Modifying the polyData points/vertices in VTK - c++

Question

I'm trying to use VTK to change points, i.e. I am changing coordinates (x,y,z) by a (+1/-1) value. I am reading an .OBJ file and then accessing the points of a model and when I am trying to visualise the changes in the model the RenderWindow doesnt show anything. Below is my code:-
vtkSmartPointer<vtkOBJReader> reader = vtkSmartPointer<vtkOBJReader>::New();
reader->SetFileName(filename.c_str());
reader->Update();
vtkSmartPointer<vtkPolyData> polyData = reader->GetOutput();
polyData->Update();
Point3d point;
std::vector<Point3d> vertices;
double p[3];
vtkPoints* points = vtkPoints::New();
vtkDoubleArray* pcoord = vtkDoubleArray::New();
pcoord->SetNumberOfComponents(3);
pcoord->SetNumberOfTuples(polyData->GetNumberOfPoints());
for(vtkIdType i = 0; i < polyData->GetNumberOfPoints(); i++)
{
polyData->GetPoint(i,p);
p[0] +=1;
p[1] +=1;
p[2] +=1;
pcoord->SetTuple(i, p);
}
points->SetData(pcoord);
polyData->SetPoints(points);
polyData->Modified();
//Visualize Code
vtkSmartPointer<vtkPolyDataMapper> mapper = vtkSmartPointer<vtkPolyDataMapper>::New();
mapper->SetInputConnection(reader->GetOutputPort());
vtkSmartPointer<vtkActor> actor = vtkSmartPointer<vtkActor>::New();
actor->SetMapper(mapper);
vtkSmartPointer<vtkRenderer> renderer = vtkSmartPointer<vtkRenderer>::New();
renderer->AddActor(actor);
vtkRenderWindow* renderWindow = vtkRenderWindow::New();
renderWindow->AddRenderer(renderer);
vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor = vtkSmartPointer<vtkRenderWindowInteractor>::New();
renderWindowInteractor->SetRenderWindow(renderWindow);
renderWindowInteractor->Initialize();
renderWindowInteractor->Start();
I am new to this 3D and VTK stuff, Please check where I am missing since I want to change the coordinates of each vertex (x,y,z). Do I need to further change something else as well?
Many Thanks.

Answer 1

First thing, you have alignment issues in the code that you included in your question. I believe you are missing a for loop too. (where is "i" defined?)
The major issue is that you are not rendering polyData at all. The only thing you are rendering is what is in the .obj file. Evident from this line:
mapper->SetInputConnection(reader->GetOutputPort());
In order to render polyData replace the above line with:
mapper->SetInputData(polyData);
This assumes polyData was created correctly. I can't easily tell this from the code you provided.
Here is an example that may help.