[vtkusers] vtkPointPicker / vtkGlyph3D problem

[Allan James]

Hi Alberto,

I could not fix the problem with point picker not producing correct results. After much banging of head against wall I tried cellpicker instead which is now working correctly. I would love to know what I was doing wrong with point picker!

Below is some code snippets for using cellpicker to select a glyph generated using vtkGlyph3D. This code has been hacked a bit from a larger project so it's a bit messy and I havent tested it as is. However it should work by left-clicking on a glyph. 

If anyone has suggestions on making this code better, please let me know.


////////////////////////////////////////////////////////
// Make sure GeneratePointIdsOn() called on vtkGlyph3D
// This generates an array on the output dataset called 
// "InputPointIds" which generates pointIDs in the glyphs
// that match the original input pointIDs.
////////////////////////////////////////////////////////
_glyphs->GeneratePointIdsOn();

///////////////////////////////////////////
// Setup pick callback (ScenePickCallback)
///////////////////////////////////////////
_scenePickCallback = ScenePickCallback::New();
_scenePickCallback->actorToPick = _glyphActor;
_scenePickCallback->glyphsToPick = _glyphs;
_scenePickCallback->sceneRenderWindowInteractor = _sceneRenderWindowInteractor;
_sceneRenderWindowInteractor->GetInteractorStyle()->AddObserver(vtkCommand::LeftButtonReleaseEvent, _scenePickCallback);


class ScenePickCallback : public vtkCommand
{
public:
	static ScenePickCallback *New();
	virtual void Execute(vtkObject *caller, unsigned long eventId, void* data);

	vtkSmartPointer<vtkActor> actorToPick;
	vtkSmartPointer<vtkGlyph3D> glyphsToPick;
	vtkSmartPointer<vtkRenderWindowInteractor> sceneRenderWindowInteractor;

private:
	ScenePickCallback();
};

void ScenePickCallback::Execute(vtkObject *caller, unsigned long eventId, void* data)
{
	if(eventId == vtkCommand::LeftButtonReleaseEvent)
	{
		int pickPosition[2];
		sceneRenderWindowInteractor->GetEventPosition(pickPosition);

		sceneRenderWindowInteractor->GetPicker()->Pick(pickPosition[0], pickPosition[1], 0, sceneRenderer);

		vtkCellPicker *cellPicker = reinterpret_cast<vtkCellPicker*>(picker.GetPointer());
		if(cellPicker)
		{
			// Check if correct actor was picked
			if(cellPicker->GetActor() == actorToPick.GetPointer())
			{
				vtkDataArray *inputIds = glyphsToPick->GetOutput()->GetPointData()->GetArray("InputPointIds");

				if(inputIds)
				{
					vtkCell *cell = glyphsToPick->GetOutput()->GetCell(cellPicker->GetCellId());

					if(cell && cell->GetNumberOfPoints() > 0)
					{
						// get first PointId from picked cell
						vtkIdType inputId = cell->GetPointId(0);

						// get matching Id from "InputPointIds" array
						vtkIdType selectedPointId = inputIds->GetTuple1(inputId);

						if(selectedPointId >= 0)
						{
							// POINT PICKED!
							// selectedPointId = Picked PointID (original input points)
						}
					}
				}

			}
			else
			{
				// NONE PICKED
			}
		}
	}
}



Allan James
High Performance Computing & Research Support
Queensland University of Technology
(07) 3138 9264
ar.james at qut.edu.au
http://www.qut.edu.au/its/hpc
 
><(((º>  ._.·´¯`·..  >++(((º>  ._.·´¯`·..  >++(((º>
 

> -----Original Message-----
> From: Gomez, Alberto [mailto:alberto.gomez at kcl.ac.uk] 
> Sent: Friday, 30 April 2010 8:53 PM
> To: Allan James
> Cc: vtkusers at vtk.org
> Subject: Re: [vtkusers] vtkPointPicker / vtkGlyph3D problem
> 
> Hi all,
> 
> I am trying to select a vector from a vector field with the 
> mouse. The 
> vector field is a glyph of vectors and it is generated in the 
> following 
> way (1). Then I use a custom interaction (subclassing 
> vtkInteractionStyleTrackballCamera) so that I pick points 
> when I press 
> the mouse button (2). When I click the left button, a 
> callback (3) does 
> some processing. The problem is that the position I get does 
> not match 
> the real vector position (i.e. I plot a vector at the 3D point I get 
> with the picker through the method picker->GetPickPosition() 
> and it does 
> not match). Anyone has a clue on why? I have played around with the 
> tolerance with no success.
> 
> Another question, how can I get the point information (vector and 
> position) from the point id??
> 
> Thanks,
> 
> Alberto
> 
> 
> (1) Vector field generation :
> 
> //positions
>     vtkSmartPointer<vtkPoints> pts = 
> vtkSmartPointer<vtkPoints>::New();
>     pts->SetNumberOfPoints(num_pts);
> //directions
>     vtkSmartPointer<vtkDoubleArray> vecArr =   
> vtkSmartPointer<vtkDoubleArray>::New();
>     vecArr->SetNumberOfComponents(3);
>     vecArr->SetNumberOfTuples(num_pts);
>     for (int i = 0; i < num_pts; i++) {
>             pts->InsertNextPoint(positions[i][0], positions[i][1], 
> positions[i][2]);
>             float tuple[3] = {(float) directions[i][0] , (float) 
> directions[i][1], (float) directions[i][2]};
>             vecArr->InsertNextTuple(tuple);
>       }
> 
> // put vectors and positions into a grid which will be the 
> glyph's input
>     vtkSmartPointer<vtkUnstructuredGrid> uGrid = vtkSmartPointer< 
> vtkUnstructuredGrid>::New();
>     uGrid->SetPoints(pts);
>     uGrid->GetPointData()->SetVectors(vecArr);
> 
>  // glyph construction
>     vtkSmartPointer<vtkArrowSource> arrow =   
> vtkSmartPointer<vtkArrowSource>::New();
>     vtkSmartPointer<vtkGlyph3D> glyph = 
> vtkSmartPointer<vtkGlyph3D>::New();
>     glyph->SetInput(uGrid);
>     glyph->SetSource(arrow->GetOutput());
>     glyph->SetScaleModeToScaleByVector();
>     glyph->GeneratePointIdsOn();
> //Mapper and actor
>     vtkSmartPointer<vtkPolyDataMapper> gMapper = 
> vtkSmartPointer<vtkPolyDataMapper>::New();
>     gMapper->SetInput(glyph->GetOutput());
>     gMapper->ScalarVisibilityOff();
>     gMapper->SetScalarRange(uGrid->GetScalarRange());
> 
> vtkSmartPointer<vtkActor> gactor = vtkSmartPointer<vtkActor>::New();
>     gactor->SetMapper(gMapper);
>     gactor->GetProperty()->SetColor(color);
>     ren->AddActor(gactor);
> 
> (2) Detail of my subclass for custom interactor style:
> virtual void OnLeftButtonDown()
>     {
>          if (this->Interactor->GetControlKey() ){
>                  int* pos = this->GetInteractor()->GetEventPosition();
>                 pointPicker->Pick(pos[0], pos[1], 0, 
> this->GetDefaultRenderer());
>         } else{
> 
>             vtkInteractorStyleTrackballCamera::OnLeftButtonDown();
>         }
>     }
> 
> (3)  Callback class (detail)
> 
> // Callback thats get called for a picking event.
> class PickCallback : public vtkCommand
> {
>   public:
>     static PickCallback* New()
>     {
>      return new PickCallback();
>     }
> 
>     void Execute(vtkObject* caller, unsigned long eventId, 
> void* callData)
>     {
>       vtkPointPicker *picker = static_cast< vtkPointPicker* >(caller);
>       if(picker->GetPointId() < 1)
>       {
>       // Nothing is picked.
>       }
>       else
>       {
>         double* pos = picker->GetPickPosition();
>      std::cout << pos[0]<< ","<< pos[1]<< ","<< pos[2]<< std::endl;
> 
>         actor = generateVectorActor(picker);
> 
> 
>         ren->AddViewProp(actor);
> 
> 
>       }
> 
> 
> 
>     }
> 
> Allan James wrote:
> > Hi all,
> >
> > I have an issue with code that is using vtkPointPicker to 
> pick points displayed using vtkGlyph3D.
> >
> > Now I have the picking working great for most of the glyphs 
> - using vtkGlyph3D->GeneratePointIdsOn(); and I am able to 
> select glyphs and display a sphere at the selected glyph location.
> >
> > My problem is that while this works perfectly 99% of the 
> time - there are certain glyphs that are either very 
> difficult to pick (sometimes impossible it seems) or I have 
> to click about 20 pixels or so above or next to the glyph for 
> the pick to work. Has anyone seen this issue and/or can suggest a fix?
> >
> > Why would picking work perfectly for most glyphs but not 
> for some others - when all of the glyphs are generated from 
> the same simple pointset using the same vtkGlyph3D filter?
> >
> > Any help would be muchly appreciated - thanks
> >
> > Allan James
> > High Performance Computing & Research Support
> > Queensland University of Technology
> > (07) 3138 9264
> > ar.james at qut.edu.au<mailto:ar.james at qut.edu.au>
> > http://www.qut.edu.au/its/hpc
> >
> >   
> >> <(((º>  ._.·´¯`·..  >++(((º>  ._.·´¯`·..  >++(((º>
> >>     
> >
> >
> >   
> 
> 
> -- 
> 
> Alberto Gómez
> 
> /Division of Imaging Sciences
> The Rayne Institute
> 4th Floor, Lambeth Wing
> St Thomas' Hospital
> London SE1 7EH /
> 
> phone: +44 (0) 20 718 88364
> email: alberto.gomez at kcl.ac.uk <mailto:alberto.gomez at kcl.ac.uk>
> 
>