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.

Other Languages

See (Java), (CSharp)

Question

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 3.3 FATAL_ERROR)

project(PerspectiveTransform)

find_package(VTK COMPONENTS
vtkCommonCore
vtkCommonMath
vtkCommonTransforms QUIET)
if (NOT VTK_FOUND)
message("Skipping PerspectiveTransform: ${VTK_NOT_FOUND_MESSAGE}") return () endif() message (STATUS "VTK_VERSION:${VTK_VERSION}")
if (VTK_VERSION VERSION_LESS "8.90.0")
# old system
include(${VTK_USE_FILE}) add_executable(PerspectiveTransform MACOSX_BUNDLE PerspectiveTransform.cxx ) target_link_libraries(PerspectiveTransform PRIVATE${VTK_LIBRARIES})
else ()
# include all components
target_link_libraries(PerspectiveTransform PRIVATE ${VTK_LIBRARIES}) # vtk_module_autoinit is needed vtk_module_autoinit( TARGETS PerspectiveTransform MODULES${VTK_LIBRARIES}
)
endif ()


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

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