segment intersections

[battler.]

Hi all,

A bunch of lines (segments) which are defined by a Start XY and End XY co-ordinates. 

These segments overlap to form a GRID.  I must find and divide these segments at their intersections.

The image below shows 4 segments (black lines) which intersect (intersections highlighted by red circle).  The result for this example should be 12 segments which are connected are their endpoints only.

Message Edited by battler. on 05-21-2010 07:48 PM

Message Edited by battler. on 05-21-2010 07:51 PM

[battler.]

I have implemented a method of finding Segment-Segment intersections based on the code given in "Computational Geometry in C." by Joseph O'Rourke.  However, I want to be able to do this reliably and this code does not deal well with the issues with floating point numbers.

Are there in-built tools in LabVIEW which can do (or help me to do) what I want with these segments (i.e. to find segment intersections, or to build a grid from segments)?  Currently I am looking at (but have never used) the MathScript functions.

Does anybody know how to solve this problem?

[Hueter]

If you know the start and end point you can calculate the slope (rise/run) then translate the line so it crosses the start point. Once you do these two things you should have a polynomial for your line. Then you simply solve one equation for the other to find the intersection. Once you have the intersections, you can build your line segments.

[battler.]

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Hueter wrote:
If you know the start and end point you can calculate the slope (rise/run) then translate the line so it crosses the start point. Once you do these two things you should have a polynomial for your line. Then you simply solve one equation for the other to find the intersection. Once you have the intersections, you can build your line segments.

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That's a valid although inefficient way of doing it.

Are there any in-built tools available in LV to find segment(vector) intersections?

[F._Schubert]

I'd start with the approach Hueter suggested. But the equations will form a set of linear equations which you can solve using linear algebra functions. I'm not into LA, but if I remember correctly, that was one of the indroduction use cases for that topic.

Felix 

[bparveen]

I would also be interested in an answer to this one and any ideas.  We are looking at glass fibre length distributions and crossing fibres pose real problems.

I have attached a thresholded image showing a typical distribution.

[altenbach]

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@bparveen wrote:

We are looking at glass fibre length distributions and crossing fibres pose real problems.

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This is a completely different problem and I would recommend that you start a new thread.

This thread is about finding line segments seperated by crossover points, while you are looking for the lenghts of the entire fibers, ignoring any crossovers.