[vtkusers] A bug in Above/BelowRangeColor mapping?

[Mathieu Westphal]

Hi Marcin,

Regarding ParaView, you may want to post on our discourse instead
https://discourse.paraview.org/


Mathieu Westphal


On Mon, Oct 15, 2018 at 9:38 AM marcin.krotkiewski <
marcin.krotkiewski at gmail.com> wrote:

> Hi,
>
> I think the behavior of UseBelowRangeColor in both VTK 8.1.1, and
> Parview 5.5 is wrong. As an example, I load a surface into Paraview,
> rescale the color range to point data (elevation in this case, fig.
> paraview.png), and enable the 'Use Below Range Color' checkbox. What you
> see is that part of the surface are colored with black (fig.
> paraview_wrong.png), although they are in fact within the automatically
> computed value range. So they should get the usual color from the lookup
> table.
>
> I also observe wrong behavior when I color the surface by a constant
> value. In VTK, I set lower/upper bound on data values in vtkLookupTable
> to be the same. Say, my point data has value 50. I set the lookup table
> range to [60,60] and turn on Above/Below range color. Figure
> constant_wrong.png shows that my surface is colored with the in-range
> color, although it is below range. To get a correct coloring I need to
> spread the range a little bit, e.g., [60,61] (constant_below.png), or
> [40, 41] (constant_above.png). But even in this case we go back to the
> first problem: for point values that are on the edge of the range VTK
> uses out-of-range color (range [50,51], constant_extreme.png).
>
> So the question is - is this behavior intended, and if so - how should I
> organize my color mapping and data ranges to get the expected behavior?
>
> Regards,
>
> Marcin Krotkiewski
>
>
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