Convert CIRCLE to Polyline

[Anonymous]

Hi Folks,

could you please help me anyone to convert circle to Polyline. I need C# Code to complete this action?

Regards

Alex Andrews.

[ralph.pyka]

This worked very well.  Thank you for sharing a nice solution.

[jbrissonHSYRW]

This is what I've done and it has worked very well for me.  I've needed it for adding wipeouts behind circular blocks.

[Chris_Rose47VDB]

Everytime I click on this link it takes me back to the forum main page. Where can I find the actual lsp?

[pendean]

---

@Chris_Rose47VDB wrote:

Everytime I click on this link it takes me back to the forum main page. Where can I find the actual lsp?

---

Actual LISP was posted a few replies later 

https://forums.autodesk.com/t5/visual-lisp-autolisp-and-general/convert-circle-to-polyline/m-p/89959...

[Kent1Cooper]

---

@pendean wrote:.....

Actual LISP was posted a few replies later 

---

Thanks for the referral.  I've changed the link in the earlier Message to go there.

This site has lots of broken links like that now....

[mehrdad.design9]

The easiest way is instead of drawing a circle, draw a polygon with 1000 sides. In CAD it looks like a circle. Then it will be a polyline and for example you can change the globe width of it easily.

[Sea-Haven]

"draw a polygon with 1000 sides" for me that is not easiest. adds 1000 values to your dwg. It would be easier to just draw a pline using the ARC option and draw 2 arcs, similar to the donut command.

(command "pLINE"  p2 "w" 0.0 0.0 "a" "-180" "l" p5 "a"......     )

[Kent1Cooper]

[Don't lose sight of the original question, which is not about drawing a circular Polyline, but rather about converting an already-drawn Circle into one.]

[_gile]

Here's a C# method which creates a polyline matching a circle. It works whatever the circle plane.

public static Polyline CircleToPolyline(Circle circle)
{
    var normal = circle.Normal;
    var plane = new Plane(Point3d.Origin, circle.Normal);
    var center2d = circle.Center.Convert2d(plane);
    var pt1 = center2d + Vector2d.XAxis * circle.Radius;
    var pt2 = center2d - Vector2d.XAxis * circle.Radius;
    var pline = new Polyline(2);
    pline.AddVertexAt(0, pt1, 1.0, 0.0, 0.0);
    pline.AddVertexAt(1, pt2, 1.0, 0.0, 0.0);
    pline.Closed = true;
    pline.Normal = normal;
    pline.Elevation = circle.Center.TransformBy(Matrix3d.WorldToPlane(plane)).Z; ;
    return pline;
}

An equivalent LISP routine:

(defun circle2pline (circle / elst normal center vector)
  (if
    (and
      (setq elst (entget circle))
      (= (cdr (assoc 0 elst)) "CIRCLE")
      (setq normal (cdr (assoc 210 elst)))
      (setq center (cdr (assoc 10 elst)))
      (setq vector (list (cdr (assoc 40 elst)) 0.))
    )
     (entmakex
       (list
	 (cons 0 "LWPOLYLINE")
	 (cons 100 "AcDbEntity")
	 (cons 100 "AcDbPolyline")
	 (cons 90 2)
	 (cons 70 1)
	 (cons 38 (caddr center))
	 (cons 10 (mapcar '+ center vector))
	 (cons 42 1.)
	 (cons 10 (mapcar '- center vector))
	 (cons 42 1.)
	 (cons 210 normal)
       )
     )
  )
)