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

Support
1

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:

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())
2

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

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:

import vtkmodules.vtkRenderingOpenGL2
import vtkmodules.vtkRenderingVolumeOpenGL2
import vtkmodules.vtkRenderingContextOpenGL2
import vtkmodules.vtkRenderingFreeType