# SGrid

VTKExamples/Cxx/StructuredGrid/SGrid

### Description¶

Creating a structured grid dataset of a semicylinder. Vectors are created whose magnitude is proportional to radius and oriented in tangential direction.

Other Languages

See (Python)

Question

If you have a simple question about this example contact us at VTKExamplesProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

### Code¶

SGrid.cxx

// This example shows how to manually create a structured grid.
// The basic idea is to instantiate vtkStructuredGrid, set its dimensions,
// and then assign points defining the grid coordinate. The number of
// points must equal the number of points implicit in the dimensions
// (i.e., dimX*dimY*dimZ). Also, data attributes (either point or cell)
// can be added to the dataset.
//
//
#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkDoubleArray.h>
#include <vtkHedgeHog.h>
#include <vtkMath.h>
#include <vtkNamedColors.h>
#include <vtkPointData.h>
#include <vtkPoints.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkStructuredGrid.h>

int main(int, char*[])
{
double x[3], v[3], rMin = 0.5, rMax = 1.0, deltaRad, deltaZ;
static int dims[3] = {13, 11, 11};

// Create the structured grid.
vtkSmartPointer<vtkStructuredGrid> sgrid =
vtkSmartPointer<vtkStructuredGrid>::New();
sgrid->SetDimensions(dims);

// We also create the points and vectors. The points
// form a hemi-cylinder of data.
vtkSmartPointer<vtkDoubleArray> vectors =
vtkSmartPointer<vtkDoubleArray>::New();
vectors->SetNumberOfComponents(3);
vectors->SetNumberOfTuples(dims[0] * dims[1] * dims[2]);
vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();
points->Allocate(dims[0] * dims[1] * dims[2]);

deltaZ = 2.0 / (dims[2] - 1);
deltaRad = (rMax - rMin) / (dims[1] - 1);
v[2] = 0.0;
for (auto k = 0; k < dims[2]; k++)
{
x[2] = -1.0 + k * deltaZ;
auto kOffset = k * dims[0] * dims[1];
for (auto j = 0; j < dims[1]; j++)
{
radius = rMin + j * deltaRad;
auto jOffset = j * dims[0];
for (auto i = 0; i < dims[0]; i++)
{
theta = i * vtkMath::RadiansFromDegrees(15.0);
x[0] = radius * cos(theta);
x[1] = radius * sin(theta);
v[0] = -x[1];
v[1] = x[0];
auto offset = i + jOffset + kOffset;
points->InsertPoint(offset, x);
vectors->InsertTuple(offset, v);
}
}
}
sgrid->SetPoints(points);
sgrid->GetPointData()->SetVectors(vectors);

// We create a simple pipeline to display the data.
vtkSmartPointer<vtkHedgeHog> hedgehog = vtkSmartPointer<vtkHedgeHog>::New();
hedgehog->SetInputData(sgrid);
hedgehog->SetScaleFactor(0.1);

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

vtkSmartPointer<vtkPolyDataMapper> sgridMapper =
vtkSmartPointer<vtkPolyDataMapper>::New();
sgridMapper->SetInputConnection(hedgehog->GetOutputPort());
vtkSmartPointer<vtkActor> sgridActor = vtkSmartPointer<vtkActor>::New();
sgridActor->SetMapper(sgridMapper);
sgridActor->GetProperty()->SetColor(colors->GetColor3d("Peacock").GetData());

// Create the usual rendering stuff
vtkSmartPointer<vtkRenderer> renderer = vtkSmartPointer<vtkRenderer>::New();
vtkSmartPointer<vtkRenderWindow> renWin =
vtkSmartPointer<vtkRenderWindow>::New();

vtkSmartPointer<vtkRenderWindowInteractor> iren =
vtkSmartPointer<vtkRenderWindowInteractor>::New();
iren->SetRenderWindow(renWin);

renderer->SetBackground(colors->GetColor3d("Beige").GetData());
renderer->ResetCamera();
renderer->GetActiveCamera()->Elevation(60.0);
renderer->GetActiveCamera()->Azimuth(30.0);
renderer->GetActiveCamera()->Dolly(1.25);
renWin->SetSize(640, 480);

// interact with data
renWin->Render();
iren->Start();

return EXIT_SUCCESS;
}


### CMakeLists.txt¶

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(SGrid)

find_package(VTK COMPONENTS
vtkCommonColor
vtkCommonCore
vtkCommonDataModel
vtkFiltersCore
vtkInteractionStyle
vtkRenderingContextOpenGL2
vtkRenderingCore
vtkRenderingFreeType
vtkRenderingGL2PSOpenGL2
vtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
message("Skipping SGrid: ${VTK_NOT_FOUND_MESSAGE}") return () endif() message (STATUS "VTK_VERSION:${VTK_VERSION}")
if (VTK_VERSION VERSION_LESS "8.90.0")
# old system
include(${VTK_USE_FILE}) add_executable(SGrid MACOSX_BUNDLE SGrid.cxx ) target_link_libraries(SGrid PRIVATE${VTK_LIBRARIES})
else ()
# include all components
add_executable(SGrid MACOSX_BUNDLE SGrid.cxx )
target_link_libraries(SGrid PRIVATE ${VTK_LIBRARIES}) # vtk_module_autoinit is needed vtk_module_autoinit( TARGETS SGrid MODULES${VTK_LIBRARIES}
)
endif ()


cd SGrid/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:

./SGrid


WINDOWS USERS

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