[vtkusers] Update: Point number limit in vtkColorTransferFunction?

[Randall Hand]

I ran into a similar goof a while back, reported here :
http://www.vtk.org/Bug/bug.php?op=show&bugid=2546&pos=3

That's since been fixed in VTK5.0. What version are you using?

On 2/10/06, Juan José Aja Fernández <juan.aja at gmail.com> wrote:
>
> Sorry for the double post, apparently the vtkusers mailing system only
> admits text only messages.
>
> Hi, everyone:
>
> I need to use Volume Rendering on an unstructured grid made out of voxels,
> the problem is that I have a lot of them (the grid minimum size is 50x50x50
> so at least 25000 voxels).
>
> I'm doing a truly horrible hack to try to color them:  generate a vtkPoint
> for each voxel in the grid by means of
>
> vtkDoubleArray *pts = ....
>
> for (i=0; i < numberOf Voxels;  i++)
>      pts->InsertNextValue(i);
>
> Then I assign pts to the vtkCellData of my grid:
>
> (grid->GetCellData())->SetScala rs(pts);
>
> And finally I populate the color transfer function.
> For example if I want to color my grid like a red-green chess board, I can
> do:
>
> for (i=0; i < numberOfVoxels; i++) {
>     if(i%2 == 0 && i != 0)
>         ctrans->AddRGBPoint(pts->GetValue(i), 1, 0, 0);
>     else ctrans->AddRGBPoint(pts->GetValue(i), 0, 1, 0);
> }
>
> The final result is very strange, the colors don't alternate the way they
> are supposed to (see the attached jpgs in the previous mail., the first one
> dimensions are: 5x5x5 and it looks good
> http://public.kitware.com/pipermail/vtkusers/attachments/20060210/d991c333/5x5x5.jpg
> the second one 19x19x19 but the checkered pattern dissapears:
> http://public.kitware.com/pipermail/vtkusers/attachments/20060210/d991c333/19x19x19.jpg
> ).
>
> Obviously I'm doing things wrong (the fact is that I'm somewhat new to vtk
> and I don't have the slightest idea of how to accomplish this), or is there
> a (short) limit in the number of points my transfer function can have?
>
> If not, how can this be accomplished?
>
> Thanks a lot,
> Juan
>
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>


--
Randall Hand
Visualization Scientist,
ERDC-MSRC Vicksburg, MS
Homepage: http://www.yeraze.com
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