[vtkusers] Glyph coloring

[Gib Bogle]

It turns out there was a difference between what I was doing and the wiki 
example code, one of those seemingly insignificant details that are actually 
important.

I had
   glypher->SetScaleFactor(1.0);
and the wiki code has
   glypher->ScalingOff();
With that change it works (although I don't know why).

I have a final (I hope!) question.  I now want to selectively change the color 
of glyphs.  I know how to change the position of the point indexed by idx:
   points->SetPoint(idx,x,y,z);
   glypher->Modified();

Presumably something very similar is needed to change the color of this glyph, 
but I don't know how to access the array that holds the colors, which was 
initialized with:
   input->GetPointData()->SetScalars(colors);

Can someone help me over this last hurdle?


On 26/11/2010 12:42 p.m., Gib Bogle wrote:
> I've been trying to follow David Gobbi's suggestion about coloring the glyphs
> that I am now using to render my squares with. The hints he provided were not
> enough for me to get it working, so I hunted around and found the wiki example
> http://www.itk.org/Wiki/VTK/Examples/Cxx/Visualization/ColorGlyphs
> This works fine, so I thought I could just follow the same path. It doesn't work
> for me, and I'm guessing that it's because I'm using a vtkPolyData that contains
> both vtkPoints and vtkCellArray. David advised me to use
> input->GetPointData()->AddArray(...)
> but I couldn't see how to implement this. My code is shown below. What am I
> missing? (This code doesn't display the squares at all, unless I comment out
> input->GetPointData()->SetScalars(colors).)
> I apologize for the ignorance I'm displaying - I don't understand why it's
> necessary to use the vtkCellArray, for example.
>
> points = vtkSmartPointer<vtkPoints>::New();
> vtkSmartPointer<vtkCellArray> dummycells = vtkSmartPointer<vtkCellArray>::New();
> points->SetNumberOfPoints(npos); // number of squares
> dummycells->InsertNextCell(npos);
> colors = vtkSmartPointer<vtkUnsignedCharArray>::New();
> colors->SetName("colors");
> colors->SetNumberOfComponents(3);
> unsigned char g[3] = {0,255,0};
> for (int ipos=0; ipos<npos; ipos++) {
> points->SetPoint(ipos, x, y, z);
> dummycells->InsertCellPoint(ipos);
> colors->InsertNextTupleValue(g);
> }
> input = vtkSmartPointer<vtkPolyData>::New();
> input->SetPoints(points);
> input->SetVerts(dummycells);
> input->GetPointData()->SetScalars(colors);
> glypher = vtkSmartPointer<vtkGlyph3D>::New();
> glypher->SetInput(input);
> glypher->SetSource(polygonPolyData);
> glypher->SetScaleFactor(1.0);
> glypher->SetColorModeToColorByScalar();
> // glypher->SetInputArrayToProcess(3, 0, 0, 0, "colors");
> glypher->Update();
> squareMapper = vtkPolyDataMapper::New();
> squareMapper->SetInputConnection(glypher->GetOutputPort());
> glactor = vtkActor::New();
> glactor->SetMapper(squareMapper);
> glactor->GetProperty()->SetAmbient(0.5);
> glactor->GetProperty()->SetDiffuse(0.2);
> glactor->GetProperty()->SetSpecular(0.5);
> ren->AddActor(glactor);
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