topic Re: 3D intersection of 2 3D polylines with Python in Python Questions

3D intersection of 2 3D polylines with Python

ashkanhassanzadeh — Tue, 03 Jul 2018 13:48:40 GMT

I am new to the arcpy. I searched the community and I didn't find the answer to the question.

I have problem with finding the intersection of two 3D polylines (each one with 2 vertex) with python in arcgis standard 10.5. Polylines are not in a .shp file, because they created using polyline1 = arcpy.polyline(...) so I can call them directly.

Using point = polyline1.intersect(polyline2 , 1) just create a multipoint class without anypoint in it.

I need the intersection point coordination (with z) as an answer

Also, I have problem with writing 3d polylines to .shp and .mdb files. after writing polylines to the file, the arcmap omit the z values and all the lines are horizontal.

So I really appriciate help with these 2 questions.

This is an example of the problems:

from os.path import expanduser
from os.path import join as joinadd
import os
import arcpy

#first question:

#2 below polylines obviously have intersection

#creating 3d polylines

polytemp1=arcpy.Polyline(arcpy.Array([arcpy.Point(1,2,1),arcpy.Point(10,11,10)]),"Unknown",True,False)

polytemp2=arcpy.Polyline(arcpy.Array([arcpy.Point(1,2,5),arcpy.Point(10,11,5)]),"Unknown",True,False)

#check for the intersection with disjoint

polytemp1.disjoint(polytemp2) #The answer is False, which means there is an intersection, but is disjoint check in 3D???? or just 2D????

#finding the point (3D)

pnt = polyline1.intersect(polyline2 , 1)

print 'newpoint' ,newpoint.pointCount, newpoint.type, newpoint.partCount #This shows that there is no point in the multipoint!!

#second question: writing a 3d polyline in a .shp file:

homeadd =joinadd(expanduser("~"),"arcgistemp")

if not os.path.exists(homeadd):

os.makedirs(homeadd)

arcpy.CreateFeatureclass_management(homeadd,"polyline1.shp","POLYLINE","","DISABLED","ENABLED","")

cursor = arcpy.da.InsertCursor(polyline1add, ["SHAPE@"])

cursor.insertRow([polyline1])

del cursor

#now I have the .shp file, but the lines are 2D!!

Re: 3D intersection of 2 3D polylines with Python

DarrenWiens2 — Wed, 04 Jul 2018 16:16:26 GMT

Question 1: change one of the z coordinates so that the lines clearly do not intersect along the z-axis, but still would intersect along the xy plane, to check.

Question 2: you go through a lot of work to create a feature class called 'homeadd', and then insert into a different feature class, 'polyline1add'. Is that intentional?

Re: 3D intersection of 2 3D polylines with Python

ashkanhassanzadeh — Wed, 04 Jul 2018 18:58:37 GMT

Thanks for the response Darren.

As I understand, .disjoint and .intersect just works in 2D (without Z).

Now the question is, 1. how to check if intersection exist in 3D? 2.How to find the intersection point (X,Y,Z)?

Re: 3D intersection of 2 3D polylines with Python

DarrenWiens2 — Wed, 04 Jul 2018 20:09:20 GMT

I suppose you could test if the lines intersect in 2D. If so, find the XY coordinates where they intersect. Calculate the Z coordinate at those locations. See if they're the same. If the lines don't intersect in 2D, they don't intersect in 3D.

Re: 3D intersection of 2 3D polylines with Python

ashkanhassanzadeh — Tue, 10 Jul 2018 09:15:38 GMT

The problem is If the lines have intersect in their 2D projection, it does not mean that they have intersect in 3D.

Re: 3D intersection of 2 3D polylines with Python

DarrenWiens2 — Tue, 10 Jul 2018 15:53:04 GMT

That's why I suggest calculate the Z-coordinates at the 2D intersection point. If it's the same for both line, then they intersect 3D.