[vtkusers] Update: Point number limit in vtkColorTransferFunction?

[Juan José Aja Fernández]

Again, sorry for the double posting:

Hi, Randall:

Curiously I'm using VTK5.0 compiled from source but the problem persists,
any ideas?

Thanks,

Juan.

On 2/10/06, Randall Hand <randall.hand at gmail.com> wrote:
>
> 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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