vb.net LEN Total

[Jozi68]

I need to write code to change the length of a line, almost like the LEN Total command. I have the line and the startpoint. Any ideas? It has to be in vb.net

[MSasu]

Can try the following approach:

• list the start and respectively end points;
  
• calculate line's angle from X axis;
  
• recalculate location of new end point using sine and cosine of angle and the desired length;
  
• update the end point attribute of line.

Done!

 

Can post for you the VBA code but I'm afraid that is quite different than VSTA one.

 

Regards,

[Jozi68]

Thanx msasu, I would appreciate the VBA code. I think I should be able to figure it out.

[MSasu]

Here it is (variables not declared):

 

LinePoint1st = [color=blue]theLineEntity[/color].StartPoint      'list extremities
LinePoint2nd = [color=blue]theLineEntity[/color].EndPoint

DeltaX = LinePoint2nd(0) - LinePoint1st(0)   'line size along axis
DeltaY = LinePoint2nd(1) - LinePoint1st(1)

If DeltaX = 0 Then                           'calculate angle from X axe (avoid zero division)
   Alfa = Atn(DeltaY / DeltaX)
Else
   If DeltaY > 0 Then
       Alfa = 0.5 * pi '90 degrees, positive
   Else
       Alfa = -0.5 * pi '90 degrees, negative
   End If
End If

NewDeltaX = [color=blue]NewLineLength[/color] * Cos(Alfa)        'new sizes along axis
NewDeltaY = [color=blue]NewLineLength[/color] * Sin(Alfa)

Set NewLinePoint2nd = LinePoint1st           'calculate new end point
NewLinePoint2nd(0) = NewLinePoint1st(0) + NewDeltaX
NewLinePoint2nd(1) = NewLinePoint1st(1) + NewDeltaX

theLineEntity.StartPoint = NewLinePoint2nd   'update line entity

Regards,

[MSasu]

Also, can get line’s orientation directly from the entity:

 

Alfa = [color=blue]theLineEntity[/color].Angle

 

Regards,

[Jozi68]

Thanx, I got it to work

[MSasu]

Sound good! You're welcome!

[gile]

Hi,

 

IMO, writing .NET from VBA coding isn't a good way to learn .NET.

.NET provides much more APIs than COM to deal with geometry issues (i.e. using 3d vectors rather than 2d angles).

 

Here's a little sample (C#).

It contains a function (LineTotalLength) which changes the total length of a line on the picked side (requieres the line ObjectId, the picked point and the length) and a 'Test' command.

 

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

namespace LengthenSample
{
   public class Class1
   {
       [CommandMethod("Test")]
       public void Test()
       {
           Editor ed = Application.DocumentManager.MdiActiveDocument.Editor;
           PromptEntityOptions peo = new PromptEntityOptions("\nSelect a line: ");
           peo.SetRejectMessage("Selected entitiy is not a line");
           peo.AddAllowedClass(typeof(Line), true);
           PromptEntityResult per = ed.GetEntity(peo);
           if (per.Status != PromptStatus.OK)
               return;
           PromptDistanceOptions pdo = new PromptDistanceOptions("\nTotal length: ");
           pdo.AllowNegative = false;
           pdo.AllowZero = false;
           PromptDoubleResult pdr = ed.GetDistance(pdo);
           if (pdr.Status == PromptStatus.OK)
               LineTotalLength(per.ObjectId, per.PickedPoint.TransformBy(ed.CurrentUserCoordinateSystem), pdr.Value);
       }

       private void LineTotalLength(ObjectId id, Point3d pt, double len)
       {
           Database db = Application.DocumentManager.MdiActiveDocument.Database;
           using (Transaction tr = db.TransactionManager.StartTransaction())
           {
               Line l = (Line)tr.GetObject(id, OpenMode.ForWrite);
               Point3d sPt = l.StartPoint;
               Point3d ePt = l.EndPoint;
               if (pt.DistanceTo(sPt) < pt.DistanceTo(ePt))
               {
                   Vector3d vec = ePt.GetVectorTo(sPt).GetNormal();
                   l.StartPoint = ePt + vec * len;
               }
               else
               {
                   Vector3d vec = sPt.GetVectorTo(ePt).GetNormal();
                   l.EndPoint = sPt + vec * len;
               }
               tr.Commit();
           }
       }
   }
}