Intersection Parameters

Intersection Parameters can be individually set for each graph node.

The parameters for Intersection Shape creation can be specified through the intersection parameter panel in the inspector.

Parameter panel for intersection shape creation

Several parameters are available for the user to control the resulting intersection shapes. Intersection parameters define the type of the intersection (crossing, junction, roundabout, freeway or smart) and specify geometry details like the radius of the arcs for instance.

Attributes can be mapped to Default, User, Object or to a map layer. See Mapping Attributes for details.

General Parameters

Parameter Function
shapeCreation If true, shapes are created from the graph node.
type Specifies the type of the intersection. Crossing, junction, roundabout or freeway. Smart automatically chooses between these types.





Common Parameters

Parameter Function
precision Specifies the level of detail.

Value must be in the range [0, 1].

Crossing shapes with precision = 0.1.

Crossing shapes with precision = 0.3.

minArcRadius The minimal arc radius. For freeways a higher value (>20) is better suited.

Given in absolute length units.

Crossing shapes with minArcRadius = 0.

Crossing shapes with minArcRadius = 5.

angleThreshold Minimum angle between streets before they automatically start bending to avoid each other. It is ignored for freeways.

Crossing with angleThreshold set to 30. Note the streets bending to avoid each other.

Crossing with angleThreshold set to 10.

Crossing and Junction Parameters

In addition to the above parameters, crossing and junction creation have a:
Parameter Function
cornerStyle Either Arcs or Straight. When set to the latter, blocks get simpler.

Border with cornerStyle set to Arcs.

Border with cornerStyle set to Straight.

Roundabout Parameters

In addition to the general parameters, roundabout creation uses the following values:

Additional parameters for roundabout creation

Parameter Function
innerRadius Defines the radius of the inner circle (the "island shape").
streetWidth Defines the width of the roundabout street lane.

A roundabout with innerRadius = 5 and streetWidth = 10.

A roundabout with innerRadius = 10 and streetWidth = 5.

Both values are given in absolute length units.

Principle Street Selection

The junction and freeway intersection types make use of the principle street to determine the intersection geometry. The principle street does not alter the smart junction behaviour.

Left: Two junctions with different principle streets. Right: Two freeway intersections with different principle streets. In each case the principle streets are drawn in a darker shade of grey.

The principle street is specified using either the street tool, or by setting the object attribute principleStreetStart or principleStreetEnd on adjacent streets as appropriate.


Simple curve

Valence-two nodes (nodes between 2 graph segments) usually lead to curves or links between the segments.

A simple curve.

For valence-one (nodes at the end of a row of segments / cul-de-sac)or valence-two nodes it does not matter whether the type is crossing or junction.

Dead end street

By setting the type of a valence-one node to roundabout, one can model a cul-de-sac.

A cul-de-sac.


Junctions, as opposed to crossings, don't break a major street. Minor streets are connected to the major street by junction entries.

A simple junction with two junction entries (left and right).

The two segments with the maximal street widths are automatically treated as major street.

Auto-generated connection attributes

Connection attributes provide basic information about the underlying graph and give context information. CGA rules may want to access the following attributes.
Parameter Value
valency The number of street segments adjacent to a street node. Valency is added to all intersection shapes.
sidewalkSide Which side of the street this Sidewalk shape is on, relative to the street direction: either Left or Right. SidewalkSide is only added to Sidewalk shapes.

Connection attributes are object attributes of the graph node and are inherited to the shape. Note the italic font in the shape's inspector.

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