InterpolateCamera

VTKEx/Cxx/Rendering/InterpolateCamera

Description¶

This example uses vtkCameraInterpolator to generate a smooth interpolation between camera views. The key points for the cameras' positions are generated from the vtkPolyData's bounding box. The cameras' focal points are at the center of the polydata.

The key points are computed from the corners of the bounding box. They are pushed out along a vector from the center to the corner point. The amount of pushing is a random multiplier of the range of the data.

Code¶

InterpolateCamera.cxx

#include <vtkCameraInterpolator.h>
#include <vtkSmartPointer.h>

#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkNamedColors.h>
#include <vtkPoints.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>

#include <vtkBYUReader.h>
#include <vtkOBJReader.h>
#include <vtkPLYReader.h>
#include <vtkPolyDataReader.h>
#include <vtkSTLReader.h>
#include <vtkSphereSource.h>
#include <vtkXMLPolyDataReader.h>

#include <vtksys/SystemTools.hxx>

#include <array>
#include <chrono>
#include <iterator>
#include <thread>
#include <vector>
#include <random>

template <class T, std::size_t N>
ostream &operator<<(ostream &o, const std::array<T, N> &arr)
{
  copy(arr.cbegin(), arr.cend(), std::ostream_iterator<T>(o, ", "));
  return o;
}

template <class T, std::size_t N>
ostream &operator<<(ostream &o, const std::vector<T> &vec)
{
  copy(vec.cbegin(), vec.cend(), std::ostream_iterator<T>(o, ", "));
  return o;
}

namespace
{
vtkSmartPointer<vtkPolyData> ReadPolyData(const char *fileName);

void ComputeKeyPoints(vtkPolyData *polyData, std::array<double, 3> &center,
                      std::vector<std::array<double, 3>> &keyPoints);
}

int main(int argc, char *argv[]) {

  vtkSmartPointer<vtkNamedColors> colors =
      vtkSmartPointer<vtkNamedColors>::New();

  vtkSmartPointer<vtkPolyData> polyData = ReadPolyData(argc > 1 ? argv[1] : "");


  // Setup camera views for interpolation
  vtkSmartPointer<vtkCameraInterpolator> interpolator =
      vtkSmartPointer<vtkCameraInterpolator>::New();
  interpolator->SetInterpolationTypeToSpline();

  std::array<double, 3> center;
  std::vector<std::array<double, 3>> keyPoints;
  ComputeKeyPoints(polyData, center, keyPoints);

  for (size_t i = 0; i < keyPoints.size() + 1; ++i) {
    auto j = i;
    vtkSmartPointer<vtkCamera> cam =
        vtkSmartPointer<vtkCamera>::New();
    cam->SetFocalPoint(center.data());
    if (i < keyPoints.size())
    {
      cam->SetPosition(keyPoints[i].data());
    }
    else
    {
      cam->SetPosition(keyPoints[0].data());
    }
    cam->SetViewUp(0.0, 0.0, 1.0);
    interpolator->AddCamera((double)i, cam);
  }

  // Visualize
  vtkSmartPointer<vtkPolyDataMapper> mapper =
      vtkSmartPointer<vtkPolyDataMapper>::New();
  mapper->SetInputData(polyData);
  mapper->ScalarVisibilityOff();

  vtkSmartPointer<vtkProperty> backProp =
      vtkSmartPointer<vtkProperty>::New();
  backProp->SetDiffuseColor(colors->GetColor3d("Banana").GetData());
  backProp->SetDiffuse(.76);
  backProp->SetSpecular(.4);
  backProp->SetSpecularPower(30);
  ;

  vtkSmartPointer<vtkActor> actor =
      vtkSmartPointer<vtkActor>::New();
  actor->SetMapper(mapper);
  actor->SetBackfaceProperty(backProp);
  actor->GetProperty()->SetDiffuseColor(
      colors->GetColor3d("Crimson").GetData());
  actor->GetProperty()->SetSpecular(.6);
  actor->GetProperty()->SetSpecularPower(30);


  vtkSmartPointer<vtkRenderer> renderer =
      vtkSmartPointer<vtkRenderer>::New();
  vtkSmartPointer<vtkRenderWindow> renderWindow =
      vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->AddRenderer(renderer);
  renderWindow->SetSize(640, 480);

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

  renderer->AddActor(actor);
  renderer->SetBackground(colors->GetColor3d("Silver").GetData());

  vtkSmartPointer<vtkCamera> camera =
      vtkSmartPointer<vtkCamera>::New();
  renderer->SetActiveCamera(camera);

  auto numSteps = 600;
  auto minT = interpolator->GetMinimumT();
  auto maxT = interpolator->GetMaximumT();
  for (auto i = 0; i < numSteps; ++i)
  {
    double t = (double)i * (maxT - minT) / (double)(numSteps - 1);
    interpolator->InterpolateCamera(t, camera);
    renderer->ResetCameraClippingRange();
    renderWindow->Render();
    std::this_thread::sleep_for(std::chrono::milliseconds(50));
  }

  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

namespace
{
vtkSmartPointer<vtkPolyData> ReadPolyData(const char *fileName)
{
  vtkSmartPointer<vtkPolyData> polyData;
  std::string extension =
      vtksys::SystemTools::GetFilenameLastExtension(std::string(fileName));
  if (extension == ".ply")
  {
    vtkSmartPointer<vtkPLYReader> reader =
        vtkSmartPointer<vtkPLYReader>::New();
    reader->SetFileName(fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".vtp")
  {
    vtkSmartPointer<vtkXMLPolyDataReader> reader =
        vtkSmartPointer<vtkXMLPolyDataReader>::New();
    reader->SetFileName(fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".obj")
  {
    vtkSmartPointer<vtkOBJReader> reader =
        vtkSmartPointer<vtkOBJReader>::New();
    reader->SetFileName(fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".stl")
  {
    vtkSmartPointer<vtkSTLReader> reader =
        vtkSmartPointer<vtkSTLReader>::New();
    reader->SetFileName(fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".vtk")
  {
    vtkSmartPointer<vtkPolyDataReader> reader =
        vtkSmartPointer<vtkPolyDataReader>::New();
    reader->SetFileName(fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".g") {
    vtkSmartPointer<vtkBYUReader> reader =
        vtkSmartPointer<vtkBYUReader>::New();
    reader->SetGeometryFileName(fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else 
  {
    vtkSmartPointer<vtkSphereSource> source =
        vtkSmartPointer<vtkSphereSource>::New();
    source->Update();
    polyData = source->GetOutput();
  }
  return polyData;
}

void ComputeKeyPoints(vtkPolyData *polyData, std::array<double, 3> &center,
                      std::vector<std::array<double, 3>> &keyPoints)
{
  std::mt19937 mt(4355412); //Standard mersenne_twister_engine
  std::uniform_real_distribution<double> dis(1.0, 3.0);

  // Get Bounding Box
  std::array<double, 6> bounds;
  polyData->GetBounds(bounds.data());

  double range;
  range = std::max(std::max(bounds[1] - bounds[0], bounds[3] - bounds[2]),
                   bounds[5] - bounds[3]);

  std::vector<std::array<double, 3>> points(8);
  std::array<double, 3> point;
  point = {{bounds[0], bounds[2], bounds[4]}};
  points[0] = point;

  point = {{bounds[1], bounds[2], bounds[4]}};
  points[1] = point;

  point = {{bounds[1], bounds[2], bounds[5]}};
  points[2] = point;

  point = {{bounds[0], bounds[2], bounds[5]}};
  points[3] = point;

  point = {{bounds[0], bounds[3], bounds[4]}};
  points[4] = point;

  point = {{bounds[1], bounds[3], bounds[4]}};
  points[5] = point;

  point = {{bounds[1], bounds[3], bounds[5]}};
  points[6] = point;

  point = {{bounds[0], bounds[3], bounds[5]}};
  points[7] = point;

  polyData->GetCenter(center.data());

  for (size_t i = 0; i < points.size(); ++i)
  {
    std::array<double, 3> direction;
    for (auto j = 0; j < 3; ++j)
    {
      direction[j] = points[i][j] - center[j];
    }
    vtkMath::Normalize(direction.data());
    double factor = dis(mt);
    keyPoints.resize(8);
    for (auto j = 0; j < 3; ++j)
    {
      keyPoints[i][j] = points[i][j] + direction[j] * range * factor;
    }
  }
}
} // namespace

CMakeLists.txt¶

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(InterpolateCamera)

find_package(VTK COMPONENTS 
  vtkCommonColor
  vtkCommonCore
  vtkFiltersSources
  vtkIOGeometry
  vtkIOLegacy
  vtkIOPLY
  vtkIOXML
  vtkInteractionStyle
  vtkRenderingContextOpenGL2
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingGL2PSOpenGL2
  vtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
  message("Skipping InterpolateCamera: ${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(InterpolateCamera MACOSX_BUNDLE InterpolateCamera.cxx )
  target_link_libraries(InterpolateCamera PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(InterpolateCamera MACOSX_BUNDLE InterpolateCamera.cxx )
  target_link_libraries(InterpolateCamera PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS InterpolateCamera
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build InterpolateCamera¶

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

cd InterpolateCamera/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:

./InterpolateCamera