[vtkusers] Polygon colouring

[David Thompson]

Hi Gib,

VTK's mappers treat unsigned char scalars as a special case because long ago colors had to be sent to the rendering API as 3-tuples of red, green, and blue unsigned char values. The VTK mappers are hardwired to deal with this case.

    David

On Oct 19, 2014, at 20:27, Gib Bogle <g.bogle at auckland.ac.nz> wrote:

> Thanks Bill.  Following David Gobbi's suggestion, I got something working in a similar way to the ColorCellsWithRGB example.  But I can't say I fully understand it.  Specifically, I don't see why this statement
> 
>  aPlane->GetOutput()->GetCellData()->SetScalars(cellData);
> or in my code
>  polygonPolyData->GetCellData()->SetScalars(colors);
> 
> sets the colours.  How is it that the vtkUnsignedCharArray is interpreted as providing colours?
> 
> Cheers
> Gib
> ________________________________________
> From: Bill Lorensen [bill.lorensen at gmail.com]
> Sent: Monday, 20 October 2014 12:39 a.m.
> To: Gib Bogle
> Cc: vtkusers at vtk.org
> Subject: Re: [vtkusers] Polygon colouring
> 
> Gib,
> 
> Here are a couple of examples:
> http://vtk.org/Wiki/VTK/Examples/Cxx/PolyData/ColorCellsWithRGB
> http://vtk.org/Wiki/VTK/Examples/Cxx/PolyData/ColorCells
> 
> Bill
> 
> On Sat, Oct 18, 2014 at 10:18 PM, Gib Bogle <g.bogle at auckland.ac.nz> wrote:
>> I'm rendering a shape using vtkPolyData, i.e. as a collection of polygons.
>> Is there a way to colour each polygon separately?
>> 
>> polygonPolyData = vtkSmartPointer<vtkPolyData>::New();
>> polygonPolyData->SetPoints(points);
>> polygonPolyData->SetPolys(polygons);
>> hexmapper = vtkSmartPointer<vtkPolyDataMapper>::New();
>> hexmapper->SetInput(polygonPolyData);
>> hexactor = vtkSmartPointer<vtkActor>::New();
>> hexactor->SetMapper(hexmapper);
>> 
>> ren->AddActor(hexactor);
>> 
>> 
>> Thanks
>> Gib
>> 
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> 
> 
> --
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