L-系统的基本概念和示例

L－系统（L-system）是表达植物形态结构和生长规则的重要方法,因而是设计虚拟植物,模拟植物生长发育过程和农作物育种的重要工具,本文力求深入浅出而又不失严谨地介绍L－系统的基本概念,分类和典型示例,希望通过本文能引起广大农业科研工作者对L－系统的兴趣。

Essential Concept of L-system and Examples

In this paper,we will look at the basic definitions of L system,types of L systems(context free L system,context sensitive L systems,stochastic L system,deterministic L systems and D0L system),turtle graphics and some examples.L systems are very useful for generating realistic plant structures.The concept of an L system,developed in 1968 by Aristid Lindenmayer,soon came to be recognized as a mechanism for modeling various plant like structures.An L system is a scheme for rewriting strings of symbols.The rewriting takes place by replacing certain strings of characters in a word by other strings of characters.These replacements often utilize repetitions of the string of characters being replaced,and so complex strings are built up from simple strings,the complex strings containing replications of the basic strings.To give geometric life to a string of characters,we interpret a character string as a sequence of geometric drawing instructions using a scheme that is commonly referred to as "turtle graphics":the geometric object is formed out of the trail left by a "turtle"that follows very specific but brief motions.We believe L system will be a new interest to researchers,teachers and students working in agriculture.