Question

intersection of lines

  • 16 October 2014
  • 5 replies
  • 3 views

Badge +1
Hi,

 

 

I have 3d terrain data (with breaklines, formlines, points...) on which I'd like to compute (as points) or flag intersections. These intersections also include lines that cross on different heights (they intersect on 2d but not phisically on 3d) but exclude lines that are snapped on other lines (2d or 3d).

 

 

Does anyone have any idea?

 

 

Thank you

5 replies

Userlevel 4
Hi,

 

 

maybe the TopologyBuilder can help you along. You may need to use a 2DForcer first to make it ignore the Z-values.

 

 

David
Badge +1
yup, I tried that. It still gives me those unwanted intersections. Lots of them.

 

Userlevel 2
Badge +17
Hi, what kind of extra intersections have been created?

 

Takashi
Badge +3
You want "appearent intersections" and not true (3D) intersections?

 

 

 

One way could be to do topology in 2 or 3 planes by switching axes using only 2-axes and compare the results. Were they don't match, they are appearent.

 

 

Ofcourse you can just do vectormath in 3D...

 

Badge +1
Well, thank you all. And I apologize for not replying for quite a while. I've worked on a solution with another software (cleaned it with Autocad Map - Break crossings), but eventually used fme to determine duplicated endpoints with different Z-values.

 

 

So, Topology Builder giave me breaks on almost every vertex which isn't bad since then I could use to determine duplicated endpoints like I did. But it only works if I also use 2DForcer, and there lies a problem. I need those z-values in the end to determine type of intersection and select those that I need.

 

 

Logically, I expected to get a result with Intersector, MRF2DIntersector or MRF3DCleaner, but none of them gave me good breaks mostly due to type of input data (.dxf file with lines, 2Dpolylines and 3Dpolylines). For example, Intersector didn't gave breaks on appearent snaps of lines on 2Dpolylines, lines on lines, 2Dpolylines on lines and 2Dpolylines on 2Dpolylines. Interestingly, it gave breaks of lines and 2Dpolylines on 3Dpolylines. Other mentioned transformers also had problems with reading all of those lines (and yes, even if I used GeometryCoercer and reset all of them to fme_line).

 

 

I must admit that I don't understand Gio's reply, but like I sad the problem is solved. Hopefully SefeSoftware will update Intersector so that it gives every intersection.

 

 

Again, thank you all for help.

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