NormalsDemo
vtk-examples/Cxx/Visualization/NormalsDemo
Description¶
This example demonstrates the generation of normals. The left image shows the orignal faceted model. The center image shows the model with generated normals, but no consideration for sharp features. The third image shows the model with a 30 degree feature angle and splitting on.
Theis example uses the src/Testing/Data/42400-IDGH.stl
dataset.
Info
See Figure 9-24 in Chapter 9 The VTK Textbook.
Other languages
See (Python)
Question
If you have a question about this example, please use the VTK Discourse Forum
Code¶
NormalsDemo.cxx
#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkCleanPolyData.h>
#include <vtkColor.h>
#include <vtkImplicitBoolean.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkProperty.h>
#include <vtkBYUReader.h>
#include <vtkOBJReader.h>
#include <vtkPLYReader.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkPolyDataNormals.h>
#include <vtkPolyDataReader.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSTLReader.h>
#include <vtkSmartPointer.h>
#include <vtkSphereSource.h>
#include <vtkXMLPolyDataReader.h>
#include <vtksys/SystemTools.hxx>
namespace {
vtkSmartPointer<vtkPolyData> ReadPolyData(const char* fileName);
}
int main(int argc, char* argv[])
{
vtkSmartPointer<vtkPolyData> polyData = ReadPolyData(argc > 1 ? argv[1] : "");
vtkNew<vtkNamedColors> colors;
// A renderer and render window
vtkNew<vtkRenderer> renderer;
renderer->SetBackground(colors->GetColor3d("White").GetData());
// Create background colors for each viewport
std::vector<vtkColor3d> backgroundColors;
backgroundColors.push_back(colors->GetColor3d("Cornsilk"));
backgroundColors.push_back(colors->GetColor3d("NavajoWhite"));
backgroundColors.push_back(colors->GetColor3d("Tan"));
// Create a renderer for each view port
std::vector<vtkSmartPointer<vtkRenderer>> ren;
ren.push_back(vtkSmartPointer<vtkRenderer>::New());
ren.push_back(vtkSmartPointer<vtkRenderer>::New());
ren.push_back(vtkSmartPointer<vtkRenderer>::New());
ren[0]->SetViewport(0, 0, 1.0 / 3.0, 1); // Input
ren[1]->SetViewport(1.0 / 3.0, 0, 2.0 / 3.0, 1); // Normals (no split)
ren[2]->SetViewport(2.0 / 3.0, 0, 1, 1); // Normals (split)
// Shared camera
vtkNew<vtkCamera> camera;
vtkNew<vtkPolyDataNormals> normals;
normals->SetInputData(polyData);
normals->SetFeatureAngle(30.0);
for (int i = 0; i < 3; ++i)
{
if (i == 0)
{
normals->ComputePointNormalsOff();
}
else if (i == 1)
{
normals->ComputePointNormalsOn();
normals->SplittingOff();
}
else
{
normals->ComputePointNormalsOn();
normals->SplittingOn();
}
normals->Update();
vtkNew<vtkPolyData> normalsPolyData;
normalsPolyData->DeepCopy(normals->GetOutput());
// mapper
vtkNew<vtkPolyDataMapper> mapper;
mapper->SetInputData(normalsPolyData);
mapper->ScalarVisibilityOff();
vtkNew<vtkActor> actor;
actor->SetMapper(mapper);
actor->GetProperty()->SetDiffuseColor(
colors->GetColor3d("Peacock").GetData());
actor->GetProperty()->SetDiffuse(.7);
actor->GetProperty()->SetSpecularPower(20);
actor->GetProperty()->SetSpecular(.5);
// add the actor
ren[i]->SetBackground(backgroundColors[i].GetData());
ren[i]->SetActiveCamera(camera);
ren[i]->AddActor(actor);
}
// render window
vtkNew<vtkRenderWindow> renwin;
renwin->AddRenderer(ren[0]);
renwin->AddRenderer(ren[1]);
renwin->AddRenderer(ren[2]);
renwin->SetWindowName("NormalsDemo");
// An interactor
vtkNew<vtkRenderWindowInteractor> interactor;
interactor->SetRenderWindow(renwin);
renwin->SetSize(900, 300);
ren[0]->GetActiveCamera()->SetFocalPoint(0, 0, 0);
ren[0]->GetActiveCamera()->SetPosition(1, 0, 0);
ren[0]->GetActiveCamera()->SetViewUp(0, 0, -1);
ren[0]->ResetCamera();
ren[0]->GetActiveCamera()->Azimuth(120);
ren[0]->GetActiveCamera()->Elevation(30);
ren[0]->GetActiveCamera()->Dolly(1.1);
ren[0]->ResetCameraClippingRange();
renwin->Render();
ren[0]->ResetCamera();
renwin->Render();
// Start
interactor->Initialize();
interactor->Start();
return EXIT_SUCCESS;
}
namespace {
vtkSmartPointer<vtkPolyData> ReadPolyData(const char* fileName)
{
vtkSmartPointer<vtkPolyData> polyData;
std::string extension =
vtksys::SystemTools::GetFilenameExtension(std::string(fileName));
if (extension == ".ply")
{
vtkNew<vtkPLYReader> reader;
reader->SetFileName(fileName);
reader->Update();
polyData = reader->GetOutput();
}
else if (extension == ".vtp")
{
vtkNew<vtkXMLPolyDataReader> reader;
reader->SetFileName(fileName);
reader->Update();
polyData = reader->GetOutput();
}
else if (extension == ".vtk")
{
vtkNew<vtkPolyDataReader> reader;
reader->SetFileName(fileName);
reader->Update();
polyData = reader->GetOutput();
}
else if (extension == ".obj")
{
vtkNew<vtkOBJReader> reader;
reader->SetFileName(fileName);
reader->Update();
polyData = reader->GetOutput();
}
else if (extension == ".stl")
{
vtkNew<vtkSTLReader> reader;
reader->SetFileName(fileName);
reader->Update();
polyData = reader->GetOutput();
}
else if (extension == ".g")
{
vtkNew<vtkBYUReader> reader;
reader->SetGeometryFileName(fileName);
reader->Update();
polyData = reader->GetOutput();
}
else
{
vtkNew<vtkSphereSource> sphere;
sphere->SetPhiResolution(11);
sphere->SetThetaResolution(11);
sphere->Update();
polyData = sphere->GetOutput();
}
vtkNew<vtkCleanPolyData> clean;
clean->SetInputData(polyData);
clean->Update();
return clean->GetOutput();
}
} // namespace
CMakeLists.txt¶
cmake_minimum_required(VERSION 3.3 FATAL_ERROR)
project(NormalsDemo)
find_package(VTK COMPONENTS
vtkCommonColor
vtkCommonCore
vtkCommonDataModel
vtkFiltersCore
vtkFiltersSources
vtkIOGeometry
vtkIOLegacy
vtkIOPLY
vtkIOXML
vtkInteractionStyle
vtkRenderingContextOpenGL2
vtkRenderingCore
vtkRenderingFreeType
vtkRenderingGL2PSOpenGL2
vtkRenderingOpenGL2
QUIET
)
if (NOT VTK_FOUND)
message("Skipping NormalsDemo: ${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(NormalsDemo MACOSX_BUNDLE NormalsDemo.cxx )
target_link_libraries(NormalsDemo PRIVATE ${VTK_LIBRARIES})
else ()
# include all components
add_executable(NormalsDemo MACOSX_BUNDLE NormalsDemo.cxx )
target_link_libraries(NormalsDemo PRIVATE ${VTK_LIBRARIES})
# vtk_module_autoinit is needed
vtk_module_autoinit(
TARGETS NormalsDemo
MODULES ${VTK_LIBRARIES}
)
endif ()
Download and Build NormalsDemo¶
Click here to download NormalsDemo and its CMakeLists.txt file. Once the tarball NormalsDemo.tar has been downloaded and extracted,
cd NormalsDemo/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:
./NormalsDemo
WINDOWS USERS
Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.