Difference and use cases for `vtkMRMLProceduralColorNode` and `vtkMRMLColorTableNode`

Development
1

Hi,

I’m wondering what is the difference between vtkMRMLProceduralColorNode and vtkMRMLColorTableNode?
For example I can see that vtkMRMLColorTableNode creates discrete color map while vtkMRMLProceduralColorNode creates continous.

Maybe they serve to different purposes?

2

All these mode types can store both discrete and continuous (depending on what you set inside - color transfer function or lookup table).

Procedural color node is a special kind of color node that does not need to be saved into a file because the color function or table entries are generated programmatically.

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3

Thank you, that make sense

I just can’t find a method that triggers discrete or contigous color.
This is my attemt that results in discrete color map:

  vtkNew<vtkMRMLColorTableNode> bwrColorTable;

  bwrColorTable->SetType(vtkMRMLColorTableNode::User);
  bwrColorTable->HideFromEditorsOff();  // make the color table selectable in the GUI outside Colors module
  bwrColorTable->SetSaveWithScene(true);
  bwrColorTable->SetNumberOfColors(5);
  bwrColorTable->GetLookupTable()->SetTableRange(0.,1.);

  bwrColorTable->SetColor(0, 0.0,     0.0,    0.5,    1.0);
  bwrColorTable->SetColor(1, 0.0,     0.375,  0.8314, 0.5);
  bwrColorTable->SetColor(2, 1.0,     1.0,    1.0,    0.0);
  bwrColorTable->SetColor(3, 0.8314,  0.375,  0.0,    0.5);
  bwrColorTable->SetColor(4, 0.5,     0.0,    0.0,    1.0);

  bwrColorTable->SetName("BWR");
  bwrColorTable->SetScene(this->GetMRMLScene());
  bwrColorTable->SetHideFromEditors(false);
  this->GetMRMLScene()->AddNode(bwrColorTable);
4

You can find examples in the script repository:

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