City Engine Setback understanding

Question

Can anyone point me to complete documentation on how setback operation relates to a network, beyond CityEngine help documentation?  Specifically, we're having difficulty getting correct setbacks on corner lots where road network surrounds two sides of a lot within a block.

CherylLau · Answer

Could you explain a little more about what the problem is?

Setback using street.front as the selector should work on corner lots.  All edges that are labeled as front should be part of the setback.  See the first example (Setback on Street Front) in the setback help doc for an image and code.

setback Operation

DavidWasserman · Answer

Hi Emily,

Are you having a first edge problem? You might need to manually set the first edge on some shapes if the set first edge tool does not do what you want shapes. You also will want to make sure your streets have a streetWidth attribute for some types of setbacks. 
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From the docs:

Set First Edge. This operation sets the first edge of a face to the currently selected edge. This step is often needed to orient a face's "zero" edge towards a street (e.g. for placing the buildings front correctly). If a face is selected, the highlighted gradient line indicates the first edge (with gradient from vertex 0 to vertex 1).

Set Street Edges. This operation marks selected edges as street edges. More specifically, it sets the street width object attribute array to 1 for selected edge indices. When mapped to a CGA rule, the streetWidth() attribute can be used to identify edges or faces that are facing a street. (see also comp() in CGA reference)

Compute First/Street Edges. This operation automatically calculates the first and street width attributes of the selected shapes. It works as follows: First it finds the nearest street (within 100m) for every edge of a shape. The corresponding street width attribute is set to the width of the nearest street. The edge closest to a street is set as the first edge (edge 0).
Related docs on Setback:

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Related Docs on Block Parameters:

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Do any of these seem related?

David