# DecimateHawaii

VTKExamples/Cxx/VisualizationAlgorithms/DecimateHawaii

### Description¶

This examples shows reduction on the order of 90 percent for a 10:1 compression ratio. the wireframe image are shown to accentuate the density of the polygonal meshes. The left-hand image is the original data; the right-hand image is the decimated mesh.

Other Languages

See (Python)

Question

### Code¶

DecimateHawaii.cxx

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

int main (int argc, char *argv[])
{
if (argc < 2)
{
std::cout << "Usage: " << argv[0] << " honolulu.vtk" << std::endl;
return EXIT_FAILURE;
}

// This example shows how to use decimation to reduce a polygonal mesh. We also
// use mesh smoothing and generate surface normals to give a pleasing result.
//

hawaii->SetFileName(argv[1]);

// We want to preserve topology (not let any cracks form). This may limit
// the total reduction possible, which we have specified at 90%.
//
vtkSmartPointer<vtkDecimatePro> deci =
vtkSmartPointer<vtkDecimatePro>::New();
deci->SetInputConnection(hawaii->GetOutputPort());
deci->SetTargetReduction(0.9);
deci->PreserveTopologyOn();

vtkSmartPointer<vtkPolyDataNormals> decimatedNormals =
vtkSmartPointer<vtkPolyDataNormals>::New();
decimatedNormals->SetInputConnection(deci->GetOutputPort());
decimatedNormals->FlipNormalsOn();
decimatedNormals->SetFeatureAngle(60);

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

vtkSmartPointer<vtkPolyDataMapper> decimatedMapper =
vtkSmartPointer<vtkPolyDataMapper>::New();
decimatedMapper->SetInputConnection(decimatedNormals->GetOutputPort());

vtkSmartPointer<vtkActor> decimatedActor =
vtkSmartPointer<vtkActor>::New();
decimatedActor->SetMapper(decimatedMapper);
decimatedActor->GetProperty()->SetColor(colors->GetColor3d("Aqua").GetData());
decimatedActor->GetProperty()->SetRepresentationToWireframe();

vtkSmartPointer<vtkPolyDataMapper> originalMapper =
vtkSmartPointer<vtkPolyDataMapper>::New();
originalMapper->SetInputConnection(decimatedNormals->GetOutputPort());

vtkSmartPointer<vtkActor> originalActor =
vtkSmartPointer<vtkActor>::New();
originalActor->SetMapper(originalMapper);
originalActor->GetProperty()->SetColor(colors->GetColor3d("Aqua").GetData());

// Create the RenderWindow, Renderer and both Actors
//
vtkSmartPointer<vtkRenderer> renderer1 =
vtkSmartPointer<vtkRenderer>::New();
renderer1->SetViewport( 0., 0., 0.5, 1. );

vtkSmartPointer<vtkRenderer> renderer2 =
vtkSmartPointer<vtkRenderer>::New();
renderer2->SetViewport( 0.5, 0., 1., 1. );

vtkSmartPointer<vtkRenderWindow> renderWindow =
vtkSmartPointer<vtkRenderWindow>::New();

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

// Add the actors to the renderer, set the background and size
//
renderer1->SetBackground(colors->GetColor3d("Wheat").GetData());
renderer2->SetBackground(colors->GetColor3d("Papaya_Whip").GetData());
renderWindow->SetSize(800, 400);

// render the image
//
vtkSmartPointer<vtkCamera> cam1 =
vtkSmartPointer<vtkCamera>::New();
cam1->SetFocalPoint(0, 0, 0);
cam1->SetPosition(0, 0, 1);
cam1->SetViewUp(0, 1, 0);
renderer1->SetActiveCamera(cam1);
renderer2->SetActiveCamera(cam1);
renderer1->ResetCamera();
cam1->Azimuth(30);
cam1->Elevation(30);
cam1->Dolly(1.3);
renderer1->ResetCameraClippingRange();
renderWindow->Render();
interactor->Start();

return EXIT_SUCCESS;
}


### CMakeLists.txt¶

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(DecimateHawaii)

find_package(VTK COMPONENTS
vtkCommonColor
vtkFiltersCore
vtkIOImage
vtkIOLegacy
vtkInteractionStyle
vtkRenderingCore
vtkRenderingFreeType
vtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
message("Skipping DecimateHawaii: ${VTK_NOT_FOUND_MESSAGE}") return () endif() message (STATUS "VTK_VERSION:${VTK_VERSION}")
if (VTK_VERSION VERSION_LESS "8.90.0")
# old system
include(${VTK_USE_FILE}) add_executable(DecimateHawaii MACOSX_BUNDLE DecimateHawaii.cxx ) target_link_libraries(DecimateHawaii PRIVATE${VTK_LIBRARIES})
else ()
# include all components
target_link_libraries(DecimateHawaii PRIVATE ${VTK_LIBRARIES}) # vtk_module_autoinit is needed vtk_module_autoinit( TARGETS DecimateHawaii MODULES${VTK_LIBRARIES}
)
endif ()


cd DecimateHawaii/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:

./DecimateHawaii


WINDOWS USERS

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