How do I place street furniture like lamp poles or trees?

Answer

Note:
CGA stands for Computer Generated Architecture, a scripting language specific to Esri CityEngine and used to generate 3D content. See the link to the 'Basics of Rule-based Modeling' in the Related Information section below.

Code:
Sidewalk -->
    SidewalkShape.     # Original shape
    PutTrees    # Duplicate of the shape for placing trees

Code:
Sidewalk -->
    SidewalkGeometry.
    SidewalkObjects     # shape duplicated!

# idea : we cut off small strips of the original shape sideways and along the length of the sidewalk.
# on the remaining shape 'dots' (small rectangular shapes), we insert a post.
    
attr placementWidth = 0.05

attr streetDist = 0.2
attr objectDist = 5

attr objectSize = 0.1
attr objectHeigt = 2

SidewalkObjects -->
    # split sideways the sidewalk shape
    split(v,unitSpace,0) { streetDist : NIL | placementWidth : PlacementStrip | ~1 : NIL  }
    
    
PlacementStrip -->
    # split along the sidewalk shape
    split(u,unitSpace,0) {objectDist: NIL | placementWidth : PlacementPoint }*

PlacementPoint -->
    alignScopeToGeometry(yUp, 0) # align the shape to the current point shape, thus the street direction!
    #r(0,90,0) # toggle 90 degree rotation, e.g. for lamp poles
    s(objectSize*2, objectHeigt, objectSize)
    i("builtin:cube")
    center(xz)