[vtkusers] How to set colors for contour edges?

[Vladimir Dudnik]

Well, seems I've found out how to set different colors to contour edges
http://vtk.1045678.n5.nabble.com/file/n5490071/vtk_color_lines_1.png 

but still have questions.

So, what I did is

1. create unsigned char array of colors I want to use (number of entries for
this array is number of points/edges in my data set
2. construct vtkPolyData object from points in my data set
3. assign array of colors to the cell data scalars
4. render this

The questions are:
I see the different results depending on how I construct the PolyData
object. If it is like this:
---------
  // r0 is array of nPoints point coordinates that form closed contour

  // create vtkPoints for rectangular contour
  vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();
  for(int i = 0; i < nPoints; i++)
    points->InsertNextPoint(r0[i].x, r0[i].y, 0.0);

  // connect polyline's point ids
  vtkSmartPointer<vtkPolyLine> polyline =
vtkSmartPointer<vtkPolyLine>::New();
  for(vtkIdType i = 0; i < nPoints; i++)
  {
    polyline->GetPointIds()->InsertNextId(i);
  }
  // close contour
  polyline->GetPointIds()->InsertNextId(0);

  // create cell array for polyline
  vtkSmartPointer<vtkCellArray> polylines =
vtkSmartPointer<vtkCellArray>::New();
  polylines->InsertNextCell(polyline);

  // create cell array for edges
  vtkSmartPointer<vtkCellArray> edges =
vtkSmartPointer<vtkCellArray>::New();

  // connect edge's point ids
  for(vtkIdType i = 0; i < nPoints; i++)
  {
    vtkSmartPointer<vtkLine> edge = vtkSmartPointer<vtkLine>::New();
    edge->GetPointIds()->SetId(0, i);
    edge->GetPointIds()->SetId(1, (i+1) % nPoints);
    edges->InsertNextCell(edge);
  }

  // create polydata obj
  vtkSmartPointer<vtkPolyData> data = vtkSmartPointer<vtkPolyData>::New();
  data->SetPoints(points);
  data->SetLines(edges);
  data->SetVerts(polylines);

  // set edges color
  data->GetCellData()->SetScalars(edgeColors);
------
then I got result shown on the screenshot above.

But if I construct PolyData as following:
------
  // create cell array for edges
  vtkSmartPointer<vtkCellArray> edges =
vtkSmartPointer<vtkCellArray>::New();

  // create cell array for vertexes
  vtkSmartPointer<vtkCellArray> vertexes =
vtkSmartPointer<vtkCellArray>::New();

  // connect edge's and vertexes point ids
  for(vtkIdType i = 0; i < nPoints; i++)
  {
    vtkSmartPointer<vtkLine> edge = vtkSmartPointer<vtkLine>::New();
    edge->GetPointIds()->SetId(0, i);
    edge->GetPointIds()->SetId(1, (i+1) % nPoints);
    edges->InsertNextCell(edge);

    vtkSmartPointer<vtkVertex> vertex = vtkSmartPointer<vtkVertex>::New();
    vertex->GetPointIds()->SetId(0, i);
    vertexes->InsertNextCell(vertex);
  }

  // create polydata obj
  vtkSmartPointer<vtkPolyData> data = vtkSmartPointer<vtkPolyData>::New();
  data->SetPoints(points);
  data->SetVerts(vertexes);
  data->SetLines(edges);

  data->GetCellData()->SetScalars(edgeColors);
------
I've got result like this
http://vtk.1045678.n5.nabble.com/file/n5490071/vtk_color_lines_2.png 

so why I can't use vtkCellArray for list of vertexes? From the other hand,
how it is possible that vertexes can be described by vtkPolyLine object?


And finally, is it possible to control the color of points independently
from color of lines?
When I tried to call data->GetPointData()->SetScalars(vertexColors) in
addition to data->GetCellData()->SetScalars() I've got result like this
http://vtk.1045678.n5.nabble.com/file/n5490071/vtk_color_lines_3.png 

seems setting scalars to PointData takes precedence over setting scalars for
CellData. Also, the strange thing is why there gradually change in color
over lines?

The compilable example of code (for the first described result) is attached
http://vtk.1045678.n5.nabble.com/file/n5490071/vtk_polyline_colors.cxx
vtk_polyline_colors.cxx 
 
what I'm doing wrong here?

Regards,
  Vladimir



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