日光温室环境建模和可视化技术研究

【作者】 魏伟；

【导师】 赵春江；

【作者基本信息】 首都师范大学 ， 计算机应用技术， 2009， 硕士

【摘要】 随着计算机和信息技术的发展,基于计算机的仿真和虚拟设计技术被引入到农业领域,并引起了越来越多研究人员的关注。温室是设施农业的重要组成部分,而设施农业是我国现代农业发展的主要方向。目前对温室的模拟大都以数值模拟为主,模拟结果大部分以数字和二维的形式表示出来,针对温室环境的三维建模及虚拟温室的可视化计算的研究还很少。本文围绕着日光温室三维形态的交互设计及可视化仿真应用,开展了如下工作:1.日光温室三维形态建模和交互式设计研究提出了日光温室三维结构的参数化模型,开发了交互式日光温室三维建模软件系统。该系统利用三视图设计方法得到日光温室模型的参数,根据参数生成温室的三维模型,最后在三维空间中显示设计好的日光温室模型。用户可以选择将系统提供的门、窗和风机等温室附属组件嵌入到温室模型中,组件在三维空间中的位置可以在二维视图中进行交互的调整。系统同时提供了模型导出功能,为三维日光温室模型的快速产生和重复性利用提供了便利。2.视点依赖的虚拟温室场景绘制与交互式漫游为对包含日光温室群体的虚拟农业场景进行实时、逼真的绘制,采用基于视点的连续LOD来减少实际需要绘制的网格数据量,并基于包围盒技术实现了视点的碰撞检测,同时使用可见性剔除算法来加速场景渲染速度。在渲染温室植物时,通过几何变换实现了大规模植物群体的快速构建,并在场景中使用阴影体算法来渲染阴影,生成了具有真实感的大规模虚拟温室农业场景。模拟结果表明该方法能有效地减少渲染的面元数目,大大提高了绘制速率,场景有较高的真实感,能够满足虚拟场景交互式实时漫游的要求。3.虚拟场景下雪和积雪的实时模拟提出了一种下雪和积雪过程模拟的方法,该方法采用粒子系统对雪粒子建模来模拟下雪过程,同时加入了风吹的效果;在模拟积雪时,通过在地面和屋顶构造一层三角形网格来保存雪的堆积信息,避免了保存雪粒子作为积雪实体的内存开销,同时考虑了雪飘落过程中与温室墙壁的碰撞检测;而在渲染时,采用了平均法向量和混合顶点颜色的方法来获得平滑的效果。模拟结果表明,该方法能有效地再现农业场景中下雪和积雪场景,在满足实时交互漫游的前提下表现出较强的真实感。4.日光温室采光量实时计算及可视化研究基于光的直线传播原理实时模拟了太阳光线在温室地面的投射情况,并且建立了日光温室地面太阳直接辐射计算模型和可视化方法。该方法为在虚拟温室内进行植物生长模拟提供了必要的可视化技术,此外还可以与散射辐射的模拟相结合,为日光温室内总辐射分布的模型建立和实施提供基础参数,在日光温室的采光量设计及各种植物的种植和生长模拟等研究方面具有重要的应用价值。更多还原

【Abstract】 With the rapid development of computer and information technology,computer-based simulation and design have been used extensively to the field of agricultural research,and more and more researchers have been attracted.Greenhouse is an important part of facilities agriculture,whereas facilities agriculture one of core industries in the development of agriculture in China.However,currently simulations of greenhouse are generally numerical,with figures or two-dimension results.Researches of simulating vividly the greenhouse’s internal scene and modeling greenhouse’s environment in three-dimension are less developed.The paper tries to provide methods and software for modeling virtual solar greenhouse environment.The main contents and contributions of this thesis can be listed as follows:Ⅰ.Modeling three-dimension solar greenhouse and designing interactivelyA parametedzed 3D model of solar greenhouse is proposed,and an interactive design software system for solar greenhouse is developed.The system obtains the parameters of 3D solar greenhouse by using three-view design method,and reconstructs the 3D model of a greenhouse from these parameters.The system also provide several affiliate models of greenhouse,the user can select these affiliate models for embedding them into the greenhouse model,the 3D position for placing the selected affiliate model can be translated by adjusting the corresponding position in the 2D view.Ⅱ.View-dependent model virtual greenhouse scene and interactive walkthroughA method for real-time and realistic rendering virtual agricultural scenes which include group of solar greenhouse is proposed in this paper.This method uses view-dependent continuous LOD models to reduce the amount of polygons needed to be rendered actually,and a collision detection algorithm is implemented based on bounding box.The rendering speed of the scene is improved by using visibility culling techniques.In the constructed virtual agricultural scenes, large-scale plants stands are created rapidly,by using geometric transformation,while shadow volume algorithm is implemented to render shadow in the scene.These improved significantly the realism of the virtual agricultural scene.The simulation results demonstrate the proposed method can reduce the number of rendered elements effectively,and improves the rendering speed with highly realism.This can meet the needs for real-time and interactive walkthrough in large scale virtual scenes.Ⅲ.Real-time simulation of snow falling and accumulation in virtual sceneA method is presented in this paper to simulate snow falling and accumulation,the algorithm simulates the snow falling process and models snowflake particles based on analyzing particle system,with the effects of wind-blown snow;in the simulation of snow accumulation,a blanket of triangulation mesh are constructed to store information about snow depth on the ground and roof,the memory cost for storing snowflake particles as snow accumulation therefore is avoided, the collision detection between snowflakes and the wall of greenhouse is considered in the falling process at the same time;a method of averaging normal and blending the color of vertex is adopted to obtain the smooth effect in snow rendering.The simulation results have proved that the proposed method is more effective for simulating snow falling and accumulation in agricultural scene,and it can satisfy basic need for real-time interactive navigation with realistic effects.Ⅳ.Real-time calculation and visualization of solar radiation in sunlight greenhouse Day lighting performance of a sunlight greenhouse is not only an important factor for growth and development of crops in it,but also a foundation of structural design for the sunlight greenhouse.A mathematical model of day lighting performance of a sunlight greenhouse is proposed in this paper.The change of the solar radiation in sunlight greenhouse is simulated by using 3D visualization techniques in real-time,and the change of the scope of day lighting and the solar radiation in real time can be observed visually as well.This may provide a direct method for studying and analyzing the day lighting performance and solar radiation in solar greenhouse,and help for correctly designing high-output,high-efficiency and economic sunlight greenhouse.更多还原