[vtkusers] Best way to visualize a RGB Volume?

[Sankhesh Jhaveri]

Hi Ludwig,

Just so I understand, you’d like to be able to pass the RGB volume through
a color lookup table too?

IMHO, if you have a RGB volume, adding a fourth component for opacity and
setting an opacity function with IndependentComponentsOff is the best
method.

*Note* that with two dependent components, the first component values are
used to lookup colors from the color transfer function i.e. the first
component can be as small as 1 byte (unsigned char).

Hth,
Sankhesh
​

On Mon, Jul 10, 2017 at 10:47 AM Willy <Wiggerl at linhuber.info> wrote:

> Hi,
>
> i want to visualize a RGB Volume and have a little problem. i do not think
> that there is a perfect solution, but maybe i am missing something.
>
> Here i my problem:
>
> There are three different Methods to visualize a RGB Volume:
> 1. Method: IndependentComponentsOn: three components (R,G,B), each with
> Colortransferfunction and opacityfunction
> 2. Method: IndependentComponentsOff: two components, first with
> Colortransferfunction and second with opacityfunction
> 3. Method: IndependentComponentsOff: four components, 1-3(R,G,B) with
> Colortransferfunction and fourth with opacityfunction
>
> Here are the disadvantages for each Method:
> 1. Method: It is not possible to create a colorTransferFunction or
> opacityFunction for the intensity value of a color(voxel), it is only
> possible to set these functions for each components seperate. This can lead
> to      falsified colors if the user changes these functions somehow (if
> you
> have the same color and opacity function for all components).
> 2. Method: the two components must have the same data type. the color
> component needs at least 3 byte, but there is no 3 byte type => 4 bytes for
> each component => 8 bytes per voxel => huge overhead.  Moreover the image
> quality for maximum intensity BlendMode is not as good as for the 1.
> Method.
> If you have (in the volume)  for example a green wall with value 250 and a
> red area behind it (for the current camera position) with value 200, you
> can't see the red area at all. In the first method the red area is
> displayed
> as yellow area (that is better).
> 3. Method: No colorFunction
>
> Is there a Method without disadvantages?
>
> MfG
> Ludwig
>
>
>
> --
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-- 
Sankhesh Jhaveri *Sr. Research & Development Engineer* | Kitware
<http://www.kitware.com/> | (518) 881-4417
​
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