[vtkusers] Multi Dimensional Transfer Functions

[Randall Hand]

Unfortunately, VTK doesn't support what most people think of as
2-dimensional transfer functions in Volume Mapping.

Look in the vtkVolumeProperty and you'll see an option for
"IndependentComponents".  Using that, you can switch it through a few modes:
1) Map each scalar through it's own COlor & Opacity, and composite the
results
2) Map the first scalar through color, and the second scalar through OPacity
3) Use the first 3 scalars as RGB directly, and map the 4th scalar through
opacity.

Using the Array-Calculator, and probably some custom code, you should be
able to write code to generate a dataset with an RGBA (4-element) vector
field and method #3 to get what you want.

-- 
----------------------------------------
Randall Hand
Visualization Scientist
ERDC MSRC-ITL

On 7/24/07, tony marrero <tony.marrero at gmail.com> wrote:
>
> Hi guys,
>
> I am trying to implement a Multi Dimensional  transfer function design;
> similar to the work done by Kindlmann and Kniss et Al.
> I have not found anything useful in VTK to achieve this,  there was also a
> similar question posted a few years ago but there was no response, i dont
> know if now more people are aware of how this can be achieved.
>
> In VTK, i have found colour and opacity mappings that take their domain
> from *either* scalar values or gradient lookup tables, but not both
> simultaneously.
> I would like to have greater control over the rendering process , find a
> way to set colour and opacities to particular voxels of my choosing.
>
> Can someone kindly tell me how this can be achieved, or at least guide me
> in the correct direction.
>
> Thanks in advance,
>
> Tony Marrero
>
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