Topic: Overlapping area 2 closed lwpolylines

[Peter Guappa]

Starting with 2 closed lwpolylines (partially overlapping), I'm looking for a solution (lisp) to calculate/create a third polyline which is the boundary of the overlapping area.

The 2 starting polylines have no bulges, only lines.

Can somebody help me out?


Thanks!!!

[TheMaster]

Starting with 2 closed lwpolylines (partially overlapping), I'm looking for a solution (lisp) to calculate/create a third polyline which is the boundary of the overlapping area.

The 2 starting polylines have no bulges, only lines.

Can somebody help me out?


Thanks!!!

Unless I'm missing something, the solution seems very straightforward.

Create a region from each of the two polylines, then use the INTERSECT command to obtain the intersection, explode the resulting region and create a new polyline from the exploded lines.

[Peter Guappa]

Thanks, I will give it a try

[Tharwat]

Use the command boundary and pick a point in the center of the tow polylines

[irneb]

Create a region from each of the two polylines, then use the INTERSECT command to obtain the intersection, explode the resulting region and create a new polyline from the exploded lines.

You might want to set the DelObj (http://docs.autodesk.com/ACD/2010/ENU/AutoCAD%202010%20User%20Documentation/index.html?url=WS1a9193826455f5ffa23ce210c4a30acaf-6877.htm,topicNumber=d0e95128) system variable to 0 before running the Region command. That way your original polylines are left as is.

Also, if you're only after the area of the intersection, then the region object also has an area property - you need not explode it and convert to another polyline.

[gile]

Hi,

Maybe you can get some inspiration this thread (a LISP implementation in reply #3).
It uses the method puposed by Tony for a different task (unioning region instead of intersecting them), but you can adapt it to your suit replacing acUnion with acIntersection.

[Peter Guappa]

Thank you all!
Enough info to get me started and reach my goal.
Cheers

[TheMaster]

You might want to set the DelObj (http://docs.autodesk.com/ACD/2010/ENU/AutoCAD%202010%20User%20Documentation/index.html?url=WS1a9193826455f5ffa23ce210c4a30acaf-6877.htm,topicNumber=d0e95128) system variable to 0 before running the Region command. That way your original polylines are left as is.

Also, if you're only after the area of the intersection, then the region object also has an area property - you need not explode it and convert to another polyline.

If the OP needs the original polylines,

Code: [Select]

(if (not (entget <pline>)) (entdel <pline>)) will undelete them without the added burden of having to change/save/restore another sysvar.

[irneb]

Good point Tony! No need for error handling to reset the var back.

[Lee Mac]

You might want to set the DelObj system variable to 0 before running the Region command.

Alternatively you could use the ActiveX addregion method, followed by the boolean method whilst retaining all original objects.

[mianbaoche]

Do not want to use ActiveX addregion method the。

I try to complete his?

I hope to have a better algorithm！

[Tharwat]

Do not want to use ActiveX addregion method the。

Why not ?

[catoscuro]

use bpoly