Append Nurbs Curve to PolyCurve()

Rhino Developer
1

I can see that PolyCurve() class has an Append() method. My question is does it only accept Line, Curve and Arc classes? I am trying to construct a PolyCurve from Lines, arcs and nurbscurves. Does anyone have an example of appending a Nurbs Curve to PolyCurve? I keep getting False as a result.

2

Well, a Rhino.Geometry.Curve is an abstract class, and a Rhino.Geometry.NurbsCurve inherits from Curve. So (basically) you can append any kind of curve.

Here is a cheap sample of how to build a polycurve:

protected override Result RunCommand(RhinoDoc doc, RunMode mode)
{
  var go = new GetObject();
  go.SetCommandPrompt("Select polycurve");
  go.GeometryFilter = ObjectType.Curve;
  go.SubObjectSelect = false;
  go.Get();
  if (go.CommandResult() != Result.Success)
    return go.CommandResult();

  var crv = go.Object(0).Curve();
  if (null == crv)
    return Result.Failure;

  var polycrv = crv as PolyCurve;
  if (null == polycrv)
  {
    RhinoApp.WriteLine("Not a polycurve");
    return Result.Failure;
  }

  var pieces = polycrv.Explode();

  var new_polycrv = new PolyCurve();
  foreach (var piece in pieces)
    new_polycrv.Append(piece);

  if (new_polycrv.IsValid)
  {
    doc.Objects.AddCurve(new_polycrv);
    doc.Views.Redraw();
  }

  return Result.Success;
}
3

Hi Dale,

Yes, this is very similar to what I have been trying to implement. What would be the reason that a PolyCurve would be invalid? After I append all my pieces to it, I checked it for IsValid and it returns False. Of course I am not building it by exploding and rebuilding it like you are showing but It was very much a valid curve in the past/other software (Dynamo).

4

This might help you figure out where the problem in your polycurve is:

string log;
if (new_polycrv.IsValidWithLog(out log))
{
  doc.Objects.AddCurve(new_polycrv);
  doc.Views.Redraw();
}
else
{
  Rhino.UI.Dialogs.ShowTextDialog(log, EnglishName);
}
5

I should add that the Append member doesn’t do a whole lot. So if you have a pile of unorganized and/or unorienteded curves, best to use Curve.JoinCurves.

~ D

6

Will do, thank you,