[vtkusers] Why doesn't the intersection of the lines of a vtkCursor2D not set at the focal point?

[David Doria]

On Thu, Apr 8, 2010 at 9:52 PM, Xiaofeng Z <xf10036 at hotmail.com> wrote:
> Hi vtkUsers,
>
> The following is a program that place a vtkSphere and a vtkCursor2D in a
> rendering window.  My question is why the cursor 2d does not pass the center
> of the sphere, see attached image.
>
> int _tmain(int argc, _TCHAR* argv[])
> {
>     // create sphere geometry
>     vtkSphereSource *sphere = vtkSphereSource::New();
>     sphere->SetCenter(0.0, 0.0, 0.0);
>     sphere->SetRadius(1.0);
>     sphere->SetThetaResolution(18);
>     sphere->SetPhiResolution(18);
>
>     // map to graphics library
>     vtkPolyDataMapper *map = vtkPolyDataMapper::New();
>     map->SetInput(sphere->GetOutput());
>
>     // actor coordinates geometry, properties, transformation
>     vtkActor *actor = vtkActor::New();
>     actor->SetMapper(map);
>     actor->GetProperty()->SetColor(0,0,1); // sphere color blue
>
>     // renderers and render window
>     vtkRenderer *renA = vtkRenderer::New();
>     renA->SetViewport(0.0, 0.0, 1.0, 1.0);
>     vtkRenderWindow* win = vtkRenderWindow::New();
>     win->SetSize(300,300);
>     win->AddRenderer(renA);
>
>     // an interactor
>     vtkRenderWindowInteractor *iren = vtkRenderWindowInteractor::New();
>     iren->SetRenderWindow(win);
>
>     renA->SetBackground(1,1,1); // Background color white
>
>     renA->AddActor(actor);
>
>     // add a 2D cursor to each Renderer
>     vtkCursor2D* cursor = vtkCursor2D::New();
>     cursor->SetTranslationMode(1);
>     cursor->SetWrap(1);
>     cursor->SetModelBounds(-0.5, 0.5, -0.5, 0.5, 0.0, 0.0);
>     cursor->SetFocalPoint(0.0, 0.0, 0.0);
>     cursor->AllOff();
>     cursor->AxesOn();
>
>     vtkPolyDataMapper* mapper = vtkPolyDataMapper::New();
>     mapper->SetInput(cursor->GetOutput());
>     actor = vtkActor::New();
>     actor->SetMapper(mapper);
>     actor->GetProperty()->SetColor(1.0, 0.0, 0.0);
>
>     renA->AddActor(actor);
>
>     // render an image (lights and cameras are created automatically)
>     win->Render();
>
>     iren->Start();
>
>     return 0;
> }
>
>
> Xiaofeng Z

Hi Xiaofeng,

You need to create a new actor for the cursor:

i.e. replace this:

vtkPolyDataMapper* mapper = vtkPolyDataMapper::New();
mapper->SetInput(cursor->GetOutput());
actor = vtkActor::New();
actor->SetMapper(mapper);

with this:

vtkPolyDataMapper* mapper = vtkPolyDataMapper::New();
mapper->SetInput(cursor->GetOutput());
vtkActor* cursorActor = vtkActor::New();
cursorActor->SetMapper(mapper);

and then it works.

Here is the working code:
http://www.vtk.org/Wiki/VTK/Examples/Widgets/Cursor2D

Thanks,

David