vtk范围映射 -1 ~ +1 映射到 0 ~ 255

来源: https://www.ilikebigbits.com/2015_02_05_remap.html

inline float remap(float x, float in_min, float in_max,
                   float out_min, float out_max)
{
    float t = (x - in_min) / (in_max - in_min);
    return lerp(out_min, out_max, t);
}

inline float remap_clamp(float x, float in_min, float in_max,
                         float out_min, float out_max)
{
    float t = (x - in_min) / (in_max - in_min);
    t = clamp(t, 0, 1);
    return lerp(out_min, out_max, t);
}

//示例：
normal_encoded = remap(normal, -1, +1, 0, 255);
alpha = remap_clamp(time, fade_start, fade_stop, 1, 0);

//vtk 也有类似的方法 ，将距离标量 转为颜色的图表的。
vtkNew<vtkDistancePolyDataFilter> distanceFilter;

  distanceFilter->SetInputConnection(0, clean1->GetOutputPort());
  distanceFilter->SetInputConnection(1, clean2->GetOutputPort());
  distanceFilter->Update();

  vtkNew<vtkPolyDataMapper> mapper;
  mapper->SetInputConnection(distanceFilter->GetOutputPort());
  mapper->SetScalarRange(
      distanceFilter->GetOutput()->GetPointData()->GetScalars()->GetRange()[0],
      distanceFilter->GetOutput()->GetPointData()->GetScalars()->GetRange()[1]);


  vtkNew<vtkScalarBarActor> scalarBar;
  scalarBar->SetLookupTable(mapper->GetLookupTable());
  scalarBar->SetTitle("Distance");
  scalarBar->SetNumberOfLabels(4);
  scalarBar->UnconstrainedFontSizeOn();