Curve.Extend

[Anonymous]

Hey guys, I am programming in C# and I am trying to extend the end point of a curve to another line and am having some trouble.

Could you by chance explain the Curve.Extend function to me, as well as what the syntax (bool extendStart, Point3d toPoint) means, and/or give an extend alternative if you have any.

[Alexander.Rivilis · Accepted solution]

Sample code:

using System;
using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Geometry;
using Autodesk.AutoCAD.EditorInput;

#pragma warning disable 0618

[assembly: CommandClass(typeof(ExtendLine.MyCommands))]

namespace ExtendLine
{
  public class MyCommands
  {
    [CommandMethod("ExtendLine")]
    public void MyCommand()
    {
      Document doc = Application.DocumentManager.MdiActiveDocument;
      if (doc == null) return;
      Editor ed = doc.Editor;
      PromptEntityResult rs1 = ed.GetEntity("\nSelect curve for extend operation: ");
      if (rs1.Status != PromptStatus.OK) return;
      if (!rs1.ObjectId.ObjectClass.IsDerivedFrom(RXClass.GetClass(typeof(Curve)))) {
        ed.WriteMessage("\nIt is not a Curve");
        return;
      }
      PromptEntityResult rs2 = ed.GetEntity("\nSelect boundary curve: ");
      if (rs2.Status != PromptStatus.OK) return;
      if (!rs2.ObjectId.ObjectClass.IsDerivedFrom(RXClass.GetClass(typeof(Curve)))) {
        ed.WriteMessage("\nIt is not a Curve");
        return;
      }
      using (Curve cv1 = rs1.ObjectId.Open(OpenMode.ForWrite) as Curve)
      using (Curve cv2 = rs2.ObjectId.Open(OpenMode.ForRead) as Curve) {
        Point3dCollection pts = new Point3dCollection();
        cv1.IntersectWith(cv2, Intersect.ExtendThis, pts, IntPtr.Zero, IntPtr.Zero);
        if (pts.Count > 0) {
          Point3d p = pts[0];
          Point3d pStart = cv1.StartPoint;
          Point3d pEnd = cv1.EndPoint;
          bool bStart = (p.DistanceTo(pStart) < p.DistanceTo(pEnd));
          try {
            cv1.Extend(bStart, p);
          }
          catch (Autodesk.AutoCAD.Runtime.Exception ex) {
            ed.WriteMessage(ex.ToString());
          }
        }
      }
    }
  }
}

[Anonymous]

So, I was able to make this work with my predetermined curves, but is there any way to extend it to the point at which the line WOULD intersect if cv2 kept going, but doesn't due to the line being too short to reach?

Example Image:

[Alexander.Rivilis · Accepted solution]

Try to replace this line of code:

cv1.IntersectWith(cv2, Intersect.ExtendThis, pts, IntPtr.Zero, IntPtr.Zero);

with this line:

cv1.IntersectWith(cv2, Intersect.ExtendBoth, pts, IntPtr.Zero, IntPtr.Zero);

[Anonymous]

If I could give you like ten Kudos per post, I would! Thanks a bunch!

[Anonymous]

So another question; how would I extend a line to the intersecting point, and then an additional 10 feet in the same direction?

[Anonymous]

Whoops, that last comment above was meant to be in reply to you.

[Alexander.Rivilis]

You have to use this algorithm to calculate point for extend: http://forums.autodesk.com/t5/net/how-to-get-point3d-between-two-point3d/m-p/6587893#M50386

[Anonymous]

In this case, would you modify the Point3dCollection to contact set values from that equation?

[Alexander.Rivilis · Accepted solution]

It is easy for me post a code:

using System;
using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Geometry;
using Autodesk.AutoCAD.EditorInput;

#pragma warning disable 0618

[assembly: CommandClass(typeof(ExtendLine.MyCommands))]

namespace ExtendLine
{
  public class MyCommands
  {
    [CommandMethod("ExtendLineWithOffset")]
    public void ExtendLineWithOffset()
    {
      Document doc = Application.DocumentManager.MdiActiveDocument;
      if (doc == null) return;
      Editor ed = doc.Editor;
      PromptEntityResult rs1 =
        ed.GetEntity("\nSelect curve to extend: ");
      if (rs1.Status != PromptStatus.OK) return;
      if (!rs1.ObjectId.ObjectClass.IsDerivedFrom(RXClass.GetClass(typeof(Curve))))
      {
        ed.WriteMessage("\nIt is not a curve!");
        return;
      }
      PromptEntityResult rs2 =
        ed.GetEntity("\nSelect boundary: ");
      if (rs2.Status != PromptStatus.OK) return;
      if (!rs2.ObjectId.ObjectClass.IsDerivedFrom(RXClass.GetClass(typeof(Curve))))
      {
        ed.WriteMessage("\nIt is not a Curve");
        return;
      }

      PromptDoubleResult rsOff = ed.GetDistance("\nOffset <0>: ");
      double offset = (rsOff.Status == PromptStatus.OK) ? rsOff.Value : 0;

      using (Curve cv1 = rs1.ObjectId.Open(OpenMode.ForWrite) as Curve)
      using (Curve cv2 = rs2.ObjectId.Open(OpenMode.ForRead) as Curve)
      {
        Point3dCollection pts = new Point3dCollection();
        cv1.IntersectWith(cv2, Intersect.ExtendBoth, pts, IntPtr.Zero, IntPtr.Zero);
        if (pts.Count > 0)
        {
          Point3d pStart = cv1.StartPoint;
          Point3d pEnd = cv1.EndPoint;
          Point3d p = pts[0];
          double dist = Math.Min(p.DistanceTo(pStart), p.DistanceTo(pEnd));
          bool bStart = (p.DistanceTo(pStart) < p.DistanceTo(pEnd));
          for (int i = 1; i < pts.Count; i++)
          {
            if (pts[i].DistanceTo(pStart) < dist)
            {
              p = pts[i]; bStart = true;
              dist = p.DistanceTo(pStart);
            }
            else if (pts[i].DistanceTo(pEnd) < dist)
            {
              p = pts[i]; bStart = false;
              dist = p.DistanceTo(pEnd);
            }
          }
          try
          {
            Vector3d dir = (p - ((bStart) ? cv1.StartPoint : cv1.EndPoint)).GetNormal();
            p += dir * offset;
            cv1.Extend(bStart, p);
          }
          catch (Autodesk.AutoCAD.Runtime.Exception ex)
          {
            ed.WriteMessage(ex.ToString());
          }
        }
      }
    }
  }
}

[Anonymous]

So I am running into an issue with the code, once I alter it to extend PAST the point, it refuses to extend that side at all.

                                    Curve ptLiveEnd = resCV3.ObjectId.Open(OpenMode.ForRead) as Curve;
                                    Point3dCollection ptss = new Point3dCollection();
                                    subCurv.IntersectWith(ptLiveEnd, Intersect.ExtendBoth, ptss, IntPtr.Zero, IntPtr.Zero);
                                    if (ptss.Count > 0)
                                    {
                                        Point3d p2 = ptss[0];
                                        Point3d pStart2 = subCurv.StartPoint;
                                        Point3d pEnd2 = ptLiveEnd.EndPoint;
                                        bool bStart2 = (p2.DistanceTo(pStart2) < p2.DistanceTo(pEnd2));
                                        double dist = Math.Min(p2.DistanceTo(pStart2), p2.DistanceTo(pEnd2));
                                        double offst = 24;
                                        for (int i = 1; i < ptss.Count; i++)
                                        {
                                            if (ptss[i].DistanceTo(pStart2) < dist)
                                            {
                                                p2 = ptss[i];
                                                bStart2 = true;
                                                dist = p2.DistanceTo(pStart2);
                                            }
                                            else if (ptss[i].DistanceTo(pEnd2) < dist)
                                            {
                                                p2 = ptss[i];
                                                bStart2 = false;
                                                dist = p2.DistanceTo(pEnd2);
                                            }
                                        }
                                        try
                                        {
                                            Vector3d dir = (p2 - ((bStart2) ? subCurv.StartPoint : subCurv.EndPoint)).GetNormal();
                                            p2 += dir*offst;
                                            subCurv.Extend(bStart2, p2);
                                        }
                                        catch (Autodesk.AutoCAD.Runtime.Exception exx)
                                        {
                                            acEd.WriteMessage(exx.ToString());
                                        }
                                    }

[Alexander.Rivilis]

I think it's time you learn how to use a debugger to see what wrong with your's code.

Look like you can not rewrite my code. Why you use:

Point3d pEnd2 = ptLiveEnd.EndPoint;

???

Maybe you have to use:

Point3d pEnd2 = subCurv.EndPoint;

???

[Anonymous]

Ah; ptLiveEnd is cv2, and subCurv is cv1 essentially, they aren't chosen, but pre-determined by earlier parts of the code.;

[Alexander.Rivilis]

---

@Anonymous wrote:

Ah; ptLiveEnd is cv2, and subCurv is cv1 essentially, they aren't chosen, but pre-determined by earlier parts of the code.;

---

Compare with my code.

[Anonymous]

You sir, are very patient and helpful.

I am, however, an idiot.

That fixed it xD

[Anonymous]

One last problem that I am running into. It works perfectly in all cases except for if the line to extend to is already the end point. How would I have it extend two feet past the line of extend even if it is already at that line.