Attributes, Sources and Connections
Attributes and Parameters
Depending on their type, CityEngine scene objects can have a varying set of attributes, used for operations on the object. As an example, a node object has a set of Intersection Parameters that control the creation of its crossing shapes.
Attribute Sources and Display
These attributes can have different sources, which allows connecting the values of the attributes in various ways. Sources can be of the types
The easiest way to create connections and set sources is using the Connection Editor.
The algorithm-specific default value is used, marked with (Default). In case of rule attributes, the default value is marked with (Rule), stating that the default value is defined by the initial value of the attribute in the rule file.
The value is taken from the corresponding object attribute. The value is displayed in italic, and marked with (Object).
A rule attribute can use a shape source to take its value from the parent shape. For example a street shape may sample the street segment's streetWidth. The value is displayed in italic, and marked with (Shape).
A value that is entered by the user. It is displayed in bold. As soon as the user sets a value (or uses a slider) in the Inspector, the value changes to user source.
The value is connected to a layer, or to be more exact, to a layer attribute. The value is displayed in italic, and marked with the source layer in brackets. See Layer Attributes for details.
Whenever you enter a value to a parameter or attribute, it will automatically change to user source.
Example street parameters
|streetWidth||connected to layer Streetnetwork|
|streetOffset||user specified value|
|sidewalkWidthLeft||connected to object attribute (below)|
|sidewalkWidthRight||connected to layer Meshes|
|laneWidth||user specified value|
Example Rule attributes
Mapping Object Array Attributes to Rule Attributes
Since CGA does not support arrays, object attributes of array types are converted to string lists and mapped to rule attributes of type string.
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