[vtkusers] Re: Scalar color / LookupTable / Interpolation problem...

[Rainer Sabelka]

On Monday 03 May 2004 09:45, de Boer Ingo wrote:
> Hi,
>
> > To bypass OpenGL's  interpolation of colors I used a texture
> > map instead of a lookup table.
>
> It is not OpenGL's  interpolation of colors, it is VTK's
> interplation. I have it working in plain OpenGL. Look at
> my picture, I posted on friday.

Well, I'm not an expert in OpenGL, but I suspect you somehow told OpenGL to 
use your own lookup table (I just discovered the function glColorTable() in 
the OpenGL reference).

> I don't understand, why VTK does not use that. It makes
> our project senseless, when we have other values displayed.
> And looking at the replies, I am not the only one having
> trouble with that...

It seems that VTK uses its LookupTables only for determining the colors of the 
cell corners, but does not share this information with OpenGL, and therefore 
the interior of the cells is rendered by interpolation the RGBA values of the 
corners.

I have no idea how much effort it would be implementing such a feature  
(without breaking other stuff), but it would definitely be much appreciated.
Otherwise one has to stick with the work-around using texture maps, which is 
not very elegant (and maybe not as efficient).

cheers
-Rainer