# lookUpTable-\>SetRange() does not work?

**URL:** https://discourse.vtk.org/t/lookuptable-setrange-does-not-work/11703
**Category:** Support
**Created:** [June 13, 2023, 4:12pm UTC](https://discourse.vtk.org/t/lookuptable-setrange-does-not-work/11703 "2023-06-13T16:12:09Z")
**Posts on this page:** 2
**Page:** 1

<div class="post-metadata">

### Author: ![lake\_lagunita](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/l/48db29/32.png) [@lake\_lagunita](https://discourse.vtk.org/u/lake_lagunita)
#### Post date: [June 13, 2023, 4:12pm UTC](https://discourse.vtk.org/t/lookuptable-setrange-does-not-work/11703/1 "2023-06-13T16:12:10Z")

</div>

I am a beginner and I am trying to visualize a .vtu file (test.vtu) and show the points’ Z direction displacement.  
The follwing is my cxx and CMake code:

ReadUnstructuredGrid.cxx:

```auto
#include <vtkActor.h>
#include <vtkDataSetMapper.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSmartPointer.h>
#include <vtkXMLUnstructuredGridReader.h>
#include <vtkDataset.h>
#include <vtkCellData.h>
#include <vtkLookupTable.h>
#include <vtkUnstructuredGrid.h>
#include <vtkPointData.h>
#include <vtkDataArray.h>
#include <vtkScalarBarActor.h>
#include <vtkCameraOrientationWidget.h>

int main(int argc, char *argv[])
{
  // parse command line arguments
  if (argc < 2)
  {
    std::cerr << "Usage: " << argv[0] << " Filename(.vtu) e.g. tetra.vtu"
              << std::endl;
    return EXIT_FAILURE;
  }

  std::string filename = argv[1];

  // read all the data from the file
  vtkNew<vtkXMLUnstructuredGridReader> reader;
  reader->SetFileName(filename.c_str());
  reader->Update();

  vtkNew<vtkNamedColors> colors;

  vtkSmartPointer<vtkLookupTable> lut = vtkSmartPointer<vtkLookupTable>::New();
  lut->SetRange(0.0, 0.03); //the displacement ranges from 0 to 0.03
  lut->SetNumberOfColors(256);
  lut->Build();

  // Create a mapper and actor
  vtkNew<vtkDataSetMapper> mapper;
  vtkDataSet *dataSet = reader->GetOutputAsDataSet();
  dataSet->Print(std::cout);
  mapper->SetInputConnection(reader->GetOutputPort());
  mapper->ScalarVisibilityOn();

  mapper->SetLookupTable(lut);
  mapper->SetColorModeToMapScalars();
  mapper->SetScalarModeToUsePointFieldData();
  mapper->ColorByArrayComponent("Displacement", 2);

  vtkNew<vtkActor> actor;
  actor->SetMapper(mapper);
  actor->GetProperty()->SetOpacity(0.5);
  actor->GetProperty()->EdgeVisibilityOn();
  actor->GetProperty()->SetLineWidth(2.0);
  // actor->GetProperty()->SetColor(colors->GetColor3d("MistyRose").GetData());

  // vtkNew<vtkProperty> backFace;
  // backFace->SetColor(colors->GetColor3d("Tomato").GetData());
  // actor->SetBackfaceProperty(backFace);

  // add a scalarBar
  vtkNew<vtkScalarBarActor> colBar;
  colBar->SetMaximumHeightInPixels(500);
  colBar->SetLookupTable(lut);

  // Create a renderer, render window, and interactor
  vtkNew<vtkRenderer> renderer;
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->AddRenderer(renderer);
  vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
  renderWindowInteractor->SetRenderWindow(renderWindow);

  // Add the actor to the scene
  renderer->AddActor(actor);
  renderer->SetBackground(colors->GetColor3d("Wheat").GetData());
  renderer->AddActor2D(colBar);

  
  //add a xyz
  vtkNew<vtkCameraOrientationWidget> widgetCam;
  widgetCam->SetParentRenderer(renderer);
  widgetCam->On();

  // Render and interact
  renderWindow->SetSize(640, 480);

  renderWindow->Render();
  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

```

CMakeLists.txt:

```auto
cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(ReadUnstructuredGrid)

find_package(VTK COMPONENTS 
  CommonColor
  CommonCore
  IOXML
  InteractionStyle
  RenderingContextOpenGL2
  RenderingCore
  RenderingFreeType
  RenderingGL2PSOpenGL2
  RenderingOpenGL2
  RenderingAnnotation
  InteractionWidgets
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "ReadUnstructuredGrid: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
add_executable(ReadUnstructuredGrid MACOSX_BUNDLE ReadUnstructuredGrid.cxx )
  target_link_libraries(ReadUnstructuredGrid PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS ReadUnstructuredGrid
  MODULES ${VTK_LIBRARIES}
)

```

The test.vtu file has been validated by paraview that its displacement is from 0 to 0.03, thus I set the lookupTable range from 0 to 0.03, However, the colorBar still shows the range from 0 to 1 as the screenshot shows:

 ![image](https://discourse.vtk.org/uploads/default/original/2X/c/cb676fe0a1d39bb6a5cf6ad5888881f89499cffc.jpeg)

I am not sure if my code is correct, I just googled the relative information and followed those examples. So if there’re any mistake in my code, please correct it. Thank you  
[test.7z](https://discourse.vtk.org/uploads/short-url/40Zen6z42zYQXNSLnGNDeToZfGw.7z) (2.7 MB)

---

<div class="post-metadata">

### Author: ![Sebastien\_Jourdain](https://discourse.vtk.org/user_avatar/discourse.vtk.org/sebastien_jourdain/32/100_2.png) [@Sebastien\_Jourdain](https://discourse.vtk.org/u/Sebastien_Jourdain)
#### Post date: [June 13, 2023, 4:24pm UTC](https://discourse.vtk.org/t/lookuptable-setrange-does-not-work/11703/2 "2023-06-13T16:24:16Z")

</div>

Make sure you call [UseLookupTableScalarRangeOn()](https://vtk.org/doc/nightly/html/classvtkMapper.html#a1fe12cd422a63862237fbc49d64c7985) on your mapper.