CityEngine-基于规则建模和输出模型

Rule-based Modeling 基 于

规则的建模

In CityEngine, building

models are described through CGA Rules. A CGA rule file consists of several rules that define how the actual building geometry is created. After a CGA rule file is assigned to a

shape, the generation of the building model starting from this shape can begin. In this tutorial we will create a single CGA file with very basic rules.

在城市引擎中，建筑模型是通过 CGA Rules

规则

进行描述的，一个 CGA 文件数个规则规则组成，他们定义了建筑按照一定的几何学生成。然后一个 CGA 被指定给

一个图形，这一代的建筑模型将会在指定的图形范围生成。在这次的实例中我将学会使用非常基本的规则语句创建一个单独的 CGA 文件。

Creating and writing a new rule file 创建和编写一个新的规则文件

这个新的 CGA 文件创建在你的工程项目中的规则目录里面，CGA 规则编辑器是打开的。

在 CGA 规则编辑器中，可以根据规定的建筑参数开始编写语法程序。因此，建筑高度的最小值和最大值定义为规则属性。这些变量能随后很方便的通过导航器来改

变单个建筑的高度。

attr minheight = 10

attr maxheight = 30

Every shape (lot or street shape) has a specific start rule that triggers a rule from the rule file. For example, lots generated in the CityEngine have the start rule Lot by default.

Select a single lot and look into the Inspector to see the current start rule.

每一个图形（地块或者街道图形）一开始有一个特定的规则文件触发器。例如：在通过预设规则文件产生的城市引擎中，拾取一个地块然后查看导航器中的初始规则。

The start rule defines the first rule

that is triggered form the rule set.