166 Posts
9 Kudos
Registered: ‎06-16-2008
Post 1 of 3

Get Point Along Curve

287 Views, 2 Replies
01-22-2013 01:03 AM

Hey All,


I am developing a tool that will allow a user to select a curve, and dump out the points at given intervals along said curve.


This works well for 2D objects.


If I have a line from 0,0,0 to 10,0,1


it outpus

0, 0, 0

0.9950, 0, 0.0995

1.9901, 0, 0.1990


What I want it to output is the point at the interval (2D plane, with the elevation)

0, 0, 0

1, 0, 0.1

2, 0, 0.2



Is there a way a function I can use that would allow this, or do I need to write my own function?


I hope that made sense.






1,464 Posts
277 Kudos
Registered: ‎04-09-2008
Post 2 of 3

Re: Get Point Along Curve

01-22-2013 02:21 AM in reply to: BrentBurgess1980

BrentBurgess1980 wrote:

Is there a way a function I can use that would allow this, or do I need to write my own function?

You have to write own function.

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*Expert Elite*
1,569 Posts
171 Kudos
Registered: ‎10-08-2008
Post 3 of 3

Re: Get Point Along Curve

01-23-2013 01:13 AM in reply to: BrentBurgess1980

Hi Brent

You can use virtual plane to get the points, see quick example,

Im using existing line for test but you can create LineSegment3d

or CircularArc3d for your polyline segments instead, but way would be the same:

        public void testLineDivisions()
            Document doc = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument;
            Database db = doc.Database;
            Editor ed = doc.Editor;
            PromptEntityOptions peo = new PromptEntityOptions("\nSelect a Line: ");
            peo.SetRejectMessage("Only a Line !");
            peo.AddAllowedClass(typeof(Line), false);
            PromptEntityResult per = ed.GetEntity(peo);
            if (per.Status != PromptStatus.OK) return;
            ObjectId lid = per.ObjectId;

            PromptDoubleOptions pdo = new PromptDoubleOptions("\nEnter step: ");
            pdo.AllowNone = true;
            pdo.UseDefaultValue = true;
            pdo.DefaultValue = 1.0;

            PromptDoubleResult res;
            res = ed.GetDouble(pdo);
            if (res.Status != PromptStatus.OK) return;
            double step = res.Value;

            ed.WriteMessage("\nStep entered:\t{0}\n", step);
            Point3d pt;
            Point3d tmp;
            using (Transaction tr = db.TransactionManager.StartOpenCloseTransaction())
                Entity ent = tr.GetObject(lid, OpenMode.ForWrite) as Entity;
                if (ent == null) return;
                Line ln = ent as Line;
                if (ln == null) return;
                Line3d lc = new Line3d(new Point3d(0, 0, 0), new Point3d(10, 0, 1));// current line
                Line3d lx = new Line3d(new Point3d(0, 0, 0), new Point3d(10, 0, 0));// line along x axis
                Plane plan = new Plane();
                int i = 0;
                for (double d = 0.1; d < 1.0; d += 0.1)
                    pt = lx.EvaluatePoint(d);
                    plan = new Plane(pt, Vector3d.XAxis);
                    tmp = plan.IntersectWith(lc)[0];// get intersection point between the line and virtual plane
                    ed.WriteMessage("\nPoint Number: {0}\tPoint: {1:f3}\n", i + 1, tmp);



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