# InterpolateCamera

vtk-examples/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.

Question

### Code¶

InterpolateCamera.cxx

#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkCameraInterpolator.h>
#include <vtkMinimalStandardRandomSequence.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPoints.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSmartPointer.h>

#include <vtkSphereSource.h>

#include <vtksys/SystemTools.hxx>

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

namespace {

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

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

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

vtkNew<vtkNamedColors> colors;

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

// Setup camera views for interpolation
vtkNew<vtkCameraInterpolator> interpolator;
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;
vtkNew<vtkCamera> cam;
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);
}

// Visualize
vtkNew<vtkPolyDataMapper> mapper;
mapper->SetInputData(polyData);
mapper->ScalarVisibilityOff();

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

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

vtkNew<vtkRenderer> renderer;
vtkNew<vtkRenderWindow> renderWindow;
renderWindow->SetSize(640, 480);
renderWindow->SetWindowName("InterpolateCamera");

vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
renderWindowInteractor->SetRenderWindow(renderWindow);

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

vtkNew<vtkCamera> camera;
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();
}

renderWindowInteractor->Start();

return EXIT_SUCCESS;
}

namespace {
{
vtkSmartPointer<vtkPolyData> polyData;
std::string extension =
vtksys::SystemTools::GetFilenameLastExtension(std::string(fileName));
if (extension == ".ply")
{
}
else if (extension == ".vtp")
{
}
else if (extension == ".obj")
{
}
else if (extension == ".stl")
{
}
else if (extension == ".vtk")
{
}
else if (extension == ".g")
{
}
else
{
vtkNew<vtkSphereSource> source;
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);

vtkNew<vtkMinimalStandardRandomSequence> randomSequence;
randomSequence->SetSeed(4355412);

// 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);
double factor = randomSequence->GetRangeValue(1.0, 3.0);
randomSequence->Next();
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 3.12 FATAL_ERROR)

project(InterpolateCamera)

find_package(VTK COMPONENTS
CommonColor
CommonCore
IOGeometry
IOLegacy
IOPLY
IOXML
InteractionStyle
RenderingContextOpenGL2
RenderingCore
RenderingFreeType
RenderingGL2PSOpenGL2
RenderingOpenGL2
)

if (NOT VTK_FOUND)
message(FATAL_ERROR "InterpolateCamera: 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.")
target_link_libraries(InterpolateCamera PRIVATE ${VTK_LIBRARIES} ) # vtk_module_autoinit is needed vtk_module_autoinit( TARGETS InterpolateCamera MODULES${VTK_LIBRARIES}
)


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


WINDOWS USERS

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