[vtkusers] vtkLookupTable does not handle NaN values with Log10 scale

[Elvis Stansvik]

2016-09-21 11:25 GMT+02:00 Miorelli, Federico <Federico.Miorelli at cgg.com>:
> Dear All,
>
>
>
> It seems like vtkLookupTable does not handle correclty NaN values when the
> Log10 scale is used.
>
> In this case, all the NaNs in the input are not mapped to NanColor but to
> the minimum range color.

Sorry to hijack the thread, but since it's related and I've been
meaning to ask: How is vtkPiecewiseFunction supposed to handle NaN
values? It does not have a NanColor setting like vtkLookupTable and
vtkColorTransferFunction has. I guess if I specify a
vtkPiecewiseFunction as scalar opacity transfer function during volume
rendering, I better ensure I have no NaN values (i.e. filter them
out)?

Elvis

>
>
>
> Unless there is a reason for this, I believe the bug is in
> vtkLookupTable::vtkApplyLogScale().
>
>
>
> Here is a patch that might fix it (VTK 6.3.0)
>
>
>
>
>
> --- old/vtkLookupTable.cxx    Wed Jul 13 15:11:08 2016
>
> +++ new/vtkLookupTable.cxx    Wed Sep 21 10:54:24 2016
>
> @@ -358,6 +358,11 @@
>
> inline double vtkApplyLogScale(double v, const double range[2],
>
>                                 const double logRange[2])
>
> {
>
> +   if (vtkMath::IsNan(v))
>
> +     {
>
> +     return v;
>
> +     }
>
> +
>
>    // is the range set for negative numbers?
>
>    if (range[0] < 0)
>
>      {
>
>
>
>
>
> Regards,
>
> Federico
>
>
>
>
>
>
>
> ______ ______ ______
>
> Federico Miorelli
>
>
>
> Senior R&D Geophysicist
>
> Subsurface Imaging - General Geophysics Italy
>
>
>
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