Selecting within a selection

Question

I have a file with land use and building footprints. I have gotten to the point in python of selecting all the land use shps from the object attributes. In this picture:

I have written code that has selected everything tagged as residential in the object attributes.

def selectByAttribute(attr, value):
    shapes = getObjectsFrom(ce.scene)
    selection = []
    for s in shapes:
        attrvalue = ce.getAttribute(s, attr)
        if attrvalue  ==  value:
            selection.append(s)

ce.setSelection(selection)

if __name__ == '__main__':
    selectByAttribute("landuse","residential")
    pass

My question then becomes, how do I select the footprints within those already selected polygons, and nothing else? This is where I have gotten stuck.

Please help? And help me like I have no coding knowledge what so ever. I have an art degree, and the above took me almost 2 days to figure out.

Thanks in advance!!!!

Monica

Edit: Essentially, I would like to "Select by Location" like I would in ArcPRO. Which, would be a nice feature to have in general.

JonasObertuefer · Answer

To follow up on this, I recorded a quick video to showcase the workflow:

Additional resources:

* Context and occlusion queries—ArcGIS CityEngine Resources | Documentation  
* inside / overlaps / touches function (occlusion queries)—ArcGIS CityEngine Resources | Documentation 
* Script-based export—ArcGIS CityEngine Resources | Documentation

JonasObertuefer · Answer

Hi @MonicaClayton,

There is way to do this in CityEngine although it is a rather complex workflow:

Asumming you have the landuse and footprint shapes in a different shape layer

* Select all landuse shapes
* Apply & Generate the following CGA on them:attr landuse = "residential"

Lot --> 
	t(0,-5,0)  
	extrude(10)
	label(landuse)
	color(1,0,0.5)​

* Connect the object attribute to the landuse attribute in the Inspector, if they are not automatically connected
* Select all footprints and assign&generate the following CGA onto them:Lot -->
	contextCheck

contextCheck -->
	case inside(inter, "residential") : 
		color(1,0,1) 
		report("landuse", "residential") 
		extrude(15)
	// add more cases for all usages
	else: extrude(15)​

* Add a new python file to the Scripts folder of the projectfrom scripting import *

# Get a CityEngine instance
ce = CE()

# Called for each shape after generation.
def finishModel(exportContextOID, shapeOID, modelOID):
    ctx = ScriptExportModelSettings(exportContextOID)
    shape = Shape(shapeOID)
    model = Model(modelOID)

reports = model.getReports()
    if 'landuse' in reports:
        ce.setAttribute(shape, "landuse", reports['landuse'][0])​

* With the footprints still selected go to File -> Export -> Script Based Export (Python). Select the previously created python script and click on Finish
* All footprints inside a landuse shape will have a new landuse object attribute with the value of their respective surrounding landuse shape.
* Select them using your python script from above

I hope this is what you want to achieve. Let me know if you have any questions!

Cheers
Jonas

MonicaClayton · Answer

I did, and it gave me the same results. I want to select the footprints that are within the already selected land use polygons. Like my edit, a "Select by Location" option and the location being within my already selected polygons. Is this possible? There isn't any specific or differentiating attribute on the footprints that I can use to pick them out, the only thing they all have in common is the fact they are within a polygon tagged as "landuse, residential".

Thank you for the help!!