[vtkusers] color mapping

[Johannes Strecha]

Hello,

the vtk reference says that the vtkClipDataSet filter can be configured to
produce a second output, namely the part that was clipped away. A pipeline
with two clip-filters (for upper and lower bounds) that produce the clipped
part as second outputs and three mappers with suitably set color transfer
functions should produce the desired results.

However, I also think that one should be able to achieve this result with a
more simple setup.

Kind regards,
Johannes Strecha.


On Tue, Dec 4, 2012 at 9:57 AM, Deric Stone <dstone at medis.nl> wrote:

> Where are you using the lookup table? Can you use vtkColorTransferFunction
> or vtkDiscretizableColorTransferFunction instead? There you would be able
> to specify ranges.****
>
> ** **
>
> Note that GetColor(…) and MapValue(…) are not declared virtual in the
> vtkLookupTable class so cannot be overridden.****
>
> ** **
>
> Kind regards,****
>
> Deric Stone****
>
> ** **
>
> *From:* vtkusers-bounces at vtk.org [mailto:vtkusers-bounces at vtk.org] *On
> Behalf Of *Frédéric Speisser
> *Sent:* Monday, December 03, 2012 6:20 PM
> *To:* Johannes Strecha
> *Cc:* vtkusers at vtk.org
> *Subject:* Re: [vtkusers] color mapping****
>
> ** **
>
> Thank you Johannes for your answer,
>
> Yes, I know this algorithm, I also use it to filter data.
> But here my aim is not to filter data out-of-range but to keep these data
> visible but set in a custom color.
>
> Kind regards,
> Frédéric
>
> Le 03/12/2012 18:12, Johannes Strecha a écrit :****
>
> Hello,
>
> I can't give you a direct answer, but I think what you want can be done
> with the vtkClipDataSet filter (5.8). See the reference for details. I
> assume that adjusting the lookup table would work faster, though.
>
> When trying to realize a "filled contour plot" by adjusting the lookup
> table (to a series of steps) I experienced that some interpolation was
> performed nonetheless and I ended up with blurred filled contours. Maybe
> this would also happen in your case.
>
> Kind regards,
> Johannes Strecha.****
>
> ** **
>
> On Mon, Dec 3, 2012 at 5:31 PM, Frédéric Speisser <speisser at kappaeng.com>
> wrote:****
>
> Hi all,
>
>
> I'm using *vtkLookupTable::SetTableRange* to remap colors of a LUT to a
> custom range of a given scalar values.
>
> This works great but per default and as explained in API documentation :
> *Scalar values less than minimum range value are clamped to minimum range
> value. Scalar values greater than maximum range value are clamped to
> maximum range value.
> *So values out of range are displayed in minimum range value color (for
> those under custom range) and in maximum range value color (for those over
> custom range).
> I would like to display out-of-range values in a custom color, so that for
> example all values under and over custom range are displayed in black.
> I began to write a class *MyVtkLookupTable* which inherits from *vtkLookupTable
> *and i tried to override *GetColor(double v, double rgb[3])* and *MapValue(double
> v)* to be able to override color displayed but it seems not to work.
> Is it possible to do that by overriding vtk classes ? If yes, which
> method/classes should I override ?
>
> Any clues are wellcome, thank you,
>
>
>
> Frédéric ****
>
>
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