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

[Mark Asbach]

Hi folks,

> We would like a solution for this as well for colouring finite element 
> models.

Okay, so we are indeed a couple of people now using vtk for FE 
visualization? That's a fine thing.

>> calculations. So OpenGL will shade red to green producing=20
>> yellow along the way which is not in your lookup table!
> Yes, right.. That is the problem!
>
> BUT.. there must be a solution on that one! Are we the only
> one needing this ? ;)

As Rainer already pointed out, using a texture map is the only solution 
that works for true colour and complex shader models. Our own FE 
visualizer works that way but we're also moving to VTK and need to keep 
the functionality. In addition to Rainers comment I would like to ask 
the VTK team if they could enable 1D textures soon and probably 
integrate the functionality into the usual rendering process as an 
(automatic?) feature of vtkLookupTable and the vtkActors / 
vtkRenderers.

You can have a look at our code at

	http://imoose.sourceforge.net

or look into a posting that explains 1D textures for vertex colouring 
in a compact form and with source code

	http://www.geocrawler.com/archives/3/1291/2000/7/50/3977584

That was our information source, too. Unfortunately I don't have the 
time to implement this in VTK at the moment (new job) ... :-/

Good luck,

Mark