PerspectiveTransform
VTKExamples/Cxx/SimpleOperations/PerspectiveTransform
Description¶
The perspective transform automatically appends the "homogeneous 1" to the point before it is multiplied by the matrix. It then divides the first 3 coordinates of the result by the 4th coordinate of the result. For comparison, the standard projection (vtkTransform) is also performed with the same matrix and the same point. Note that the results are much different.
Code¶
PerspectiveTransform.cxx
#include <vtkSmartPointer.h> #include <vtkPerspectiveTransform.h> #include <vtkTransform.h> #include <vtkMatrix4x4.h> int main(int, char *[]) { vtkSmartPointer<vtkMatrix4x4> m = vtkSmartPointer<vtkMatrix4x4>::New(); m->SetElement(0,0,1); m->SetElement(0,1,2); m->SetElement(0,2,3); m->SetElement(0,3,4); m->SetElement(1,0,2); m->SetElement(1,1,2); m->SetElement(1,2,3); m->SetElement(1,3,4); m->SetElement(2,0,3); m->SetElement(2,1,2); m->SetElement(2,2,3); m->SetElement(2,3,4); m->SetElement(3,0,4); m->SetElement(3,1,2); m->SetElement(3,2,3); m->SetElement(3,3,4); vtkSmartPointer<vtkPerspectiveTransform> perspectiveTransform = vtkSmartPointer<vtkPerspectiveTransform>::New(); perspectiveTransform->SetMatrix(m); vtkSmartPointer<vtkTransform> transform = vtkSmartPointer<vtkTransform>::New(); transform->SetMatrix(m); double p[3]; p[0] = 1.0; p[1] = 2.0; p[2] = 3.0; double normalProjection[3]; transform->TransformPoint(p, normalProjection); std::cout << "Standard projection: " << normalProjection[0] << " " << normalProjection[1] << " " << normalProjection[2] << std::endl; double perspectiveProjection[3]; perspectiveTransform->TransformPoint(p, perspectiveProjection); std::cout << "Perspective projection: " << perspectiveProjection[0] << " " << perspectiveProjection[1] << " " << perspectiveProjection[2] << std::endl; return EXIT_SUCCESS; }
CMakeLists.txt¶
cmake_minimum_required(VERSION 2.8) PROJECT(PerspectiveTransform) find_package(VTK REQUIRED) include(${VTK_USE_FILE}) add_executable(PerspectiveTransform MACOSX_BUNDLE PerspectiveTransform.cxx) target_link_libraries(PerspectiveTransform ${VTK_LIBRARIES})
Download and Build PerspectiveTransform¶
Danger
The generation of tar files has not been ported to the new VTKExamples. Some tarballs may be missing or out-of-date.
Click here to download PerspectiveTransform and its CMakeLists.txt file. Once the tarball PerspectiveTransform.tar has been downloaded and extracted,
cd PerspectiveTransform/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:
./PerspectiveTransform
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.