Workflow 1
Export 3D procedural models from CityEngine with linked metadata and paradata.
*Before Workflow 1 can be run, a user must create a procedurally generated 3D scene and install the customized Python script in CityEngine.
Installation
Open the CityEngine Navigator pane. Download the export_to_kda.py script (Dussault 2018a) and drag it into the workspace "scripts" directory. Select "Copy files" when a dialogue box appears. The script was designed to rely on only modules available by default within the CityEngine Python environment, so no further installation steps are required.
Figure One
Scene Preparation
The script generates objects that were procedurally generated as "shapes" in CityEngine. A user can hand-draw footprints or import a shapefile. Select one or more footprints, apply CGA rules, and generate 3D models (structures). Optionally, but encouraged, apply from shapefile attributes or enter specific names for each of the structures that will be exported. Finally, select those objects that will be exported.
Export
Navigate to "File" > "Export Models…" and select "Script Based Export (Python)." Browse for export_to_kda.py.
Figure Two
When "Finish" is selected, the script will begin to execute. First, it creates a directory in the "models" directory of the current project in which it will save all the exported files. This directory is currently named after the layer of the first object, but the naming convention may need to be considered in more depth as further work is done in the future. Then, the script iterates through each of the distinct structures (considered "shapes" by CityEngine). For each object, it creates a subdirectory and creates several files inside. Finally, the script creates files for the entire group of objects, what KDA refers to as the "scene."
Output
Upon a successful run, the script will have generated a directory with a layer name, a COLLADA (.dae) file, JSON file, export log, and assets, as well as subdirectories for each object with similar contents and an additional file described later, an RPK.
Figure Three
Troubleshooting
CityEngine's Python error handling tends to silently fail instead of raising an exception. Despite the lack of obvious errors, it may be helpful to open the CityEngine console to watch the script's output. In the event that the RPK fails to be created based on improperly formed CGA rules, an error will be printed to the console and execution of the script continues. Additionally, if there is a problem with the exporter itself, CityEngine will display the exporting wizard for the user to manually navigate (Dussault 2018b).