# Transparent NaN scalars (vtk.js)
**URL:** https://discourse.vtk.org/t/transparent-nan-scalars-vtk-js/5167
**Category:** Web
**Created:** [February 10, 2021, 8:52am UTC](https://discourse.vtk.org/t/transparent-nan-scalars-vtk-js/5167 "2021-02-10T08:52:02Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@Uros\_Stankovic](https://discourse.vtk.org/u/Uros_Stankovic)
#### Post date: [February 10, 2021, 8:52am UTC](https://discourse.vtk.org/t/transparent-nan-scalars-vtk-js/5167/1 "2021-02-10T08:52:02Z")
On the picture gray areas have NaN value, i need them to be transparent.
I used lookupTable.setNanColor(1.0, 1.0, 1.0, 0), but alpha value doesn’t work.
```
const lookupTable = vtkColorTransferFunction.newInstance();
const preset = vtkColorMaps.getPresetByName('Cool to Warm');
lookupTable.applyColorMap(preset);
lookupTable.updateRange();
// lookupTable.addRGBPoint(0, 1.0, 0.0, 0.0);
// lookupTable.addRGBPoint(1, 0.0, 0.0, 1.0);
lookupTable.setNanColor(1.0, 1.0, 1.0, 0);
lookupTable.build();
mapper.setLookupTable(lookupTable);
```
---
### Author:  [@ken-martin](https://discourse.vtk.org/u/ken-martin)
#### Post date: [February 11, 2021, 3:31pm UTC](https://discourse.vtk.org/t/transparent-nan-scalars-vtk-js/5167/2 "2021-02-11T15:31:33Z")
Colortransferfunction does not handle opacity, only color. Give LookupTable a try as it handles opacity as well as color.
---
### Author:  [@Uros\_Stankovic](https://discourse.vtk.org/u/Uros_Stankovic)
#### Post date: [February 12, 2021, 8:34am UTC](https://discourse.vtk.org/t/transparent-nan-scalars-vtk-js/5167/3 "2021-02-12T08:34:53Z")
If i use only mapper.getLookupTable().setNanColor(1.0, 1.0, 1.0, 0); then it works, but if i use like this it won’t work
```
const lookupTable = vtkColorTransferFunction.newInstance();
const preset = vtkColorMaps.getPresetByName('Cool to Warm');
lookupTable.applyColorMap(preset);
mapper.setLookupTable(lookupTable);
mapper.getLookupTable().setNanColor(1.0, 1.0, 1.0, 0);
```
I need to have option to change color pallete and to set opacity. How to do that with default lookupTable, obviously i cant use vtkColorTransferFunction .
---
### Author:  [@Sebastien\_Jourdain](https://discourse.vtk.org/u/Sebastien_Jourdain)
#### Post date: [February 12, 2021, 3:27pm UTC](https://discourse.vtk.org/t/transparent-nan-scalars-vtk-js/5167/4 "2021-02-12T15:27:02Z")
The default LookupTable is that [one](https://github.com/Kitware/vtk-js/tree/master/Sources/Common/Core/LookupTable).
---
### Author:  [@Uros\_Stankovic](https://discourse.vtk.org/u/Uros_Stankovic)
#### Post date: [February 17, 2021, 1:39pm UTC](https://discourse.vtk.org/t/transparent-nan-scalars-vtk-js/5167/5 "2021-02-17T13:39:23Z")
This is my working code.
```
let rgbColor = [
[16, 52, 166, 255],
[65, 47, 136, 255],
[114, 43, 106, 255],
[162, 38, 75, 255],
[211, 33, 45, 255],
[246, 45, 45, 255]
]
const table = vtkDataArray.newInstance({
numberOfComponents: 4,
size: 4 * rgbColor.length,
dataType: 'Uint8Array',
});
for (let i = 0; i < rgbColor.length; i++) {
table.setTuple(i, rgbColor[i]);
}
mapper.getLookupTable().setNanColor(1.0, 1.0, 1.0, 0);
mapper.getLookupTable().setTable(table);
```
This is the only way, opacity and color work together.
