About the Curve2d.GetSplitCurves method in Geometry namespace

[stanmoong]

I'm looking at the API documentation, and it states that we need to pass in an "input parameter value at which curve is to be split", which is a double data type.

What does it mean by input parameter value?

Could anyone post a code snippet / pseudocode to illustrate how to use this?

Thanks.

[Hallex · Accepted solution]

I think you can use Curve to solve your task instead of Curve2d

See example

        [CommandMethod("PPB")]
        //for Discussion forum only
        static public void PlinePlineBreak()
        {
            Document doc = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument;
            Database db = doc.Database;
            Editor ed = doc.Editor;
            Transaction tr = db.TransactionManager.StartTransaction();
            using (tr)
            {
                PromptEntityOptions peo = new PromptEntityOptions("\nSelect First Polyline >>");
                peo.SetRejectMessage("\nSelect polyline only >>");
                peo.AddAllowedClass(typeof(Polyline), false);
                PromptEntityResult res;
                res = ed.GetEntity(peo);
                if (res.Status != PromptStatus.OK)
                    return;
                Entity ent = (Entity)tr.GetObject(res.ObjectId, OpenMode.ForRead);
                if (ent == null)
                    return;
                Polyline pline1 = (Polyline)ent as Polyline;
                if (pline1 == null) return;
                peo = new PromptEntityOptions("\nSelect Second Polyline >>");
                peo.SetRejectMessage("\nSelect polyline only >>");
                peo.AddAllowedClass(typeof(Polyline), false);
                res = ed.GetEntity(peo);
                if (res.Status != PromptStatus.OK)
                    return;
                ent = (Entity)tr.GetObject(res.ObjectId, OpenMode.ForRead);
                if (ent == null)
                    return;
                Polyline pline2 = (Polyline)ent as Polyline;
                if (pline2 == null) return;

                pline1.UpgradeOpen();

                pline2.UpgradeOpen();

                BlockTableRecord btr =
                    (BlockTableRecord)tr.GetObject(
                        db.CurrentSpaceId,
                        OpenMode.ForWrite,
                        false);

                List<double> pars1 = new List<double>();
                Curve fcurve = (Curve)tr.GetObject(pline1.ObjectId, OpenMode.ForRead);
                List<double> pars2 = new List<double>();
                Curve scurve = (Curve)tr.GetObject(pline2.ObjectId, OpenMode.ForRead);


                Point3dCollection iwpnts = new Point3dCollection();
                fcurve.IntersectWith(scurve, Intersect.OnBothOperands, iwpnts, 0, 0);
                foreach (Point3d p in iwpnts)
                {
                    pars1.Add(fcurve.GetParameterAtPoint(fcurve.GetClosestPointTo(p, false)));
                    pars2.Add(scurve.GetParameterAtPoint(scurve.GetClosestPointTo(p, false)));
                }

                if (pars1.Count == 0) return; if (pars2.Count == 0) return;

                pars1.Sort(); pars2.Sort();
                try
                {

                    foreach (Curve c in fcurve.GetSplitCurves(new DoubleCollection(pars1.ToArray())))
                    {
                        btr.AppendEntity(c);
                        tr.AddNewlyCreatedDBObject(c, true);
                    }
                    foreach (Curve c in scurve.GetSplitCurves(new DoubleCollection(pars2.ToArray())))
                    {
                        btr.AppendEntity(c);
                        tr.AddNewlyCreatedDBObject(c, true);
                    }
                    pline1.Erase(); pline2.Erase(); tr.Commit();

                }
                catch (Autodesk.AutoCAD.Runtime.Exception ex)
                {
                    Autodesk.AutoCAD.ApplicationServices.Application.ShowAlertDialog(ex.Message + "\n" + ex.StackTrace);
                }

            }
        }

~'J'~

[caddzone · Accepted solution]

A parameter value identifies a point on a curve. What the value means

exactly depends on the type of curve. With a database Curve, If you

know the point, and need the parameter you can pass the point to the

GetParameterAtPoint() method to get the parameter. There should also

be a corresponding method on the abstract curve classes.

[stanmoong]

Hi hallex,

Thanks for the code. I used the Autodesk.AutoCAD.DatabaseServices.Curve for splitting, was just wondering what is the difference between that and the one found in Autodesk.AutoCAD.Geometry.Curve2d class.

[stanmoong]

Hi caddzone,

So, if it's a Autodesk.AutoCAD.Geometry.Curve2d class, then what does the double value refer to?

[stanmoong]

Sorry, I misunderstood your reply. I checked in the API doc and found the Curve2d.GetParameterOf() method, which returns the parameter value.

It seems that I need to call this twice to get the line segments on each side of a polygon made of CompositeCurve2d, then form combine it to form new CompositeCurve2d.

Would it be advisable instead to use the Database namespace classes?

Basically, I need to pre-compute all the necessary vertices or line segments, before drawing using the Database namespace classes.