What are Shapes?

Shapes are the most important entity within a CityEngine scene. They are the main input for procedural modeling with CGA rules. CGA rules operate on shapes and thus there must be some shape to apply the start rule. Through CGA operations, shapes are modified and finally result in model geometry.

Geometrically speaking, shapes are simply polygons. They can be drawn manually 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, automatically from a street graph and blocks, 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.

Shapes created manually are referred to as Static Shapes, while shapes derived from street graphs and block subdivision are called Dynamic Shapes.

Imported Shapes

Shapes from various file formats can be imported, including Esri FileGDB (.gdb), Esri Shapefiles (.shp), Wavefront OBJ (.obj), Autodesk FBX (.fbx) and OpenStreetMap (.osm). See Importing Shapes. A convenient way to import shapes is through ArcGIS Online and the Get Map Data feature.


Lots imported from a ".shp" file.

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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