds max软件和Tree strom插件)、二维贴图法进行对比分析得出Tree storm法生成的植物模型是最优的,其它依次是二维贴图法、3ds max法、十字树法、几何参数模型法。从中可以看出Tree storm和二维贴图法制作的植物效果好,也较易操作,但是Tree storm生成的是纯三维模型,更易观察、透视感强。但是随着树木模型的增加,Tree storm的运行速度会很慢,因此在纯三维的模型制作中,可以采用Tree storm+十字树法生成,近景树木用Tree storm生成,中远景用十字树法来完成,这样制作的模型,即可满足良好的三维效果、透视效果和真实感,还解决了运行速度慢的缺点。3.水体建模常用表面模型来表现,因为它易于操控,可以在它上面进行变形、贴图等操作;而实体模型一般只用来表现水滴等变形实体。模拟水体波纹常用贴图法和涟漪法,方法简单,模拟波纹效果很好,在设计中使用率较高;而制作喷泉、瀑布、雨雪等景观效果的最好方法就是粒子系统。粒子系统一般常用来表现水的动态效果,而在表现静态景观效果时,常用photoshop贴图法来代替三维模型,可以节省时间,而且可能更有真实感。4.通过景观规划设计实例,得出景观合成的可操作方法。三种景观合成方法,根据设计要求,可灵活使用。建议在做小场景的景观规划设计时,尽量采用纯三维模型景观合成方法,还可制作动画效果;在制作较大场景的景观规划设计时,制作纯三维模型耗费时间太多,占用内存过大,而二维模型在大场景制作时又要进行大量的透视、阴影处理等,建议不采用这两种方法,可采用三维模型+二维模型的景观合成方法,选择合理的地形、植物、水体建模方法,在三维软件中选择一个合适的视点进行渲染,再在图形软件中进行后期处理。5.基于L-系统理论模拟得到的三维模型具有一定的逼真性,并且可以用于实践中。另外,该模型的分枝结构计算是采用VB编程实现的,VB的高效性和灵活性使模型的后期改进和扩展成为可能。将L-理论用于三维构建的研究和实践,对其它物质的三维构建有一定的借鉴作用。本文主要创新点有以下两个方面:1.在对景观元素地形、植物、水体的建模方法讨论的基础上,提出了各景观元素和景观合成在实际应用的可操作方法,对今后的学习和工作具有借鉴和指导意义;2.提出了基于L-系统理论的植物建模方法,把植物在生理特性和形态结构有机的结合起来,建立真实的植物模型。更多还原

【Abstract】 This text takes some landscape factors such as terrain, plant and water as research objects. Based on the principle of Computer Graphics. The purpose is providing necessary and exact modeling basic for landscape programming, agriculture and forest research and 3D expression. Moreover, it can enrich the technology of Digital Landscape and Digital Agriculture, take them a continuance development.This paper chose to modeling, powerful, the use of a wide range of 3ds max as a three-dimensional expression of the software platform to study the topography, vegetation, water body three-dimensional modeling of the general approach. The terrain modeling discussed the Extrude、method of Terrain,method of grey plan Displace ,method of Patch Grid, method of random creation and method of software creation. The 3D modelling of plant talk over method of cross tree, method of silhouette, method of samdwich crown, Geometric parameter trees,plant model made by cylinders, Composite plant model, programmable three dimensional model of plant and model of software creation, and stresses the use of fractal theory of L-systems approach to modeling plant .This article take the Chinese pine as an example, establishes mathematics equation of the plant growth through the determination to the Chinese pine bough length, the branch length, the winding point, the branching angle and proportionality factor’s. Utilizes the L- system theory, uses the VB programming, simulates the three-dimensional model to the single plant, and discussed its application in reality through the model research. The 3D modelling of water debated water surface model,surface corrugation and solid model, and applyied the technique of water color, water transparency,reflection, refraction etc to simulate water’s vein, utilized the method of plastering picture and ripple to simulate corrugation effection, used particle system to simulate the effect of water moving to fountain, rain, snow and so on.This article emphatically has carried on the comparative analysis to the various landscapes element’s modeling methods, and proposed three landscape elements as well as the landscape synthesis applied research in reality, then draws the following conclusions:1. Terrain modeling can use method of Terrain , grey plan Displace and Patch Grid method in the case of having a precise topographic map data. Terrain which is generated three-dimensional topography of the best, most accurate, most intuitive approach, Patch Grid of times. Grey plan is more difficult to handle in the application so there are some certain gap between the actual terrain and three-dimensional topography by method of grey plan Displace. The terrain does not require precise, just as the King of vision or with the terrain, can be used method of grey plan Displace ,method of Patch Grid, method of random creation . Method of random creation is the most natural effect of the topography, and this method is more simple. The method of grey plan Displace is a little worse. Patch Grid law is not more simple and convient than the two methods ahead in generating the terrain due to manual control the modified of point level. We have to use Patch Grid if there is not terrain data and the terrain contour is requested because it can easily control the requirements of the terrain shape.2.Tree storm generated by the plant model is the best through a comparative analysis to method of cross tree, geometric parameter model, the software directly Generation Model Law (3ds max software and plug-Tree storm), 2D map drawn by plant modelling. Followed by other 2D map drawn, 3ds max, method of cross tree and geometric parameter model. It can be seen the plant produced good results and easier to operate using the Tree storm and 2D map drawn. But Tree storm-generated three-dimensional model is pure, more observation, strong sense of perspective.However, Tree storm’s speed will be very slow with the increasing of the trees model.So we can use Tree storm + Cross tree in pure three-dimensional model, close-range trees with Tree storm generated and in the long-term use the cross tree. You can meet a good three-dimensional effects, effectiveness and realistic perspective, but also solved the shortcoming of the slow speed in this way.3.Surface water modeling commonly used to model performance because it easily manipulated and can carry out the deformation, textures and other operations above it though solid model is generally used to drop performance of entities, such as deformation. Utilized the method of plastering picture and ripple to simulate corrugation effection is more simple and better effect of simulated ripple so it has a high utilization rate in the design. The best way to produce the landscape effects of fountains , falls, rain and snow is particle system. Particle systems are generally used to water the dynamic performance effects and 2D textures commonly be used to replace the three-dimensional model method.You can save time and maybe have more sense of reality.4. We can draw the operational methods of landscape through landscape planning and design examples. Three landscape synthesis methods can be used flexibly in accordance with design requirements. You may use three-dimensional model of purely visual synthesis methods in small scenes of landscape planning design and can create animation. When we produce large landscape planning design, it will take up too much time and memory to make pure three-dimensional model while the two-dimensional model will use a lot of perspective, the shadow processing in large scene production so we do not advice to use them. We can use the landscape synthesis methods of three-dimensional model + two-dimensional model and choose the reasonable topography, vegetation, water modeling, then select a suitable view to rendering in the three-dimensional software and graphics software in a post-processing. 5.Three-dimensional model based on the L-system theory of simulated has a realistic and can be used in practice. In addition, the model is the programming with VB and the efficiency and flexibility of VB make it is possible to improve and expand the latter part of the model. The research and practice of L-theory used to construct three-dimensional will be reference to other materials three-dimensional construction.6. The 3ds max software has powerful features, a rich modeling tool, the top rendering and animation capabilities in the application. Topography, vegetation and water landscape elements in 3ds max can be very good in the modeling and rendering, However, in order to establish good 3ds max effect of landscape, it is necessary to use 3ds max plug-in the production environment, plug-in trees, landscape plug-in, etc. In addition, we can also use other image processing software to create visual effects synthesis.There are two innovations in this text. First, based on the modeling method of terrain, plant and water, provided the maneuverable steps of landscape composing. It has important and directive significance to aftertime study and work. Second, this text provided a modeling method based on L-System, simulated plant growth, which with physiological characteristic and configuration.更多还原