Transparent NaN scalars (vtk.js)

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#1

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);

image
image1116×633 95.6 KB

#2

Colortransferfunction does not handle opacity, only color. Give LookupTable a try as it handles opacity as well as color.

#3

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 .

#4

The default LookupTable is that one.

#5

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.

image
image1275×813 444 KB

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