3D intersection of 2 3D polylines with Python

07-03-2018 06:48 AM
New Contributor

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



#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):



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


del cursor

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

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5 Replies
MVP Honored Contributor

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? 

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New Contributor

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)?

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MVP Honored Contributor

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.

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New Contributor

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

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MVP Honored Contributor

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.

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