# Frozen renderer and when using vtk in PySide6 when only importing used vtkmodules

**URL:** https://discourse.vtk.org/t/frozen-renderer-and-when-using-vtk-in-pyside6-when-only-importing-used-vtkmodules/15531
**Category:** Support
**Created:** [April 22, 2025, 8:15am UTC](https://discourse.vtk.org/t/frozen-renderer-and-when-using-vtk-in-pyside6-when-only-importing-used-vtkmodules/15531 "2025-04-22T08:15:36Z")
**Posts on this page:** 3
**Page:** 1

<div class="post-metadata">

### Author: ![rdbrn](https://discourse.vtk.org/user_avatar/discourse.vtk.org/rdbrn/32/5627_2.png) [@rdbrn](https://discourse.vtk.org/u/rdbrn)
#### Post date: [April 22, 2025, 8:15am UTC](https://discourse.vtk.org/t/frozen-renderer-and-when-using-vtk-in-pyside6-when-only-importing-used-vtkmodules/15531/1 "2025-04-22T08:15:36Z")

</div>

When I execute the script below I get a qt window with a non-responsive vtk display.  
It can be solved by enabling the “import vtk” line.

using:

- Windows 11
- Python 3.12
- vtk 9.4.1
- pyside6-essentials 6.8.2.1

Reproduce:

```python
import sys

# import vtk # <-- enable this to fix the import error

from PySide6.QtWidgets import QApplication, QMainWindow, QFrame, QVBoxLayout

from vtkmodules.qt.QVTKRenderWindowInteractor import QVTKRenderWindowInteractor
from vtkmodules.vtkFiltersSources import vtkCubeSource
from vtkmodules.vtkRenderingCore import vtkRenderer, vtkActor, vtkPolyDataMapper

class CubeViewer(QMainWindow):
    def __init__ (self, parent=None):
        super(). __init__ (parent)
        self.setWindowTitle("VTK Cube Viewer")
        self.resize(800, 600)

        # Create central frame
        self.frame = QFrame()
        self.layout = QVBoxLayout()
        self.frame.setLayout(self.layout)
        self.setCentralWidget(self.frame)

        # Create VTK widget
        self.vtk_widget = QVTKRenderWindowInteractor(self.frame)
        self.layout.addWidget(self.vtk_widget)

        # Create renderer and render window
        self.renderer = vtkRenderer()
        self.renderer.SetBackground(0.2, 0.2, 0.3) # Dark blue-gray background
        self.vtk_widget.GetRenderWindow().AddRenderer(self.renderer)

        # Initialize interactor
        self.interactor = self.vtk_widget.GetRenderWindow().GetInteractor()

        # Create cube
        self.create_cube()

        # Set camera position
        self.renderer.ResetCamera()
        camera = self.renderer.GetActiveCamera()
        camera.Elevation(30)
        camera.Azimuth(30)
        camera.Zoom(0.8)

        # Start interactor
        self.interactor.Initialize()

    def create_cube(self):
        # Create a cube source
        cube_source = vtkCubeSource()
        cube_source.SetXLength(1.0)
        cube_source.SetYLength(1.0)
        cube_source.SetZLength(1.0)
        cube_source.SetCenter(0.0, 0.0, 0.0)
        cube_source.Update()

        # Create a mapper
        mapper = vtkPolyDataMapper()
        mapper.SetInputConnection(cube_source.GetOutputPort())

        # Create an actor
        actor = vtkActor()
        actor.SetMapper(mapper)
        actor.GetProperty().SetColor(1.0, 0.6, 0.0) # Orange color
        actor.GetProperty().SetAmbient(0.3)
        actor.GetProperty().SetDiffuse(0.7)
        actor.GetProperty().SetSpecular(0.5)
        actor.GetProperty().SetSpecularPower(20)

        # Add actor to renderer
        self.renderer.AddActor(actor)

    def closeEvent(self, event):
        # Properly clean up VTK interactor on window close
        self.vtk_widget.close()
        super().closeEvent(event)

if __name__ == " __main__":
    app = QApplication(sys.argv)
    window = CubeViewer()
    window.show()
    sys.exit(app.exec())

```

---

<div class="post-metadata">

### Author: ![dgobbi](https://discourse.vtk.org/user_avatar/discourse.vtk.org/dgobbi/32/18_2.png) [@dgobbi](https://discourse.vtk.org/u/dgobbi)
#### Post date: [April 22, 2025, 4:24pm UTC](https://discourse.vtk.org/t/frozen-renderer-and-when-using-vtk-in-pyside6-when-only-importing-used-vtkmodules/15531/2 "2025-04-22T16:24:12Z")

</div>

When interaction fails, it’s sometimes because the RenderingUI module isn’t imported. Try adding this to your imports:

```python
import vtkmodules.vtkRenderingUI

```

But since this should already be imported by vtkmodules.qt.QVTKRenderWindowInteractor, it might not actually be the missing piece. Calling `import vtk` imports all the VTK extension modules, so there’s some guesswork involved in figuring out which one is needed. But often it’s vtkRenderingUI and/or one of these, which you can try one at a time and then together:

```python
import vtkmodules.vtkRenderingOpenGL2
import vtkmodules.vtkRenderingVolumeOpenGL2
import vtkmodules.vtkRenderingContextOpenGL2
import vtkmodules.vtkRenderingFreeType

```

---

<div class="post-metadata">

### Author: ![rdbrn](https://discourse.vtk.org/user_avatar/discourse.vtk.org/rdbrn/32/5627_2.png) [@rdbrn](https://discourse.vtk.org/u/rdbrn)
#### Post date: [May 8, 2025, 11:13am UTC](https://discourse.vtk.org/t/frozen-renderer-and-when-using-vtk-in-pyside6-when-only-importing-used-vtkmodules/15531/3 "2025-05-08T11:13:34Z")

</div>

Adding

```auto
import vtkmodules.vtkRenderingOpenGL2 

```

was the solution. Thanks!