Script-based export—ArcGIS CityEngine Resources

Another powerful feature of the scripting interface is the Script Based Export. Arbitrary python commands can be executed during model generation via callback methods.

Script-based export template

Create a new python export script from template File > New... > Python > Python Module
Choose Module: Export (Reporting) as template

Creating a new Python module from the export template

Export callback functions

When a new module is created from the export template, the following callback methods are present:


initExport	Called before the export starts
initModel	Called for each shape before generation.
finishModel	Called for each shape after generation.
finishExport	Called after all shapes are generated.

Such a script can be used for

the Script based Export (Python)
This "exporter" generates the models and executes the attached python script in parallel. No geometry files are created.
Any geometry exporter
The models are generated and exported as usual, the attached python script is executed in parallel.

OBJ export dialog with script set in Misc options

Example : Processing CGA report data

The following code snippet is a typical example of a CGA rule that reports data during generation.

FloorArea --> report("area", geometry.area)

Reported data can be accessed using the export callback functions.

The code below gives an example of how report data can be accessed and written to a file.

'''
Created on Nov 6, 2013

@author: andi
'''
from scripting import *

# Get a CityEngine instance
ce = CE()

REPORT = ""

def initExport(exportContextOID):
    global REPORT
    REPORT = "Name,#Floors,totalFloorArea,averageFloorArea\n"

def finishModel(exportContextOID, shapeOID, modelOID):
    shape = Shape(shapeOID)
    model = Model(modelOID)

    global REPORT
    i = 0
    totalArea = 0.0
    reports = model.getReports()
    if 'area' in reports.keys():
        for area in reports['floorArea']:
            totalArea +=area
            i+=1
        REPORT += "%s,%d,%f,%f\n" % (ce.getName(shape), i, area, area/i)
    else :
        REPORT += "%s,%d,%f,%f\n" % (model, 0, 0, 0)

def finishExport(exportContextOID):
    filename = ce.toFSPath("models/"+"/reportdata.txt")
    FILE = open(filename, "w")
    FILE.write(REPORT)
    FILE.close()

In this case, the resulting comma-separated file contains the following data:


Name	#Floors	totalFloorArea	avgFloorArea
LotSouth_35	5	357.3825	71.47651
LotSouth_37	4	335.8072	83.95179
LotSouth_38	3	379.4594	126.4865
...	...	...	...

Specific methods in callback functions

These Python methods only work in callback functions


method	description
model.getReports()	returns dict of CGA report() data
model.getOffsets()	returns tuple of local/global export offsets

Checking Module Name

To prevent code outside the callback methods from being executed when the exporter calls the script, the module attribute __name__ can be used to distinguish the caller.

if __name__ == '__main__':
    #only do stuff is script is started directly

This allows to have a script that can both be used for normal Python exection as well as for script-based export, e.g.

def finishModel(exportContextOID, shapeOID, modelOID):
    # export callback code

if __name__ == '__main__':
    exportSettings = OBJExportModelSettings()
    exportSettings.setScript("/general/scripts/scriptbasedexport.py")
    ce.export(ce.selection(), exportSettings)

In the example above the main clause will not be executed when the script is called by the script-based exporter

Module names in different contexts

Resulting module name __name__ in different contexts:


Context	Module Name
context is being run by itself	__main__
context is started from exporter	__export__
context is started on startup procedure	__startup__