FitToHeightMap

VTKExamples/Cxx/Meshes/FitToHeightMap

Description¶

This example uses vtkFitToHeightMapFilter to cover a height map with vtkPolyData generated by a vtkPlaneSource. The plane's origin, point1 and point2 are calculated from the DEM's bounding box. The z coordinate of each parameter is set to the height of the DEM. With this plane, the example uses vtkProbeFilter to apply the scalar elevation data from the DEM. vtkWarpScalar is used to "elevate" the DEM mesh. Once he planes are draped over the warped DEM mesh, they are displayed side-by-side using the same vtkLookupTable.

The displayed meshes are original (left), point fit (middle) and cell fit (right).

Note

DEM files for the United States are available here.

Info

This example requires vtk version 8.2 or newer.

Code¶

FitToHeightMap.cxx

#include <vtkSmartPointer.h>
#include <vtkFitToHeightMapFilter.h>
#include <vtkDEMReader.h>
#include <vtkProbeFilter.h>

#include <vtkActor.h>
#include <vtkProperty.h>
#include <vtkCamera.h>
#include <vtkCellArray.h>
#include <vtkImageData.h>
#include <vtkImageDataGeometryFilter.h>
#include <vtkLookupTable.h>
#include <vtkPlaneSource.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkTriangleFilter.h>
#include <vtkWarpScalar.h>

#include <vtkNamedColors.h>

int main (int argc, char * argv[])
{
  if (argc < 2)
  {
    std::cout << "Uagse: " << argv[0] << " file.dem" << std::endl;
    return EXIT_FAILURE;
  }
// Create the RenderWindow, Renderer
//
  vtkSmartPointer<vtkNamedColors> colors =
    vtkSmartPointer<vtkNamedColors>::New();

  vtkSmartPointer<vtkRenderer> ren0 =
    vtkSmartPointer<vtkRenderer>::New();
  ren0->SetViewport(0, 0, 1.0/3.0 ,1);
  ren0->SetBackground(colors->GetColor3d("Wheat").GetData());

  vtkSmartPointer<vtkRenderer> ren1 =
    vtkSmartPointer<vtkRenderer>::New();
  ren1->SetViewport(1.0/3.0, 0, 2.0/3.0, 1);
  ren1->SetBackground(colors->GetColor3d("BurlyWood").GetData());

  vtkSmartPointer<vtkRenderer> ren2 =
    vtkSmartPointer<vtkRenderer>::New();
  ren2->SetViewport(2.0/3.0, 0, 1, 1);
  ren2->SetBackground(colors->GetColor3d("Tan").GetData());

  vtkSmartPointer<vtkRenderWindow> renderWindow =
    vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->SetSize (1200, 400);
  renderWindow->AddRenderer(ren0);
  renderWindow->AddRenderer(ren1);
  renderWindow->AddRenderer(ren2);

  vtkSmartPointer<vtkRenderWindowInteractor> interactor =
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  interactor->SetRenderWindow(renderWindow);

// Create pipeline. Load terrain data.
//
  vtkSmartPointer<vtkLookupTable> lut =
    vtkSmartPointer<vtkLookupTable>::New();
  lut->SetHueRange(0.6, 0);
  lut->SetSaturationRange(1.0, 0);
  lut->SetValueRange(0.5, 1.0);

// Read the data: a height field results
  vtkSmartPointer<vtkDEMReader> demReader =
    vtkSmartPointer<vtkDEMReader>::New();
  demReader->SetFileName(argv[1]);
  demReader->Update(); // Update so we can get bounds

  vtkSmartPointer<vtkImageDataGeometryFilter> surface =
    vtkSmartPointer<vtkImageDataGeometryFilter>::New();
  surface->SetInputConnection(demReader->GetOutputPort());

  // Warp the surface in the vertical direction
  vtkSmartPointer<vtkWarpScalar> warp =
    vtkSmartPointer<vtkWarpScalar>::New();
  warp->SetInputConnection(surface->GetOutputPort());
  warp->SetScaleFactor(1);
  warp->UseNormalOn();
  warp->SetNormal(0, 0, 1);
  warp->Update();

// Show the terrain
  double lo = demReader->GetOutput()->GetScalarRange()[0];
  double hi = demReader->GetOutput()->GetScalarRange()[1];

  vtkSmartPointer<vtkPolyDataMapper> demMapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  demMapper->SetInputConnection(warp->GetOutputPort());
  demMapper->ScalarVisibilityOn();
  demMapper->SetScalarRange(lo, hi);
  demMapper->SetLookupTable(lut);

  vtkSmartPointer<vtkActor> demActor =
    vtkSmartPointer<vtkActor>::New();
  demActor->SetMapper(demMapper);

  // Create polygon(s) to fit. z-values should be height of DEM
  // to accomodate ProbeFilter
  double zLevel = demReader->GetOutput()->GetBounds()[5];
  double *demBounds;
  demBounds = demReader->GetOutput()->GetBounds();

  vtkSmartPointer<vtkPlaneSource> plane =
    vtkSmartPointer<vtkPlaneSource>::New();
  plane->SetOrigin(demBounds[0], demBounds[2], zLevel);
  plane->SetPoint1(demBounds[1], demBounds[2], zLevel);
  plane->SetPoint2(demBounds[0], demBounds[3], zLevel);
  plane->SetResolution(128, 128);
  plane->Update();

  // Get the scalrs from the DEM
  vtkSmartPointer<vtkProbeFilter> probeDem =
    vtkSmartPointer<vtkProbeFilter>::New();
  probeDem->SetSourceData(demReader->GetOutput());
  probeDem->SetInputConnection(plane->GetOutputPort());
  probeDem->Update();

  // Fit polygons to surface using two strategies
  // Both will share the same lookup tables
  vtkSmartPointer<vtkFitToHeightMapFilter> pointFit =
    vtkSmartPointer<vtkFitToHeightMapFilter>::New();
  pointFit->SetInputConnection(probeDem->GetOutputPort());
  pointFit->SetHeightMapConnection(demReader->GetOutputPort());
  pointFit->SetFittingStrategyToPointProjection();
  pointFit->UseHeightMapOffsetOn();

  vtkSmartPointer<vtkPolyDataMapper> pointMapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  pointMapper->SetInputConnection(pointFit->GetOutputPort());
  pointMapper->ScalarVisibilityOn();
  pointMapper->SetScalarRange(lo, hi);
  pointMapper->SetLookupTable(lut);

  vtkSmartPointer<vtkActor> pointActor =
    vtkSmartPointer<vtkActor>::New();
  pointActor->SetMapper(pointMapper);

  // Fit polygons to surface (cell strategy)
  vtkSmartPointer<vtkFitToHeightMapFilter> cellFit =
    vtkSmartPointer<vtkFitToHeightMapFilter>::New();
  cellFit->SetInputConnection(probeDem->GetOutputPort());
  cellFit->SetHeightMapConnection(demReader->GetOutputPort());
  cellFit->SetFittingStrategyToCellAverageHeight();
  cellFit->UseHeightMapOffsetOn();

  vtkSmartPointer<vtkPolyDataMapper> cellMapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  cellMapper->SetInputConnection(cellFit->GetOutputPort());
  cellMapper->ScalarVisibilityOn();
  cellMapper->SetScalarRange(lo, hi);
  cellMapper->SetLookupTable(lut);

  vtkSmartPointer<vtkActor> cellActor =
    vtkSmartPointer<vtkActor>::New();
  cellActor->SetMapper(cellMapper);

  // Render the three representations
  ren0->AddActor(demActor);
  ren1->AddActor(pointActor);
  ren2->AddActor(cellActor);

  // Look down the x axis
  ren0->GetActiveCamera()->SetPosition( 1, 0, 0);
  ren0->GetActiveCamera()->SetFocalPoint( 0, 1, 0);
  ren0->GetActiveCamera()->SetViewUp( 0, 0, 1);
  ren0->ResetCamera();

  // Rotate to an oblique view
  ren0->GetActiveCamera()->Azimuth(30.0);
  ren0->GetActiveCamera()->Elevation(60.0);

  // Share the cameras
  ren1->SetActiveCamera(ren0->GetActiveCamera());
  ren2->SetActiveCamera(ren0->GetActiveCamera());

  renderWindow->Render();
  interactor->Start();
  return EXIT_SUCCESS;
}

CMakeLists.txt¶

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(FitToHeightMap)

find_package(VTK COMPONENTS 
  vtkCommonColor
  vtkCommonCore
  vtkCommonDataModel
  vtkFiltersCore
  vtkFiltersGeneral
  vtkFiltersGeometry
  vtkFiltersModeling
  vtkFiltersSources
  vtkIOImage
  vtkInteractionStyle
  vtkRenderingContextOpenGL2
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingGL2PSOpenGL2
  vtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
  message("Skipping FitToHeightMap: ${VTK_NOT_FOUND_MESSAGE}")
  return ()
endif()
message (STATUS "VTK_VERSION: ${VTK_VERSION}")
if (VTK_VERSION VERSION_LESS "8.90.0")
  # old system
  include(${VTK_USE_FILE})
  add_executable(FitToHeightMap MACOSX_BUNDLE FitToHeightMap.cxx )
  target_link_libraries(FitToHeightMap PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(FitToHeightMap MACOSX_BUNDLE FitToHeightMap.cxx )
  target_link_libraries(FitToHeightMap PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS FitToHeightMap
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build FitToHeightMap¶

Click here to download FitToHeightMap and its CMakeLists.txt file. Once the tarball FitToHeightMap.tar has been downloaded and extracted,

cd FitToHeightMap/build

If VTK is installed:

cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

Build the project:

make

and run it:

./FitToHeightMap

WINDOWS USERS

Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.