[vtkusers] Filter to merge several lines into a single polyline?

[Jean-Dominique Barnichon]

Hello,

As a result of applying a vtkCutter filter to a 3D surface (see code snippet
below), I obtain a vtkPolyData object that is made of :
 - a set of points,
 - a set of lines (7 in the example below, see ouput below).

You can notice that output lines share end points, i.e. they could 'easily'
all be converted into a single polyline (in the exmaple shown below, this
could be done starting backward from the last line, but I don't known this
can always be done this way).

All I need is converting this set of 'jointive' lines into a single
polyline.
Is there any filter that can do that? Or do I have to write one by myself?

Any answer/hint is welcome.
Note that applying vtkCleanPolyData is pointless here as there are already
no duplicate points.

Jean-Do


code snippet
	//Define cutting plane
	vtkPlane* plane = vtkPlane::New();
	plane->SetOrigin(300., 500., 0);
	plane->SetNormal(-1, -1, 0);

	//Generate cut lines
	vtkCutter* cutEdges = vtkCutter::New();
	cutEdges->SetInput(Normals->GetOutput());
	cutEdges->SetCutFunction(plane);

	//Forms lines from cutter
	vtkStripper* cutStrips = vtkStripper::New();
	cutStrips->SetInput(cutEdges->GetOutput());
	cutStrips->Update();

	//Defines polygons as polyline
	vtkPolyData* LinePoly = vtkPolyData::New();
	LinePoly->SetPoints((cutStrips->GetOutput())->GetPoints());
	LinePoly->SetLines((cutStrips->GetOutput())->GetLines());

	//Write PolyData to file
	vtkPolyDataWriter* wr = vtkPolyDataWriter::New();
	wr->SetFileName("Line4.vtk");
	wr->SetInput(LinePoly);
	wr->Write();

Output of the vtkPolyDataWriter (file Line4.vtk)
# vtk DataFile Version 3.0
vtk output
ASCII
DATASET POLYDATA
POINTS 28 float
252.329 547.171 500 235.668 563.832 500 314.825 484.675 549.214
305.908 493.592 553.277 224.208 575.292 500 223.112 576.388 500
342.103 457.397 590.352 339.985 459.515 587.917 446.203 353.297 737.623
441.629 357.871 700 294.445 505.055 542.116 343.253 456.247 592.317
415.885 383.615 664.838 409.217 390.283 664.838 350.938 448.562 600
426.08 373.42 670.902 439.236 360.264 700 492.288 307.212 866.422
482.154 317.346 884.873 458.735 340.765 779.183 451.048 348.452 750.164
479.711 319.789 887.034 463.563 335.937 800 512.234 287.266 900
510.437 289.063 900 496.357 303.143 851.732 502.247 297.253 829.042
519.514 279.986 900
LINES 7 41
4 0 1 4 5
4 2 3 10 0
3 6 7 2
9 8 9 16 15 12 13 14 11 6
7 17 18 21 22 19 20 8
5 23 24 26 25 17
2 27 23

CELL_DATA 7
POINT_DATA 28