GradientFilter
VTKExamples/Cxx/PolyData/GradientFilter
Description
Computes the gradient of a scalar field defined on the points of a data set.
Code
GradientFilter.cxx
#include <vtkSmartPointer.h>
#include <vtkActor.h>
#include <vtkArrowSource.h>
#include <vtkAssignAttribute.h>
#include <vtkCamera.h>
#include <vtkExtractEdges.h>
#include <vtkGlyph3D.h>
#include <vtkGradientFilter.h>
#include <vtkPolyDataMapper.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkTubeFilter.h>
#include <vtkUnstructuredGridReader.h>
int main(int argc, char *argv[])
{
if (argc < 2)
{
std::cerr << "Usage: " << argv[0]
<< " Filename(.vtk)" << std::endl;
}
// Create the reader for the data.
// This is the data that will be volume rendered.
std::string filename = argv[1];
std::cout << "Loading " << filename.c_str() << std::endl;
vtkSmartPointer<vtkUnstructuredGridReader> reader =
vtkSmartPointer<vtkUnstructuredGridReader>::New();
reader->SetFileName(filename.c_str());
vtkSmartPointer<vtkExtractEdges> edges =
vtkSmartPointer<vtkExtractEdges>::New();
edges->SetInputConnection(reader->GetOutputPort());
vtkSmartPointer<vtkTubeFilter> tubes =
vtkSmartPointer<vtkTubeFilter>::New();
tubes->SetInputConnection(edges->GetOutputPort());
tubes->SetRadius(0.0625);
tubes->SetVaryRadiusToVaryRadiusOff();
tubes->SetNumberOfSides(32);
vtkSmartPointer<vtkPolyDataMapper> tubesMapper =
vtkSmartPointer<vtkPolyDataMapper>::New();
tubesMapper->SetInputConnection(tubes->GetOutputPort());
tubesMapper->SetScalarRange(0.0, 26.0);
vtkSmartPointer<vtkActor> tubesActor =
vtkSmartPointer<vtkActor>::New();
tubesActor->SetMapper(tubesMapper);
vtkSmartPointer<vtkGradientFilter> gradients =
vtkSmartPointer<vtkGradientFilter>::New();
gradients->SetInputConnection(reader->GetOutputPort());
vtkSmartPointer<vtkAssignAttribute> vectors =
vtkSmartPointer<vtkAssignAttribute>::New();
vectors->SetInputConnection(gradients->GetOutputPort());
vectors->Assign("Gradients", vtkDataSetAttributes::VECTORS,
vtkAssignAttribute::POINT_DATA);
vtkSmartPointer<vtkArrowSource> arrow =
vtkSmartPointer<vtkArrowSource>::New();
vtkSmartPointer<vtkGlyph3D> glyphs =
vtkSmartPointer<vtkGlyph3D>::New();
glyphs->SetInputConnection(0, vectors->GetOutputPort());
glyphs->SetInputConnection(1, arrow->GetOutputPort());
glyphs->ScalingOn();
glyphs->SetScaleModeToScaleByVector();
glyphs->SetScaleFactor(0.25);
glyphs->OrientOn();
glyphs->ClampingOff();
glyphs->SetVectorModeToUseVector();
glyphs->SetIndexModeToOff();
vtkSmartPointer<vtkPolyDataMapper> glyphMapper =
vtkSmartPointer<vtkPolyDataMapper>::New();
glyphMapper->SetInputConnection(glyphs->GetOutputPort());
glyphMapper->ScalarVisibilityOff();
vtkSmartPointer<vtkActor> glyphActor =
vtkSmartPointer<vtkActor>::New();
glyphActor->SetMapper(glyphMapper);
vtkSmartPointer<vtkRenderer> renderer =
vtkSmartPointer<vtkRenderer>::New();
renderer->AddActor(tubesActor);
renderer->AddActor(glyphActor);
renderer->SetBackground(0.328125, 0.347656, 0.425781);
vtkSmartPointer<vtkRenderWindow> renwin =
vtkSmartPointer<vtkRenderWindow>::New();
renwin->AddRenderer(renderer);
renwin->SetSize(350, 500);
renderer->ResetCamera();
vtkCamera *camera = renderer->GetActiveCamera();
camera->Elevation(-80.0);
camera->OrthogonalizeViewUp();
camera->Azimuth(135.0);
vtkSmartPointer<vtkRenderWindowInteractor> iren =
vtkSmartPointer<vtkRenderWindowInteractor>::New();
iren->SetRenderWindow(renwin);
iren->Initialize();
iren->Start();
return EXIT_SUCCESS;
}
CMakeLists.txt
cmake_minimum_required(VERSION 2.8)
PROJECT(GradientFilter)
find_package(VTK REQUIRED)
include(${VTK_USE_FILE})
add_executable(GradientFilter MACOSX_BUNDLE GradientFilter.cxx)
target_link_libraries(GradientFilter ${VTK_LIBRARIES})
Download and Build GradientFilter
Click here to download GradientFilter and its CMakeLists.txt file. Once the tarball GradientFilter.tar has been downloaded and extracted,
cd GradientFilter/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:
./GradientFilter
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.