Topic: Best way to create Polyline3d from 2 lines and an Arc

[Keith Brown]

For some reason I am struggling with this.  I see lots of examples of creating a 2d polyline but i need to combine lines and arcs in 3d space.  Can anyone point out an example?  Thank you.

[kpblc]

3d polyline can't have arcs. You have to create spline, i think

[Jochen]

KPbIC is right.
But if you can live with "arcs" consisting of short straight lines, so you can find a free download of PEDIT3D.vlx at
www.ant-ares.de
regards
Jochen
 

[SEANT]

To continue in the "kpblc is right" vein, a NURBS based spline can combine straight and arc like segments.

https://knowledge.autodesk.com/support/autocad/learn-explore/caas/screencast/Main/Details/5e33242a-03aa-493f-b2da-102408f3f945.html

Of course, splines come with their own set of issues - not the least of which is that they are a handfull to work with programatically.

If you do consider splines a possible solution, Look at the Autodesk.AutoCAD.DatabaseServices.Entity.JoinEntities and/or Autodesk.AutoCAD.Geometry.NurbCurve3d.JoinWith methods.

[gile]

Hi,

If the arc and the lines lies on the same plane, you can try to join them into a polyline. You have to search which start point or end point are corresponding.

Here's a little example to make a polyline from 2 lines and one arc with the arc between the lines.

Code - C#: [Select]

1.         private Polyline Join(Arc arc, Line line1, Line line2, Tolerance tolerance)
2.         {
3.             var plane = arc.GetPlane();
4.             if (!(plane.IsOn(line1.StartPoint) && plane.IsOn(line1.EndPoint) &&
5.                 plane.IsOn(line2.StartPoint) && plane.IsOn(line2.EndPoint)))
6.                 return null;
7.  
8.             Point2d p0, p3;
9.             var p1 = arc.StartPoint.Convert2d(plane);
10.             var p2 = arc.EndPoint.Convert2d(plane);
11.             var start1 = line1.StartPoint.Convert2d(plane);
12.             var end1 = line1.EndPoint.Convert2d(plane);
13.             var start2 = line2.StartPoint.Convert2d(plane);
14.             var end2 = line2.EndPoint.Convert2d(plane);
15.  
16.             if (start1.IsEqualTo(p1, tolerance))
17.             {
18.                 p0 = end1;
19.                 if (start2.IsEqualTo(p2, tolerance)) p3 = end2;
20.                 else if (end2.IsEqualTo(p2, tolerance)) p3 = start2;
21.                 else return null;
22.             }
23.             else if (end1.IsEqualTo(p1, tolerance))
24.             {
25.                 p0 = start1;
26.                 if (start2.IsEqualTo(p2, tolerance)) p3 = end2;
27.                 else if (end2.IsEqualTo(p2, tolerance)) p3 = start2;
28.                 else return null;
29.             }
30.             else if (start2.IsEqualTo(p1, tolerance))
31.             {
32.                 p0 = end2;
33.                 if (start1.IsEqualTo(p2, tolerance)) p3 = end1;
34.                 else if (end1.IsEqualTo(p2, tolerance)) p3 = start1;
35.                 else return null;
36.             }
37.             else if (end2.IsEqualTo(p1, tolerance))
38.             {
39.                 p0 = line2.StartPoint.Convert2d(plane);
40.                 if (start1.IsEqualTo(p2, tolerance)) p3 = end1;
41.                 else if (end1.IsEqualTo(p2, tolerance)) p3 = start1;
42.                 else return null;
43.             }
44.             else
45.             {
46.                 return null;
47.             }
48.             var angle = arc.EndAngle - arc.StartAngle;
49.             if (angle < 0)
50.                 angle += Math.PI * 2.0;
51.             double bulge = Math.Tan(angle / 4.0);
52.  
53.             Polyline pline = new Polyline(4);
54.             pline.AddVertexAt(0, p0, 0.0, 0.0, 0.0);
55.             pline.AddVertexAt(1, p1, bulge, 0.0, 0.0);
56.             pline.AddVertexAt(2, p2, 0.0, 0.0, 0.0);
57.             pline.AddVertexAt(3, p3, 0.0, 0.0, 0.0);
58.             pline.Normal = arc.Normal;
59.             pline.TransformBy(Matrix3d.Displacement(arc.Center.GetAsVector()));
60.             return pline;
61.         }

You can also use the PolylineSegmentCollection.join() method from GeometryExtensions.

[gile]

Here's an example using GeometryExtensions PolylineSegmentCollection.Join() method.
All contiguous lines and arcs in the selection set which lie on the reference arc plane are joined into polylines.

Code - C#: [Select]

1.         [CommandMethod("TEST")]
2.         public void Test()
3.         {
4.             var doc = Application.DocumentManager.MdiActiveDocument;
5.             var db = doc.Database;
6.             var ed = doc.Editor;
7.  
8.             var arcOpts = new PromptEntityOptions("\nSelect the reference arc: ");
9.             arcOpts.SetRejectMessage("\nSelected object is not an arc.");
10.             arcOpts.AddAllowedClass(typeof(Arc), true);
11.             var arcRes = ed.GetEntity(arcOpts);
12.             if (arcRes.Status != PromptStatus.OK)
13.                 return;
14.             var arcId = arcRes.ObjectId;
15.  
16.             var selSet = ed.GetSelection(new SelectionFilter(new[] { new TypedValue(0, "ARC,LINE") }));
17.             if (selSet.Status != PromptStatus.OK)
18.                 return;
19.  
20.             using (var tr = db.TransactionManager.StartTransaction())
21.             {
22.                 var arc = (Arc)tr.GetObject(arcId, OpenMode.ForRead);
23.                 var normal = arc.Normal;
24.                 var plane = arc.GetPlane();
25.                 var displace = Matrix3d.Displacement(arc.Center.GetAsVector());
26.                 var segments = new PolylineSegmentCollection();
27.                 segments.Add(new PolylineSegment(
28.                     new CircularArc2d(
29.                         arc.StartPoint.Convert2d(plane),
30.                         arc.GetPointAtParameter((arc.StartParam + arc.EndParam) / 2.0).Convert2d(plane),
31.                         arc.EndPoint.Convert2d(plane))));
32.                 foreach (var id in selSet.Value.GetObjectIds())
33.                 {
34.                     if (id == arcId)
35.                         continue;
36.  
37.                     if (id.ObjectClass.DxfName == "ARC")
38.                     {
39.                         arc = (Arc)tr.GetObject(id, OpenMode.ForRead);
40.                         if (arc.Normal.IsEqualTo(normal))
41.                         {
42.                             segments.Add(new PolylineSegment(
43.                                 new CircularArc2d(
44.                                     arc.StartPoint.Convert2d(plane),
45.                                     arc.GetPointAtParameter((arc.StartParam + arc.EndParam) / 2.0).Convert2d(plane),
46.                                     arc.EndPoint.Convert2d(plane))));
47.                         }
48.                     }
49.                     else
50.                     {
51.                         var line = (Line)tr.GetObject(id, OpenMode.ForRead);
52.                         if (plane.IsOn(line.StartPoint) && plane.IsOn(line.EndPoint))
53.                         {
54.                             segments.Add(new PolylineSegment(
55.                                 new LineSegment2d(
56.                                     line.StartPoint.Convert2d(plane),
57.                                     line.EndPoint.Convert2d(plane))));
58.                         }
59.                     }
60.                 }
61.  
62.                 var curSpace = (BlockTableRecord)tr.GetObject(db.CurrentSpaceId, OpenMode.ForWrite);
63.                 foreach (var pline in segments.Join().Select(s => s.ToPolyline()))
64.                 {
65.                     curSpace.AppendEntity(pline);
66.                     tr.AddNewlyCreatedDBObject(pline, true);
67.                     pline.Normal = normal;
68.                     pline.TransformBy(displace);
69.                 }
70.  
71.                 tr.Commit();
72.             }
73.         }

[Keith Brown]

Thank you all for the help.


Gile, I use your Geometry Extensions quite a bit and the part that I was missing was using the arc plane and converting everything to 2D.  Now that I have that missing piece the rest is cake.  Thank you once again.