Axes and camera widgets in a Qt render window

Jellby · September 12, 2025, 9:22am

Using vtkCameraOrientationWidget or vtkOrientationMarkerWidget works fine on a “barebones” Python script:

#!/usr/bin/env python3

import vtk

renderer = vtk.vtkRenderer()
render_window = vtk.vtkRenderWindow()
render_window.AddRenderer(renderer)
render_window_interactor = vtk.vtkRenderWindowInteractor()
render_window_interactor.SetRenderWindow(render_window)
render_window_interactor.GetInteractorStyle().SetCurrentStyleToTrackballCamera()

sphere_source = vtk.vtkSphereSource()

mapper = vtk.vtkPolyDataMapper()
mapper.SetInputConnection(sphere_source.GetOutputPort())

actor = vtk.vtkActor()
actor.SetMapper(mapper)

renderer.AddActor(actor)

cow = vtk.vtkCameraOrientationWidget()
cow.SetParentRenderer(renderer)
cow.On()

axes = vtk.vtkAxesActor()
om = vtk.vtkOrientationMarkerWidget()
om.SetOrientationMarker(axes)
om.SetInteractor(render_window_interactor)
om.On()

renderer.ResetCamera()

render_window.Render()
render_window_interactor.Start()

But trying to do the same in a Qt environment (PyQt5) does not display the widgets:

#!/usr/bin/env python3

import sys
import vtk
from PyQt5 import Qt
from vtk.qt.QVTKRenderWindowInteractor import QVTKRenderWindowInteractor

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        self.centralWidget = Qt.QWidget(MainWindow)
        self.gridlayout = Qt.QGridLayout(self.centralWidget)
        self.vtkWidget = QVTKRenderWindowInteractor(self.centralWidget)
        self.gridlayout.addWidget(self.vtkWidget, 0, 0, 1, 1)
        MainWindow.setCentralWidget(self.centralWidget)

class SimpleView(Qt.QMainWindow):
    def __init__(self, parent=None):
        Qt.QMainWindow.__init__(self, parent)
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)

        renderer = vtk.vtkRenderer()
        self.ui.vtkWidget.GetRenderWindow().AddRenderer(renderer)
        render_window_interactor = self.ui.vtkWidget.GetRenderWindow().GetInteractor()
        render_window_interactor.GetInteractorStyle().SetCurrentStyleToTrackballCamera()

        sphere_source = vtk.vtkSphereSource()

        mapper = vtk.vtkPolyDataMapper()
        mapper.SetInputConnection(sphere_source.GetOutputPort())

        actor = vtk.vtkActor()
        actor.SetMapper(mapper)

        renderer.AddActor(actor)

        cow = vtk.vtkCameraOrientationWidget()
        cow.SetParentRenderer(renderer)
        cow.On()

        axes = vtk.vtkAxesActor()
        om = vtk.vtkOrientationMarkerWidget()
        om.SetOrientationMarker(axes)
        om.SetInteractor(render_window_interactor)
        om.On()

        renderer.ResetCamera()

        self.iren = render_window_interactor

if __name__ == "__main__":
    app = Qt.QApplication(sys.argv)
    window = SimpleView()
    window.show()
    window.iren.Initialize()
    sys.exit(app.exec_())

Am I doing something wrong or are they just not compatible?