[vtkusers] Re: MIP...

[Lisa S. Avila]

Hello,

I would recommend varying the opacity based on scalar value - a ramp from 0 
at the lowest value to 1.0 at the highest is typical. If you have constant 
1.0 opacity and constant white color you will render a solid white cube - 
not very interesting! :-)

Lisa


At 02:56 PM 12/5/2002, Eduardo Kortright wrote:
>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
> >
>
>_______________________________________________
>This is the private VTK discussion list.
>Please keep messages on-topic. Check the FAQ at: 
><http://public.kitware.com/cgi-bin/vtkfaq>
>Follow this link to subscribe/unsubscribe:
>http://public.kitware.com/mailman/listinfo/vtkusers