Hatch Loop using a Curve2d collection

By Balaji Ramamoorthy

To create a hatch, the loop information can be provided by providing the ObjectId collection of the database-resident entities that define the hatch loop. For this please refer to this post : Create Hatch Objects using Trace Boundaries using .NET. The other way is to only rely on the geometry without having the entities added to the database.

Here is a sample code to demonstrate the second approach that creates the hatch loop only using the boundary geometry. To have two loops created for the same hatch, the sample code prompts for two internal points to be picked.

[CommandMethod("TH")]
public void TestHatch()
{
    Document doc = Application.DocumentManager.MdiActiveDocument;
    Database db = doc.Database;
    Editor ed = doc.Editor;
 
    PromptPointResult ppr1 
                 = ed.GetPoint("Pick an internal point 1 : ");
    if (ppr1.Status != PromptStatus.OK)
        return;
    Point3d internalPt1 = ppr1.Value;
    DBObjectCollection dbo1 
                        = ed.TraceBoundary(internalPt1, true);
    if (dbo1 == null)
        return;
 
    PromptPointResult ppr2 
                  = ed.GetPoint("Pick an internal point 2 : ");
    if (ppr2.Status != PromptStatus.OK)
        return;
    Point3d internalPt2 = ppr2.Value;
    DBObjectCollection dbo2 
                        = ed.TraceBoundary(internalPt2, true);
    if (dbo2 == null)
        return;
 
    try
    {
        using (Transaction tr 
                   = db.TransactionManager.StartTransaction())
        {
            BlockTable bt = tr.GetObject(
                                            db.BlockTableId, 
                                            OpenMode.ForWrite
                                        ) as BlockTable;
            BlockTableRecord btr = tr.GetObject
                            (
                               bt[BlockTableRecord.ModelSpace], 
                               OpenMode.ForWrite
                            ) as BlockTableRecord;
 
            Curve2dCollection edgePtrs1 = new Curve2dCollection();
            IntegerCollection edgeTypes1 = new IntegerCollection();
            foreach (DBObject obj in dbo1)
            {
                Entity entity = obj as Entity;
                Autodesk.AutoCAD.DatabaseServices.Polyline pline 
                = entity as Autodesk.AutoCAD.DatabaseServices.Polyline;
                if (pline != null)
                {
                    GetEdgeInformation( pline, 
                                        ref edgePtrs1, 
                                        ref  edgeTypes1);
                }
            }
 
            Curve2dCollection edgePtrs2 = new Curve2dCollection();
            IntegerCollection edgeTypes2 = new IntegerCollection();
            foreach (DBObject obj in dbo2)
            {
                Entity entity = obj as Entity;
                Autodesk.AutoCAD.DatabaseServices.Polyline pline 
                = entity as Autodesk.AutoCAD.DatabaseServices.Polyline;
                if (pline != null)
                {
                    GetEdgeInformation( pline, 
                                        ref edgePtrs2, 
                                        ref  edgeTypes2);
                }
            }
 
            Hatch hatchObj = new Hatch();
            hatchObj.SetDatabaseDefaults();
 
            Vector3d normal = new Vector3d(0.0, 0.0, 1.0);
            hatchObj.HatchObjectType = HatchObjectType.HatchObject;
            hatchObj.Color 
                    = Autodesk.AutoCAD.Colors.Color.FromColor
                                    (System.Drawing.Color.Blue);
 
            hatchObj.Normal = normal;
            hatchObj.Elevation = 0.0;
            hatchObj.PatternScale = 0.5;
            hatchObj.SetHatchPattern
                                (
                                    HatchPatternType.PreDefined, 
                                    "ZIGZAG"
                                );
 
            btr.AppendEntity(hatchObj);
            tr.AddNewlyCreatedDBObject(hatchObj, true);
 
            hatchObj.Associative = true;
            hatchObj.AppendLoop(
                                (int)HatchLoopTypes.Default, 
                                edgePtrs1, 
                                edgeTypes1
                                );
            hatchObj.AppendLoop(
                                (int)HatchLoopTypes.Default, 
                                edgePtrs2, 
                                edgeTypes2
                               );
 
            hatchObj.EvaluateHatch(true);
 
            tr.Commit();
        }
    }
    catch (System.Exception ex)
    {
        ed.WriteMessage(ex.ToString() + Environment.NewLine);
    }
}
 
public void GetEdgeInformation
        (
            Autodesk.AutoCAD.DatabaseServices.Polyline pline, 
            ref Curve2dCollection plCurves, 
            ref IntegerCollection edgeTypes
        )
{
    int segCount = pline.NumberOfVertices;
    for (int cnt = 0; cnt < segCount; cnt++)
    {
        SegmentType type = pline.GetSegmentType(cnt);
 
        switch (type)
        {
            case SegmentType.Arc:
                CircularArc2d arc2d = pline.GetArcSegment2dAt(cnt);
                plCurves.Add(arc2d);
                edgeTypes.Add((int)Enum.Parse(typeof(HatchEdgeType),
                        HatchEdgeType.CircularArc.ToString()));
                break;
 
            case SegmentType.Line:
                LineSegment2d line2d = pline.GetLineSegment2dAt(cnt);
                plCurves.Add(line2d);
                edgeTypes.Add((int)Enum.Parse(typeof(HatchEdgeType),
                               HatchEdgeType.Line.ToString()));
                break;
 
            case SegmentType.Coincident:
                break;
            case SegmentType.Empty:
                break;
            case SegmentType.Point:
                break;
        }
    }
}

Here is a sample output for two loops that were appended and a sample drawing for you to try :

Download Test