# resliceMapper.setLookupTable is not a function
**URL:** https://discourse.vtk.org/t/reslicemapper-setlookuptable-is-not-a-function/8003
**Category:** Web
**Created:** [March 7, 2022, 1:19pm UTC](https://discourse.vtk.org/t/reslicemapper-setlookuptable-is-not-a-function/8003 "2022-03-07T13:19:07Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@dexter](https://discourse.vtk.org/u/dexter)
#### Post date: [March 7, 2022, 1:19pm UTC](https://discourse.vtk.org/t/reslicemapper-setlookuptable-is-not-a-function/8003/1 "2022-03-07T13:19:07Z")
Hey, how to set the Lookup Table for a resliceActor (`vtkImageSlice`)?
Because we can use `setLookupTable` method for a `vtkMapper` object but not for `vtkImageMapper`.
I need to set the LookupTable to make the black zone in the resliceActor transparent, is there a way to achieve this?
Thank you
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### Author:  [@Forrest](https://discourse.vtk.org/u/Forrest)
#### Post date: [March 7, 2022, 2:48pm UTC](https://discourse.vtk.org/t/reslicemapper-setlookuptable-is-not-a-function/8003/2 "2022-03-07T14:48:58Z")
You can use `imageSlice.getProperty().setPiecewiseFunction(pwf)` to translate voxel values into opacity levels. You can see an example here: [vtk.js](https://kitware.github.io/vtk-js/examples/ImageMapper.html)
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### Author:  [@dexter](https://discourse.vtk.org/u/dexter)
#### Post date: [March 7, 2022, 3:45pm UTC](https://discourse.vtk.org/t/reslicemapper-setlookuptable-is-not-a-function/8003/3 "2022-03-07T15:45:03Z")
> [@Forrest](#):
>
> setPiecewiseFunction
Thank you for your answer, I did what you told me, it is working fine!
```auto
const ofun = vtkPiecewiseFunction.newInstance();
ofun.addPoint(0, 1);
ofun.addPoint(150, 1);
ofun.addPoint(180, 0);
ofun.addPoint(255, 0);
obj.resliceActor1.getProperty().setPiecewiseFunction(ofun)
```
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### Author:  [@Forrest](https://discourse.vtk.org/u/Forrest)
#### Post date: [March 7, 2022, 5:37pm UTC](https://discourse.vtk.org/t/reslicemapper-setlookuptable-is-not-a-function/8003/4 "2022-03-07T17:37:44Z")
**Edit update** : the email contents don’t match up with the actual post contents, so ignore this post. I’ll leave it for posterity, but it answers a question that is no longer being asked.
* * *
> What you’ve just defined is the following:
>
> - voxels with values 0-150 have opacity 1
> - voxels with values 150-180 have linearly decreasing opacity from 1 to 0
> - voxels with values 80-255 have opacity 0
>
> If you want black (typically taken to be value 0), to be transparent, then set it to opacity 0.