3D树木建模技术研究进展

3D树木建模一直都是计算机图形学、计算机视觉、虚拟现实等领域最具有挑战性的研究方向之一，国外学者在该领域做了大量研究工作，但3D树木建模综述性文章的缺乏成为其发展的制约因素。侧重从计算机视觉的角度，将当前国内外经典的3D树木建模方法分为基于图像，基于规则和基于草图等三类，并跟踪了最新的3D树木建模技术进展，对他们的成果进行了深入剖析，重点阐述3D树木建模关键技术。最后，分析和比较了几种主要的3D树木建模技术，提出轻量化3D树木建模技术是今后虚拟场景中的交互应用的发展趋势。此外，根据当前研究的难点提出了基于单张图像的轻量化混合建模的研究思路。

Survey on virtual 3D tree modeling technologies

Realistic and immersive 3D tree modeling is one of important and challenging research topics in computer graphics, computer vision and virtual reality. Also, it is highly valuable in various applications such as virtual tourism, virtual city, virtual agriculture, ecological landscape and so on. Many researchers domestic and overseas in this field have constructed various approaches of 3D tree modeling. However, review work is not available on this topic recently, which has obviously blocked the development of image based modeling research. Different methods are classified and analyzed based on the visual clues used in modeling from a computer vision perspective. In this paper, all advanced 3D tree modeling technologies are surveyed, which are categorized as image-based, rule-based, and sketch-based methods. After analyzing and comparing several main 3D modeling and newly key modeling technologies, Such as Approximate image-based tree-modeling using particle flows, Single Image Tree Modeling, Sketch-based tree modeling using Markov random field, Texture-lobes for tree modeling, Image-based Lightweight Tree Modeling, we draw several conclusions. Rule-based tree modeling is based on the assumption that the branch shapes and phyllotaxis of the tree follow a predictable pattern, but it is difficulty to reconstruct the unpredictable part of branches such as stunted growth or suffered external environment influence. Therefore people should master large professional knowledge of botany to reconstruct realistic rule-based tree model. When it comes to sketch-based tree modeling, the users usually stretch the outline from the tree images to obtain the seeds, which guide the growth of trees or morphological characteristics. Tree modeling is relatively simple and intuitive and even can be realized by automatic or semi-automatic way. Image-based tree modeling is a method that 3D space geometry information of the tree is built from two or more than two images. It can be built intelligently and the model is realistic. But the model data is too large to meet 3D visualization display of the large-scale virtual scene on the Internet. In addition, a research idea about hybrid lightweight tree modeling for lightweight, low cost, high efficiency, which is proposed according to the current research emphasis and difficulties. At last, the future of lightweight 3D tree modeling applied in the interactive virtual scene is presented.