Topic: Polyline overlap

[hojjat]

Using C# 7.3, Visual Studio 2022 and Autocad 2013:

Is there any function to compare two polylines for area overlap?
I want to compare two polylines and detect area overlapping.
Polyline segments can be LineSegment2d or CircularArc2d.
My purpose is a function that returns false if they are only tangent or non-overlapping, and returns true if they have overlap with a specific tolerance.

Thanks

[gile]

Hi,

You can create regions from the polyline and check if the intersection boolean operation generates an area greater than 0.

Code - C#: [Select]

1.         public static double OverlapArea(Polyline pline1, Polyline pline2)
2.         {
3.             using (var region1 = CreateRegion(pline1))
4.             using (var region2 = CreateRegion(pline2))
5.             {
6.                 if (region1 != null && region2 != null)
7.                 {
8.                     region1.BooleanOperation(BooleanOperationType.BoolIntersect, region2);
9.                     return region1.Area;
10.                 }
11.                 return 0.0;
12.             }
13.         }
14.  
15.         private static Region CreateRegion(Polyline pline)
16.         {
17.             var curves = new DBObjectCollection { pline };
18.             var regions =  Region.CreateFromCurves(curves);
19.             switch (regions.Count)
20.             {
21.                 case 0:
22.                     return null;
23.                 case 1:
24.                     return (Region)regions[0];
25.                 default:
26.                     foreach (DBObject dBObject in regions) dBObject.Dispose();
27.                     return null;
28.             }
29.         }

A testing command:

Code - C#: [Select]

1.         [CommandMethod("TEST")]
2.         public static void Test()
3.         {
4.             var doc = AcAp.DocumentManager.MdiActiveDocument;
5.             var db = doc.Database;
6.             var ed = doc.Editor;
7.  
8.             var options = new PromptEntityOptions("\nSelect first polyline: ");
9.             options.SetRejectMessage("\nSelected object is not a Polyline.");
10.             options.AddAllowedClass(typeof(Polyline), true);
11.             var result = ed.GetEntity(options);
12.             if (result.Status != PromptStatus.OK)
13.                 return;
14.             var id1 = result.ObjectId;
15.  
16.             options.Message = "\nSelect second polyline: ";
17.             result = ed.GetEntity(options);
18.             if (result.Status != PromptStatus.OK)
19.                 return;
20.             var id2 = result.ObjectId;
21.  
22.             using (var tr = db.TransactionManager.StartTransaction())
23.             {
24.                 var pline1 = (Polyline)tr.GetObject(id1, OpenMode.ForRead);
25.                 var pline2 = (Polyline)tr.GetObject(id2, OpenMode.ForRead);
26.                 double area = OverlapArea(pline1, pline2);
27.                 if (0.0 < area)
28.                     ed.WriteMessage($"\nPolylines overlap ({area:0.00} square units).");
29.                 else
30.                     ed.WriteMessage("\nPolylines do not overlap.");
31.                 tr.Commit();
32.             }
33.         }

[hojjat]

Thank you very much Gile, It works properly.