CardinalSpline
VTKExamples/Cxx/Utilities/CardinalSpline
Description¶
This example takes two points that have associated scalar values and allows you to interpolate the value at any point on the line between them using cardinal spline interpolation.
Code¶
CardinalSpline.cxx
#include <vtkSmartPointer.h> #include <vtkCardinalSpline.h> #include <vtkFloatArray.h> int main(int, char *[]) { // Create a scalar array. The array could be associated with the scalars of a vtkDataSet vtkSmartPointer<vtkFloatArray> distances = vtkSmartPointer<vtkFloatArray>::New(); distances->SetNumberOfComponents(1); distances->SetName("Distances"); distances->InsertNextValue(100.0); distances->InsertNextValue(300.0); // Create a cardinal spline to show how to linearly interpolate between two scalar values vtkSmartPointer<vtkCardinalSpline> spline = vtkSmartPointer<vtkCardinalSpline>::New(); spline->ClosedOff(); // Set the left and right second derivatives to 0 corresponding to linear interpolation spline->SetLeftConstraint(2); spline->SetLeftValue(0); spline->SetRightConstraint(2); spline->SetRightValue(0); double* r = distances->GetRange(); double xmin = r[0]; double xmax = r[1]; double length = xmax-xmin; for( vtkIdType i = 0; i < distances->GetNumberOfTuples(); ++i ) { double x = distances->GetTuple1(i); double t = (x - xmin)/length; spline->AddPoint( t, x ); } // Evaluate every 50 distance units along the line std::cout << "Spline interpolation:" << std::endl; double dt = .25; for( double t = dt ; t <= 1. - dt; t += dt ) { std::cout << "t: " << t << " value = " << spline->Evaluate(t) << std::endl; } return EXIT_SUCCESS; }
CMakeLists.txt¶
cmake_minimum_required(VERSION 2.8) PROJECT(CardinalSpline) find_package(VTK REQUIRED) include(${VTK_USE_FILE}) add_executable(CardinalSpline MACOSX_BUNDLE CardinalSpline.cxx) target_link_libraries(CardinalSpline ${VTK_LIBRARIES})
Download and Build CardinalSpline¶
Danger
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Click here to download CardinalSpline and its CMakeLists.txt file. Once the tarball CardinalSpline.tar has been downloaded and extracted,
cd CardinalSpline/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:
./CardinalSpline
WINDOWS USERS PLEASE NOTE: Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.