摘要
随着虚拟现实技术和计算机图形学的发展,利用计算机虚拟现实世界成为热门课题。而种类繁多的植物是构成自然景物的基础,因此,虚拟植物成为当今计算机图形学领域的研究热点之一。由于植物结构复杂、形态多样,使得图形学技术在该领域面临许多挑战,并随着计算机软硬件处理海量数据能力的提高,呈现两个主要的发展趋势：是宏观方向的发展,表现为范围大、复杂度高的场景实时绘制,涵盖海量数据的存储、优化；另一个重要趋势是微观方向的发展,表现为构建的虚拟植物的模型尺度的加细,从单个植株逐渐深入到植物器官或更小尺度的几何造型,应用于精确模拟植物的真实生理过程。本文从微观角度出发,对植物精细建模概念进行详细阐述,将烟草作为主要的研究对象,就如何构建精细的植物器官模型、实现从器官到植株的可视化模拟进行了探讨。
为实现植物器官的精细建模与可视化,本文以烟草为例,提出了基于结构骨架和参数的器官交互式建模方法,对烟草叶片、花朵进行细节模拟。在叶片建模过程中,通过分析烟草叶片的形态结构,将脉序作为结构骨架,利用三维数字化仪获取烟草叶片脉序和边缘主要形态特征点,综合球B样条曲线和插值样条曲面实现了烟草叶片的三维重建和真实感显示。在花朵建模方面,针对烟草单花花冠联合的特点,提出了基于球B样条曲线和参数曲面的单花建模方法,提取了模型控制参数,实现了多个开花状态的仿真；针对烟草花序为聚散花序的特点,提出了一种基于分形系统的植物花序可视化仿真方法,通过构造初始分形单元,以仿射变换为基本框架,按照一定的迭代生成算法,建立了烟草花序结构与几何模型,实现了花序生长模拟。最后,根据整个植株的拓扑结构,完成植株模型的初步建立。可视化结果表明,该方法建立各模型都有较高的真实感,为农学研究者提供便捷的烟草可视化研究平台。
As development of virtual reality technology and computer graphics, the use of computers in the virtual reality becomes hot topics. Various species of plant is foundation of natural scene, therefore, virtual plant becomes one of key researches in computer graphics fields nowadays. With complex structures and various forms of plant, graphics in the field faced many challenges, and as capability of data processing of computer software or hardware is improving, there are two main trends:one is broad direction which focus on real-time rendering of complicated scene, covers storage and optimization of mass data; another trend is microcosmic modeling in which scale is from a single plant to organs even smaller particles, aims at simulation of plant actual physical process. From the micro perspective, this paper describes the concept of fine modeling in details, taking tobacco as an example, explores how to build fine models of organs and realize visualization of organs to single plant.
In order to realize explicit modeling and visualization of plant organs, taking tobacco plant as an example, an interactive modeling method based on skeleton structure and parameters is proposed in this paper, which generates the detail model render of leaves and flowers. In leaf modeling, through analysis of morphological structure of tobacco leaves,3D scanner is used to get principal characteristic points of their veins and fringe, and then ball B-spline curve and B-spline surface are combined used to realize 3D reconstruction and reality exhibition of them. In tobacco flowers modeling, for the feature of crown united, we propose a flower modeling method based on ball B-spline curve and parametric surface, and get the control parameters to realize simulation of several model in different flowering states; for the characteristic of group inflorescence, we propose a visualized simulation method for plant inflorescence based on fractal system. Through establishment of initial fractal unit, with affine transformation as the basic framework, the geometrical and structural growth model of tobacco inflorescence are constructed, according to a certain iterative generation algorithm, what is more, the growth process is completed, that provides a new technical means for other similar flowers modeling. Finally, tobacco complete plant model are preliminary established according to its topological structure. The visual results show that all model have more reality, that provide convenient visual platform for agricultural researchers.
引文
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