[vtkusers] Re: MIP...

[Eduardo Kortright]

Hi Marcelo,

Varying opacity does not make much sense with a MIP.  I would specify
maximum opacity for all data values:

    vtkPieceWiseFunction opacity
        opacity AddSegment 0 1.0 255 1.0

(assuming your volume is in UnsignedChars, and you're using Tcl).

For color, you could use anything (even all white); if you want to use
different colors for different scalar values, you might try a transfer
function similar to the standard lookup table provided by vtkLookupTable,
which goes through the HSV color space from red to blue:

    vtkColorTransferFunction color
        color SetColorSpaceToRGB
        color AddRGBPoint 0 1 0 0
        color AddRGBPoint 64 1 1 0
        color AddRGBPoint 128 0 1 0
        color AddRGBPoint 192 0 1 1
        color AddRGBPoint 255 0 0 1

If you want a color transfer function that results in more physiologically
accurate colors, you would probably have to design it specifically for your
data.  (Does anyone know if there are there standard ways of building such
transfer functions?)

Hope this helps.

--
Eduardo Kortright                         Department of Computer Science
eduardo at cs.uno.edu                        University of New Orleans
Phone: (504) 280-6626                     Lakefront Campus
Fax:   (504) 280-7228                     New Orleans, LA 70148




> Message: 11
> Date: Thu, 05 Dec 2002 14:18:02 +0000
> From: Marcelo <amati at cenpra.gov.br>
> To: vtkusers at public.kitware.com
> Subject: [vtkusers] MIP...
>
> Hi,
>
>         I'm trying to use the volume rendering method MIP (in a medical
> volume) and I can't see anything. Does somebody know an opacity transfer
> function and a color transfer function that allow a good visualization?
>
>         Thank you.
>
>         Marcelo
>