[vtkusers] Picking in unstructured grids and in polydata

[Rob van Tol]

Dear vtkusers,

I have a problem with point picking in an unstructured grid and indicating 
the picked points in the renderwindow. If I apply the (nearly identical) 
code to polydata the picking and showing works fine. The codes were applied 
to a cube defined as polydata and as unstructrured grid.

Could it be that ugrid->Modify() does not work correctly? I use 
vtkLatestRelease(4.2).

If you have an answer to the problem, please let me know.
Both codes:

//For POLYDATA (wordks 
fine)-------------------------------------------------------------------------------------------------------------------

//--- VTK HEADERS ---//
#include "vtkActor.h"
#include "vtkRenderer.h"
#include "vtkRenderWindow.h"
#include "vtkRenderWindowInterActor.h"
//-------------
#include "vtkCommand.h"
#include "vtkIntArray.h"
#include "vtkPointData.h"
#include "vtkPointPicker.h"
#include "vtkPolyData.h"
#include "vtkPolyDataReader.h"
#include "vtkPolyDataMapper.h"
#include "vtkProperty.h"
//-------------


//--- GLOBALS   ---//
static vtkPolyData *polydata;
static vtkPointPicker *picker = vtkPointPicker::New();
static vtkIntArray *intarray = vtkIntArray::New();

//--- PICKCOMMAND ---//
class VcPick : public vtkCommand
{
public:
         static VcPick *New()
                 {
                         return new VcPick;
                 }
         void Delete()
                 {
                         delete this;
                 }
         virtual void Execute(vtkObject *caller, unsigned long, void*)
                 {
                         int pid = picker->GetPointId() ;
                         if ( pid >= 0 )
                         {
                                 cout << pid ;
                                 intarray = (vtkIntArray 
*)polydata->GetPointData()->GetScalars();
                                 if (intarray->GetValue(pid) == 0)
                                 {
                                         intarray->SetValue(pid,1);
                                         polydata->GetPointData()->SetScalars(intarray);
                                         polydata->Modified();
                                 }
                                 else
                                 {
                                         intarray->SetValue(pid,0);
                                         polydata->GetPointData()->SetScalars(intarray);
                                         polydata->Modified();
                                 }
                         }
                 }
};

void main()
{
//--- SOURCES ---//
         vtkPolyDataReader *datareader = vtkPolyDataReader::New();
                 datareader->SetFileName("Polydata.vtk");
         polydata = datareader->GetOutput();

//--- MAPPERS ---//
         vtkPolyDataMapper *datamapper = vtkPolyDataMapper::New();
                 datamapper->SetInput(polydata);

         vtkPolyDataMapper *geomapper = vtkPolyDataMapper::New();
                 geomapper->SetInput(polydata);

//--- ACTORS ---//
         vtkActor *dataactor = vtkActor::New();
                 dataactor->SetMapper(datamapper);
                 dataactor->GetProperty()->SetPointSize(10);
                 dataactor->GetProperty()->SetRepresentationToPoints();

         vtkActor *geoactor = vtkActor::New();
                 geoactor->SetMapper(geomapper);
                 geoactor->GetProperty()->SetColor(0,0,0);
                 geoactor->GetProperty()->SetRepresentationToWireframe();

//--- PICKING ---//
         VcPick *vcpick = VcPick::New();
                 picker->AddObserver(vtkCommand::EndPickEvent, vcpick);

//--- RENDERING ---//
         vtkRenderer *ren1 = vtkRenderer::New();
                 ren1->AddActor(geoactor);
                 ren1->AddActor(dataactor);
                 ren1->SetBackground(1,1,1);

     vtkRenderWindow *renwin = vtkRenderWindow::New();
                 renwin->AddRenderer(ren1);

         vtkRenderWindowInteractor *iren = vtkRenderWindowInteractor::New();
                 iren->SetRenderWindow(renwin);
                 iren->SetPicker(picker);

                 renwin->Render();
                 iren->Start();
}

//For UNSTRUCTURED (does not show the picked 
points)-------------------------------------------------------------------------------------------------------------------

//--- VTK HEADERS ---//
#include "vtkActor.h"
#include "vtkRenderer.h"
#include "vtkRenderWindow.h"
#include "vtkRenderWindowInterActor.h"
//-------------
#include "vtkCommand.h"
#include "vtkIntArray.h"
#include "vtkPointData.h"
#include "vtkPointPicker.h"
#include "vtkUnstructuredGrid.h"
#include "vtkUnstructuredGridReader.h"
#include "vtkDataSetMapper.h"
#include "vtkProperty.h"
//-------------


//--- GLOBALS   ---//
static vtkUnstructuredGrid *ugrid;
static vtkPointPicker *picker = vtkPointPicker::New();
static vtkIntArray *intarray = vtkIntArray::New();

//--- PICKCOMMAND ---//
class VcPick : public vtkCommand
{
public:
         static VcPick *New()
                 {
                         return new VcPick;
                 }
         void Delete()
                 {
                         delete this;
                 }
         virtual void Execute(vtkObject *caller, unsigned long, void*)
                 {
                         int pid = picker->GetPointId() ;
                         if ( pid >= 0 )
                         {
                                 intarray = (vtkIntArray 
*)ugrid->GetPointData()->GetScalars();
                                 if (intarray->GetValue(pid) == 0)
                                 {
                                         intarray->SetValue(pid,1);
                                         ugrid->GetPointData()->SetScalars(intarray);
                                         ugrid->Modified();
                                         cout <<" on" << endl;
                                 }
                                 else
                                 {
                                         intarray->SetValue(pid,0);
                                         ugrid->GetPointData()->SetScalars(intarray);
                                         ugrid->Modified();
                                         cout <<" off" << endl;
                                 }
                         }
                 }
};

void main()
{
//--- SOURCES ---//
         vtkUnstructuredGridReader *gridreader = 
vtkUnstructuredGridReader::New();
                 gridreader->SetFileName("UnstructuredGrid.vtk");
         ugrid = gridreader->GetOutput();

//--- MAPPERS ---//
         vtkDataSetMapper *datamapper = vtkDataSetMapper::New();
                 datamapper->SetInput(ugrid);

         vtkDataSetMapper *geomapper = vtkDataSetMapper::New();
                 geomapper->SetInput(ugrid);

//--- ACTORS ---//
         vtkActor *dataactor = vtkActor::New();
                 dataactor->SetMapper(datamapper);
                 dataactor->GetProperty()->SetPointSize(10);
                 dataactor->GetProperty()->SetRepresentationToPoints();

         vtkActor *geoactor = vtkActor::New();
                 geoactor->SetMapper(geomapper);
                 geoactor->GetProperty()->SetColor(0,0,0);
                 geoactor->GetProperty()->SetRepresentationToWireframe();

//--- PICKING ---//
         VcPick *vcpick = VcPick::New();
                 picker->AddObserver(vtkCommand::EndPickEvent, vcpick);


//--- RENDERING ---//
         vtkRenderer *ren1 = vtkRenderer::New();
                 ren1->AddActor(geoactor);
                 ren1->AddActor(dataactor);
                 ren1->SetBackground(1,1,1);

     vtkRenderWindow *renwin = vtkRenderWindow::New();
                 renwin->AddRenderer(ren1);

         vtkRenderWindowInteractor *iren = vtkRenderWindowInteractor::New();
                 iren->SetRenderWindow(renwin);
                 iren->SetPicker(picker);

                 renwin->Render();
                 iren->Start();
}


dr. R. van Tol
WTCM Gieterijcentrum
Technologiepark 9
B-9052 Zwijnaarde
tel.:0032 (0)9 2645704
fax:0032 (0)9 2645848
mailto:rob.vantol at wtcm.be 
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