# Diverging Log Lookup Table
**URL:** https://discourse.vtk.org/t/diverging-log-lookup-table/10216
**Category:** Support
**Created:** [December 15, 2022, 4:37pm UTC](https://discourse.vtk.org/t/diverging-log-lookup-table/10216 "2022-12-15T16:37:26Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@BlueKnight7](https://discourse.vtk.org/u/BlueKnight7)
#### Post date: [December 15, 2022, 4:37pm UTC](https://discourse.vtk.org/t/diverging-log-lookup-table/10216/1 "2022-12-15T16:37:26Z")
This question is prompted from the MakeLUT function in the DisplacementPlot example:
[https://kitware.github.io/vtk-examples/site/Cxx/VisualizationAlgorithms/DisplacementPlot/](https://kitware.github.io/vtk-examples/site/Cxx/VisualizationAlgorithms/DisplacementPlot/)
The MakeLUT function shows how to generate LUT’s with diverging color schemes as described by Kenneth Moreland on his website (given on the example’s webpage).
Is there a way to create these diverging LUT’s using a **vtkLogLookupTable**?
I know that for scalars I could always take the log of the scalar and use a linear vtkLogLookupTable.
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### Author:  [@Paulo\_Carvalho](https://discourse.vtk.org/u/Paulo_Carvalho)
#### Post date: [December 20, 2022, 12:55pm UTC](https://discourse.vtk.org/t/diverging-log-lookup-table/10216/2 "2022-12-20T12:55:04Z")
Hi,
What are you getting? An error? Wrong colors or no rendering at all?
regards,
Paulo
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### Author:  [@BlueKnight7](https://discourse.vtk.org/u/BlueKnight7)
#### Post date: [December 20, 2022, 2:49pm UTC](https://discourse.vtk.org/t/diverging-log-lookup-table/10216/3 "2022-12-20T14:49:44Z")
Hi Paulo,
I didn’t try it – yet. In looking at the code in MakeLUT, it didn’t appear that a log table would work.
I’m curious if anyone has diverging log tables working.
BK
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### Author:  [@Paulo\_Carvalho](https://discourse.vtk.org/u/Paulo_Carvalho)
#### Post date: [December 20, 2022, 3:03pm UTC](https://discourse.vtk.org/t/diverging-log-lookup-table/10216/4 "2022-12-20T15:03:06Z")
Hello,
Well, give it a shot and see what happens. 🙂
best,
Paulo
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### Author:  [@BlueKnight7](https://discourse.vtk.org/u/BlueKnight7)
#### Post date: [December 20, 2022, 3:58pm UTC](https://discourse.vtk.org/t/diverging-log-lookup-table/10216/5 "2022-12-20T15:58:15Z")
Will do. I should have tried it, but have been juggling too much – still am.
BK
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### Author:  [@BlueKnight7](https://discourse.vtk.org/u/BlueKnight7)
#### Post date: [December 21, 2022, 11:13pm UTC](https://discourse.vtk.org/t/diverging-log-lookup-table/10216/6 "2022-12-21T23:13:14Z")
Well, I tweaked the displacement example that I mentioned before and the log LUT worked. At first there was the error:
vtkLookupTable.cxx:160 ERR| vtkLogLookupTable (0x1ee46f0): Bad table range for log scale: [-1, 1]
When I changed the range in the example, it worked and there was no error message. I need to check this on something more complex in the future. But, at least there is something.
BK
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### Author:  [@Paulo\_Carvalho](https://discourse.vtk.org/u/Paulo_Carvalho)
#### Post date: [December 22, 2022, 1:16pm UTC](https://discourse.vtk.org/t/diverging-log-lookup-table/10216/7 "2022-12-22T13:16:36Z")
> [@BlueKnight7](#):
>
> Bad table range for log scale: [-1, 1]
The log function is undefied for negative arguments, thus the error.
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### Author:  [@BlueKnight7](https://discourse.vtk.org/u/BlueKnight7)
#### Post date: [December 22, 2022, 2:12pm UTC](https://discourse.vtk.org/t/diverging-log-lookup-table/10216/8 "2022-12-22T14:12:30Z")
Yes, I knew that. I just didn’t see that the example was setting a definite range.