Testing whether a point is on an AutoCAD polyline using .NET

csharp

Testing whether a point is on an AutoCAD polyline using .NET



Occasionally I come across a topic that I’m sure I’ve addressed in a previous post, but for the life of me I can’t track it down. The code in a recent response by Balaji Ramamoorthy, from the DevTech India team, fits firmly into this category: it shows how to iterate through a polyline’s segments, testing whether a point is on the polyline.

I did some refactoring of Balaji’s code to extract it into a helper function (although not an extension method, which people who use them may prefer), but otherwise this C# code is basically his.

1. using Autodesk.AutoCAD.ApplicationServices;
   
2. 
   
3. using Autodesk.AutoCAD.DatabaseServices;
   
4. 
   
5. using Autodesk.AutoCAD.EditorInput;
   
6. 
   
7. using Autodesk.AutoCAD.Geometry;
   
8. 
   
9. using Autodesk.AutoCAD.Runtime;
   
10. 
    
11. 
    
12. 
    
13. namespace PolylineTesting
    
14. 
    
15. {
    
16. 
    
17.   public class Commands
    
18. 
    
19.   {
    
20. 
    
21.     [CommandMethod("POP")]
    
22. 
    
23.     public void PointOnPolyline()
    
24. 
    
25.     {
    
26. 
    
27.       Document doc =
    
28. 
    
29.         Application.DocumentManager.MdiActiveDocument;
    
30. 
    
31.       Database db = doc.Database;
    
32. 
    
33.       Editor ed = doc.Editor;
    
34. 
    
35. 
    
36. 
    
37.       PromptEntityOptions peo =
    
38. 
    
39.         new PromptEntityOptions("\nSelect a polyline");
    
40. 
    
41.       peo.SetRejectMessage("Please select a polyline");
    
42. 
    
43.       peo.AddAllowedClass(typeof(Polyline), true);
    
44. 
    
45. 
    
46. 
    
47.       PromptEntityResult per = ed.GetEntity(peo);
    
48. 
    
49.       if (per.Status != PromptStatus.OK)
    
50. 
    
51.         return;
    
52. 
    
53. 
    
54. 
    
55.       PromptPointResult ppr = ed.GetPoint("\nSelect a point");
    
56. 
    
57.       if (ppr.Status != PromptStatus.OK)
    
58. 
    
59.         return;
    
60. 
    
61. 
    
62. 
    
63.       Transaction tr = db.TransactionManager.StartTransaction();
    
64. 
    
65.       using (tr)
    
66. 
    
67.       {
    
68. 
    
69.         Polyline polyline =
    
70. 
    
71.           tr.GetObject(per.ObjectId, OpenMode.ForRead) as Polyline;
    
72. 
    
73.         if (polyline != null)
    
74. 
    
75.         {
    
76. 
    
77.           bool isOn = IsPointOnPolyline(polyline, ppr.Value);
    
78. 
    
79.           ed.WriteMessage(
    
80. 
    
81.             "\nSelected point is {0}on the polyline.",
    
82. 
    
83.             isOn ? "" : "not "
    
84. 
    
85.           );
    
86. 
    
87.         }
    
88. 
    
89.         tr.Commit();
    
90. 
    
91.       }
    
92. 
    
93.     }
    
94. 
    
95. 
    
96. 
    
97.     private bool IsPointOnPolyline(Polyline pl, Point3d pt)
    
98. 
    
99.     {
    
100. 
     
101.       bool isOn = false;
     
102. 
     
103.       for (int i = 0; i < pl.NumberOfVertices; i++)
     
104. 
     
105.       {
     
106. 
     
107.         Curve3d seg = null;
     
108. 
     
109. 
     
110. 
     
111.         SegmentType segType = pl.GetSegmentType(i);
     
112. 
     
113.         if (segType == SegmentType.Arc)
     
114. 
     
115.           seg = pl.GetArcSegmentAt(i);
     
116. 
     
117.         else if (segType == SegmentType.Line)
     
118. 
     
119.           seg = pl.GetLineSegmentAt(i);
     
120. 
     
121. 
     
122. 
     
123.         if (seg != null)
     
124. 
     
125.         {
     
126. 
     
127.           isOn = seg.IsOn(pt);
     
128. 
     
129.           if (isOn)
     
130. 
     
131.             break;
     
132. 
     
133.         }
     
134. 
     
135.       }
     
136. 
     
137.       return isOn;
     
138. 
     
139.     }
     
140. 
     
141.   }
     
142. 
     
143. }
     

using Autodesk.AutoCAD.ApplicationServices;<br /> <br /> using Autodesk.AutoCAD.DatabaseServices;<br /> <br /> using Autodesk.AutoCAD.EditorInput;<br /> <br /> using Autodesk.AutoCAD.Geometry;<br /> <br /> using Autodesk.AutoCAD.Runtime;<br /> <br /> <br /> <br /> namespace PolylineTesting<br /> <br /> {<br /> <br />   public class Commands<br /> <br />   {<br /> <br />     [CommandMethod("POP")]<br /> <br />     public void PointOnPolyline()<br /> <br />     {<br /> <br />       Document doc =<br /> <br />         Application.DocumentManager.MdiActiveDocument;<br /> <br />       Database db = doc.Database;<br /> <br />       Editor ed = doc.Editor;<br /> <br /> <br /> <br />       PromptEntityOptions peo =<br /> <br />         new PromptEntityOptions("\nSelect a polyline");<br /> <br />       peo.SetRejectMessage("Please select a polyline");<br /> <br />       peo.AddAllowedClass(typeof(Polyline), true);<br /> <br /> <br /> <br />       PromptEntityResult per = ed.GetEntity(peo);<br /> <br />       if (per.Status != PromptStatus.OK)<br /> <br />         return;<br /> <br /> <br /> <br />       PromptPointResult ppr = ed.GetPoint("\nSelect a point");<br /> <br />       if (ppr.Status != PromptStatus.OK)<br /> <br />         return;<br /> <br /> <br /> <br />       Transaction tr = db.TransactionManager.StartTransaction();<br /> <br />       using (tr)<br /> <br />       {<br /> <br />         Polyline polyline =<br /> <br />           tr.GetObject(per.ObjectId, OpenMode.ForRead) as Polyline;<br /> <br />         if (polyline != null)<br /> <br />         {<br /> <br />           bool isOn = IsPointOnPolyline(polyline, ppr.Value);<br /> <br />           ed.WriteMessage(<br /> <br />             "\nSelected point is {0}on the polyline.",<br /> <br />             isOn ? "" : "not "<br /> <br />           );<br /> <br />         }<br /> <br />         tr.Commit();<br /> <br />       }<br /> <br />     }<br /> <br /> <br /> <br />     private bool IsPointOnPolyline(Polyline pl, Point3d pt)<br /> <br />     {<br /> <br />       bool isOn = false;<br /> <br />       for (int i = 0; i < pl.NumberOfVertices; i++)<br /> <br />       {<br /> <br />         Curve3d seg = null;<br /> <br /> <br /> <br />         SegmentType segType = pl.GetSegmentType(i);<br /> <br />         if (segType == SegmentType.Arc)<br /> <br />           seg = pl.GetArcSegmentAt(i);<br /> <br />         else if (segType == SegmentType.Line)<br /> <br />           seg = pl.GetLineSegmentAt(i);<br /> <br /> <br /> <br />         if (seg != null)<br /> <br />         {<br /> <br />           isOn = seg.IsOn(pt);<br /> <br />           if (isOn)<br /> <br />             break;<br /> <br />         }<br /> <br />       }<br /> <br />       return isOn;<br /> <br />     }<br /> <br />   }<br /> <br /> }<br />

When you run the POP command and select a polyline and a point, you’ll see a message on the command-line indicating whether the latter is on the former

[url]http://through-the-interface.typepad.com/through_the_interface/2012/01/testing-whether-a-point-is-on-an-autocad-polyline-using-net.html[/url]