Topic: How to select boundary points on pure Hatch?

[ken2023]

I create a hatch using the AutoCAD .NET,  and here is my code:

Code - C#: [Select]

1.             var pts = new Point2d[]
2.             {
3.                 new Point2d(10, 0),
4.                 new Point2d(10, 10),
5.                 new Point2d(20, 10),
6.                 new Point2d(20, 0),
7.                 new Point2d(10, 0),
8.             };
9.             var ptCol = new Point2dCollection(pts);
10.             var doubleCol = new DoubleCollection();
11.  
12.             var doc = Acap.DocumentManager.MdiActiveDocument;
13.             using (var tran = doc.Database.TransactionManager.StartTransaction())
14.             {
15.                 var table = tran.GetObject(doc.Database.BlockTableId, OpenMode.ForRead) as BlockTable;
16.                 var record = tran.GetObject(table[BlockTableRecord.ModelSpace], OpenMode.ForWrite) as BlockTableRecord;
17.  
18.                 var hatch = new Hatch();
19.                 record.AppendEntity(hatch);
20.  
21.                 hatch.AppendLoop(HatchLoopTypes.Default, ptCol, doubleCol);
22.                 hatch.EvaluateHatch(true);
23.  
24.                 tran.AddNewlyCreatedDBObject(hatch, true);
25.                 tran.Commit();
26.  
27.             }
28.  

The code works well, and I can see a hatch in the AutoCAD interface.

Now I want to draw a line, so I use "line" command, but I can't pick a point on the Hatch I created.
I hope to pick boundary points on Hatch, even if there is no Polyline around Hatch.

I have searched for some information, and I may need to customize an entity using C++ to realize the function. I hope to obtain a more concise solution.

Thanks a lot.

[gile]

Hi,

You can create a custom object snap for the hatch boundary vertices.

The value of OSPTIONS sysvar must not include 1 (i.e. 0, 2, 4 or 6).

Code - C#: [Select]

1. using Autodesk.AutoCAD.DatabaseServices;
2. using Autodesk.AutoCAD.Geometry;
3. using Autodesk.AutoCAD.GraphicsInterface;
4. using Autodesk.AutoCAD.Runtime;
5.  
6. namespace HatchBoundaryOsnap
7. {
8.     internal class HatchBoundOsnap
9.     {
10.         public static void Create()
11.         {
12.             var hatchBoundGlyph = new HatchBoundGlyph();
13.             var hatchBoundSnapMode = new CustomObjectSnapMode("HBV", "HBV", "Hatch boundary vertex", hatchBoundGlyph);
14.             var hatchBoundInfo = new HatchBoundInfo();
15.             hatchBoundSnapMode.ApplyToEntityType(RXObject.GetClass(typeof(Hatch)), new AddObjectSnapInfo(HatchBoundInfo.VertexInfo));
16.         }
17.  
18.         class HatchBoundGlyph : Glyph
19.         {
20.             private Point3d point;
21.  
22.             public override void SetLocation(Point3d point)
23.             {
24.                 this.point = point;
25.             }
26.  
27.             protected override void SubViewportDraw(ViewportDraw vd)
28.             {
29.                 int glyphPixels = CustomObjectSnapMode.GlyphSize;
30.                 Point2d glyphSize = vd.Viewport.GetNumPixelsInUnitSquare(point);
31.                 double offset = (glyphPixels / glyphSize.Y) * 0.8;
32.                 var points = new Point3dCollection
33.                 {
34.                     new Point3d(point.X, point.Y - offset, point.Z),
35.                     new Point3d(point.X + offset, point.Y, point.Z),
36.                     new Point3d(point.X, point.Y + offset, point.Z),
37.                     new Point3d(point.X - offset, point.Y, point.Z),
38.                     new Point3d(point.X, point.Y - offset, point.Z),
39.                 };
40.                 vd.Geometry.DeviceContextPolygon(points);
41.             }
42.         }
43.  
44.         class HatchBoundInfo
45.         {
46.             public static void VertexInfo(ObjectSnapContext context, ObjectSnapInfo result)
47.             {
48.                 if (context.PickedObject is Hatch hatch)
49.                 {
50.                     var xform = Matrix3d.PlaneToWorld(new Plane(Point3d.Origin, hatch.Normal));
51.                     double elevation = hatch.Elevation;
52.                     Point3d convert3d(Point2d pt) =>
53.                         new Point3d(pt.X, pt.Y, elevation).TransformBy(xform);
54.                     for (int i = 0; i < hatch.NumberOfLoops; i++)
55.                     {
56.                         var loop = hatch.GetLoopAt(i);
57.                         if (loop.IsPolyline)
58.                         {
59.                             foreach (BulgeVertex vertex in loop.Polyline)
60.                             {
61.                                 result.SnapPoints.Add(convert3d(vertex.Vertex));
62.                             }
63.                         }
64.                         else
65.                         {
66.                             foreach (Curve2d curve in loop.Curves)
67.                             {
68.                                 result.SnapPoints.Add(convert3d(curve.StartPoint));
69.                             }
70.                         }
71.                     }
72.                 }
73.             }
74.         }
75.     }
76. }
77.  

To have this osnap available, simply call the HatchBoundOsnap.Create() method in the Initialize method of a class implementing IExtensionApplication.

Code - C#: [Select]

1. using Autodesk.AutoCAD.ApplicationServices.Core;
2. using Autodesk.AutoCAD.Runtime;
3.  
4. using System;
5.  
6. namespace HatchBoundaryOsnap
7. {
8.     public class Initialization : IExtensionApplication
9.     {
10.         public void Initialize()
11.         {
12.             HatchBoundOsnap.Create();
13.         }
14.  
15.         public void Terminate()
16.         { }
17.     }
18. }
19.  

You can have a look at the attached screencast.

[ken2023]

I really appreciate this.