[vtkusers] color mapping

[Frédéric Speisser]

Thank you all,

Finally, I found a way to achieve what I wanted to do in overriding 
function /MapScalars/ of /vtkLookupTable/, so i'm now be able to manage 
custom color mapping.

Kind regards,
Frédéric

Le 04/12/2012 10:27, Johannes Strecha a écrit :
> 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 
> <mailto: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>
>     [mailto: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 <mailto: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 <mailto: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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