Is there a way to get information on a selected Polyline segment
With Polyline.GetArcSegment[2d]At()/GetSegment[2d]At() method in conjunction with Polyline.GetSegmentType(), you can get the information you need.
@nshupeFMPE3 wrote:
You can use CTRL + Click on a segment of a polyline in order to highlight it. But is there any way to get information about that highlighted segment? Even just being able to get the length of that line segment could be useful.
What do you need this for? Are you using it as part of a program or just need to know the length? Once you have it selected as you noted, the Properties palette has all that info.
Ed
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Your question is quite vague: why you do not know which segment is the target while you are writing code? You should explain under what circumstance you need to determine the target segment. For example, when your code ask user to select polyline y calling Editor.GetEntity() method, which user required user to pick a polyline and returns a PromptEntityResult object (if the PromptStatus is PromptStatus.OK), which is not only includes an ObjectId of the selected entity/polyline, but also includes a property "PickedPoint", indicating where the user is picked. You can use the point to determine which segment of the polyline is picked. Note the point is the center of the mouse cursor, which is not necessarily exactly on the polyline. You need to call Polyline.GetClosestPoint() method to decide where exactly the segment is picked.
Again, if it is not your code to ask user to select a polyline, then you really need to explain VERY WELL your case as why/when/how a polyline is selected before you want to identify a segment of the polyline.
That might be a problem. A pline stores vertices, not segments. There are no 'properties' for a segment. You would have to calculate the length as a vector vertices(0)-vertices(1). If you wanted to store xdata, I think you have to do it at the entity level. I don't think you can attach it to a vertex. If the first segment is from vertex 0 to vertex 1, then you could attach xdata to the pline as a dotted pair ("0-1" . 1050).
Ed
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The code for getting segment index according to the point on curve/polyline could be much simple (not necessarily use less computer power to compute):
var index=Convert.ToInt32(Math.Floor(pline.GetParamterAtPoint(ptOnPolyline)));
Here's an example which works whatever the current UCS (PromptEntityResult.PickedPoint is returned in UCS coordinates) and whatever the current view (by using this overload of Curve.GetClosestPointTo which projects the curve onto the plane defined by the supplied Point3d and Vector3d).
public class Commands
{
[CommandMethod("TEST")]
public void Test()
{
var doc = Application.DocumentManager.MdiActiveDocument;
var db = doc.Database;
var ed = doc.Editor;
var options = new PromptEntityOptions("\nSelect a polyline segment: ");
options.SetRejectMessage("\nSelected object is not a polyline.");
options.AddAllowedClass(typeof(Polyline), true);
var result = ed.GetEntity(options);
if (result.Status != PromptStatus.OK)
return;
var id = result.ObjectId;
var pickedPoint = result.PickedPoint.TransformBy(ed.CurrentUserCoordinateSystem);
using (var tr = new OpenCloseTransaction())
{
var pline = (Polyline)tr.GetObject(id, OpenMode.ForRead);
using (var view = ed.GetCurrentView())
{
var pointOnPline = pline.GetClosestPointTo(pickedPoint, view.ViewDirection, false);
int index = (int)pline.GetParameterAtPoint(pointOnPline);
double GetArcLength(CircularArc2d arc) =>
arc.GetLength(arc.GetParameterOf(arc.StartPoint), arc.GetParameterOf(arc.EndPoint));
string message;
switch (pline.GetSegmentType(index))
{
case SegmentType.Line:
message = $"\nLine segment Index: {index} Length: {pline.GetLineSegment2dAt(index).Length:0.00}";
break;
case SegmentType.Arc:
message = $"\nArc segment Index: {index} Length: {GetArcLength(pline.GetArcSegment2dAt(index)):0.00}";
break;
default:
message = "\nInvalid segment";
break;
}
ed.WriteMessage(message);
}
tr.Commit();
}
}
