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题名:
基于图象的树木造型方法的研究
作者: 严涛
答辩日期: 2000
专业: 计算机应用技术
授予单位: 中国科学院软件研究所
授予地点: 中国科学院软件研究所
学位: 博士
关键词: 基于图象的造型 ; 植物造型 ; 基于光照的形状恢复 ; 立体视觉 ; 动态规划 ; 骨架 ; 虚拟现实
摘要: 基于图象的造型技术(Image-based modeling)是目前计算机图形学的研究热点之一。与传统的基于几何的造型技术相比,基于图象的造型技术由于具有造型过程简单直观、真实感强等许多优点,因此自九十年代中期出现后,引起了学术界的广泛关注,在短短几年内得到了迅速发展,很快便成为计算机图形学中一个有着强大生命力和应用前景的新的分支。本文基于计算机图形学、图象处理、图象变形以及计算机视觉领域的一些方法和技术,着重研究了一类复杂自然景物-树木的基于图象的造型技术。与传统的基于数学或生物学的树木造型方法不同,我们以一幅或多幅图象为输入,通过人机交互、充分分析和利用图象信息,生成形态上与图象中的自然树木极为类似的几何模型。由于取材于真实的自然树木,造型具有很强的真实感。作为对另一类复杂自然景物-火焰及云的造型的研究,我们提出了一种用于虚拟现实(VR)系统的导弹尾焰和云的实时生成算法,该方法已被应用于国家 863 计划 306 主题项目:“分布式虚拟战场环境-虚拟仿真环境关键支撑技术及应用”,收到了良好效果。本文的主要工作包括:1、提出了一种基于单幅图象的树木枝干深度估计和造型方法,根据树木的特殊结构,实现了自然光照下枝干三维形态的分析与恢复;2、提出了一种基于多幅图象的树木造型方法,在枝干抽取方面对交互式图象分割算法“智能剪刀”做了重要改进;在骨架抽取方面提出和实现了一种基于动态规划进行连通判定的骨架抽取算法;在相机定标方面实现了自然场景于平面定标物的两步法定标;在对应点匹配问题上避免了点对点的匹配,代之以更大的、具有全局性质的基元的匹配;上述工作都使造型算法的鲁棒性和实用性得到了很大的提高。3、提出了一种虚拟现实系统中导弹尾焰的实时生成算法,实时且真实地模拟了导弹的三维尾焰,并采用类似方法实现了云的实时模拟。本文共分五章,第一章对基于图象的造型技术和传统树木造型方法分别作了总结和概述,第二章叙述了基于单幅图象的树木造型方法,第三章讨论了基于多幅图象的树木造型方法,第四章给出了导弹尾焰和云的实时生成算法。最后,第五章对本文的工作作了总结,并指出了未来的工作要点和方向。
英文摘要: The technique of extracting objects' geometrical representations from images,known as image-based modeling, has received considerable attention in both fields of computer vision and computer graphics. In comparison with geometry-based modeling, image-based modeling offers an easier modeling process at a higher realistic level. Therefore, it becomes an active research area in computer graphics shortly after it was proposed in the mid-1990s. This thesis focuses on the topic of image-based modeling of trees from one or multiple images, based on a number of techniques and algorithms in the field of image processing, image morphology, computer vision, as well as computer graphics. Unlike traditional mathematical-based or botanical-based plant modeling synthesis, our method takes one or multiple images as input and extracts a geometric model from the images by analyzing image information and making good use of user's interactions. Due to the nature of image-based modeling, the result model is quite realistic. As an example of modeling another class of complex natural objects, fire and clouds, we also present a method that performs real-time simulation of rocket fire and clouds in VR applications. Impressive results have been observed when the method is employed in Cyclone'2000, a VR system of 863 National 863 Hi-Tech Project. The main contribution of this thesis includes: 1. Presentation of a single-image-based tree modeling algorithm, which managed to make use of the special structure of trees to estimate the 3D shape of every branch under natural lighting conditions. 2. Proposal of a multiple-image-based tree modeling algorithm, composed of four stages: branch segmentation, skeleton extraction, camera calibration and 3D-shape recovery. Efforts were made for the sake of acceleration and simplification in the following aspects: · An essential modification of "the Intelligent Scissors", an effective interactive segmentation algorithm presented by Mortensen and Barrett on SIGGRAPH'95. · A dynamic programming based skeleton extraction algorithm. · The implementation of a two-step, co-planar reference object based calibration algorithm in natural outdoor environment. · Utilization of branch-to-branch correspondence instead of point-to-point correspondence to enhance the robustness and simplification of the stereo matching process. 3. Presentation of a real-time rocket fire simulation algorithm for VR systems, together with a real-time cloud generation procedure. The thesis is divided into five chapters. A brief introduction to image-based modeling and traditional geometry-based plant modeling is given in Chapter 1. Chapter 2 illustrates the single-image-based tree-modeling algorithm, and Chapter 3, the main part of the thesis, discusses the multiple-image-based tree-modeling methodology in detail. Chapter 4 explains the algorithms used in real-time rocket fire simulation, together with a simple procedure for real-time cloud generation. Finally, a conclusion and some future works are addressed in Chapter 5.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.iscas.ac.cn/handle/311060/7630
Appears in Collections:中科院软件所

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Recommended Citation:
严涛. 基于图象的树木造型方法的研究[D]. 中国科学院软件研究所. 中国科学院软件研究所. 2000-01-01.
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