QVTKWidget + vtkPropPicker fails wrong coordinates

Question

I'm using vtkPropPicker with QVTKWidget, but it is not working: pick position is always (0,0,0) and actor is NULL when clicking on the white sphere. Clicking on the empty region however returns sometimes the sphereActor. Maybe is this a problem caused by the HiDPI resolution?

#include <vtkBorderWidget.h>
#include <vtkCommand.h>
#include <vtkPolyDataMapper.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkSmartPointer.h>
#include <vtkSphereSource.h>

#include <vtkInteractorStyleTrackballCamera.h>
#include <vtkPropPicker.h>

class MouseInteractorStyle2 : public vtkInteractorStyleTrackballCamera
{
public:
    static MouseInteractorStyle2* New();
    vtkTypeMacro(MouseInteractorStyle2, vtkInteractorStyleTrackballCamera);

    virtual void OnLeftButtonDown()
    {
      int *clickPos = this->GetInteractor()->GetEventPosition();

      vtkSmartPointer<vtkPropPicker>  picker = vtkSmartPointer<vtkPropPicker>::New();
      picker->Pick(clickPos[0], clickPos[1], 0, this->GetDefaultRenderer());

      double *pos = picker->GetPickPosition();
      std::cout << "Click at " << clickPos[0] << " " << clickPos[1] <<
                   ", pick position (world coordinates) is " << pos[0] << " " << pos[1] << " " << pos[2] <<
                   ", actor is " << picker->GetActor() << std::endl;

      vtkInteractorStyleTrackballCamera::OnLeftButtonDown();
    }
};

vtkStandardNewMacro(MouseInteractorStyle2);

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    vtkSmartPointer<vtkSphereSource> sphereSource = vtkSmartPointer<vtkSphereSource>::New();
    sphereSource->Update();

    vtkSmartPointer<vtkPolyDataMapper> sphereMapper = vtkSmartPointer<vtkPolyDataMapper>::New();
    sphereMapper->SetInputConnection(sphereSource->GetOutputPort());

    vtkSmartPointer<vtkActor> sphereActor = vtkSmartPointer<vtkActor>::New();
    sphereActor->SetMapper(sphereMapper);

    vtkSmartPointer<vtkRenderer> renderer = vtkSmartPointer<vtkRenderer>::New();
    renderer->AddActor(sphereActor);
    this->ui->qvtkWidget->GetRenderWindow()->AddRenderer(renderer);

    vtkSmartPointer<MouseInteractorStyle2> style = vtkSmartPointer<MouseInteractorStyle2>::New();
    style->SetDefaultRenderer(renderer);
    this->ui->qvtkWidget->GetInteractor()->SetInteractorStyle(style);
}

MainWindow::~MainWindow()
{
    delete ui;
}

mainwindow.h:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private:
    Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H

mainwindow.ui:

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>800</width>
    <height>600</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <layout class="QVBoxLayout" name="verticalLayout">
    <item>
     <widget class="QVTKWidget" name="qvtkWidget" native="true"/>
    </item>
   </layout>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>800</width>
     <height>22</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <customwidgets>
  <customwidget>
   <class>QVTKWidget</class>
   <extends>QWidget</extends>
   <header>QVTKWidget.h</header>
   <container>1</container>
  </customwidget>
 </customwidgets>
 <resources/>
 <connections/>
</ui>

main.cpp:

#include "mainwindow.h"

#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

Using VTK 8.2.0, Qt 5.13.1, macOS 10.14.6

Answer 1

Switching to QVTKOpenGLWidget fixed the issue.

Also, QVTKWidget is deprecated and will be removed soon.