Street and Crossing Shapes

Default Start Rules

Street and intersection shapes generated within the CityEngine consist of different shape types. Each shape type is defined by its start rule.

Standard start rules are: Street, Sidewalk, Crossing, Junction, Freeway, FreewayEntry, Roundabout, RoundaboutIsland, and Joint.

The shape types are illustrated in the following figure.

An example street network (above), and default shape types (below).

Color Shape start rule Created by
Street Street
Sidewalk Street, and all intersection types
Joint Intersections with only 2 adjacent streets
Crossing Crossing or Smart intersections
Junction Junction or Smart intersections
Freeway Freeway or Smart intersections
FreewayEntry Freeway or Smart intersections
Roundabout Roundabout or Smart intersections
RoundaboutIsland Roundabout or Smart intersections

Note: Shapes have by default no rule file assigned. Therefore, if you like to work with these default start rules you have to define the CGA rules "Street", "Sidewalk", "Crossing", "Junction", "Freeway", "FreewayEntry", "Roundabout", "RoundaboutIsland", and "Joint". These rules will be the starting point for geometry generation.

Street Shape UV Values

For details of the UV coordiantes, see Street and Intersection Shape UVs.

Reset Shape Attributes

Since start rules can be overridden, users may want to use the Reset Shape Attributes tool to revert the start rules to the default values. To execute the tool, select a set of shapes and then choose Graph→Reset Shape Attributes from the main menu.


Because the internal shape creation algorithm computes the intersection shapes for each node individually, conflicts can occur. Usually, conflicts occur when the distance between two nodes is very small. In this case, at least one node is located inside the shape of a neighbor node.

Conflicting segments are marked with a red dashed line. The error color can be changed in the Viewport Preferences.

There is a conflict (red dashed line) because a street node is inside a crossing.

The conflict has been resolved by running the Graph Cleanup Tool.

To resolve conflicts, different actions can help: Which action to choose depends on the required level of control. It's a tradeoff between automation and quality of the result.

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