What are Shapes

Shapes are the starting point for every CGA generation. CGA rules operate on shapes and thus there must be some shape to apply the first rule on. Through CGA operation, the shapes are modified and finally result in geometries.

Geometrically speaking, shapes are simply polygons. They can be generated within the CityEngine or imported from external sources.

Shapes can reference a set of attributes, including a rule file, a start rule (the first rule that will be applied) as well as a seed to control randomness. You can assign rules to shapes by selecting the menu Shapes -> Assign Rule File....

Shapes are created either manually by hand, automatically from a graph, or by import:

Manually Created Shapes

Shapes can be drawn and edited using a set of tools, see Creating and Editing Shapes Manually.


A simple lot drawn within CityEngine.

Shapes Created from a Graph

Street shapes and lots can be automatically created from a graph, see Creating Shapes from Graph Networks.


Street shapes and lots generated from a graph within CityEngine.

Imported Shapes

Shapes from various file formats, including ".obj", ".dxf", ".shp" and ".osm", can be imported. See Importing Shapes.


Lots imported from a ".shp" file.

Unfortunately, the term Shape is also used in the context of Rule-based Modeling, see Shapes. Please don't confuse these two types of shapes.

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