VectorScript: Detect self-intersecting polygon/polylines

[caravanio]

Hello, all. Looking at the VectorScript function reference I see no functions that could tell whether a given polygon/polyline is self-intersecting. The only function that is told that it 

Quote

"... Should remove self-intersecting segments from the result. ..."

is the VS:OffsetPoly. But I don't want to see if a polygon/polyline is self intersecting as a side effect of an operation that actively acts on the selected object but just a read-only operation whether it is self-intersecting or not. Any suggestions are welcome.

[Matt Panzer]

Hi caravan,

 

Try the attached script. It has not been thoroughly tested but it seems to do the trick.

DoesPolySelfIntersectFunc.vs

[Matt Panzer]

I just played around with the script some more and realized that it only catches certain cases. The script basically creates two identical copies of the source poly and does an "intersect surface" on them. It will detect polys that intersect themselves like the poly to the right (in the attached image) because the "intersect surface" function will result in separate polys on each side of the intersection. So it does intersect surface, then counts to resultant polys. If there are more than one, the poly intersects. However, the poly on the left (in the image) will not be detected. I have some ideas of how this might be done but I need to spend a little more time.

 

[Miguel Barrera]

The long way would be to test each segment with the LineLineIntersection procedure

[Matt Panzer]

Yes, the long way is not as fun. ;-)

Try the revised script (attached).  I think this may do it for you.  I also added comments to explain what it's doing.

Let me know how it works for you if you use it.

DoesPolySelfIntersectFunc.vs

[trashcan]

Doesn't seem to work 😞 

[Matt Panzer]

Seems to work for me.

Can you attach a VWX file with the shape that it's not working on?

Also, what Version of Vectorworks did you try it on?