Anti-aliasing issues with Python VTK and Qt

Support
1

The following Gist contains two simple VTK examples:

The qt_ex.py example runs VTK inside a Qt window, while the vtk_ex.py runs a pure VTK window. The problem I’m facing is that the Qt version has no anti-alias. See the following screenshots:

Qt version:

2020-01-30-133407_947x527_scrot
2020-01-30-133407_947x527_scrot947×527 2.15 KB

VTK version:

2020-01-30-133501_945x525_scrot
2020-01-30-133501_945x525_scrot945×525 5.7 KB

Why is this happening? How do I get the same anti-alias in the Qt version?

More information:

$ uname -a
Linux lnn183-linux 5.4.14-arch1-1 #1 SMP PREEMPT Thu, 23 Jan 2020 10:07:05 +0000 x86_64 GNU/Linux
$ pacman -Si vtk | grep Version
Version         : 8.2.0-9
$ glxinfo | head
name of display: :0
display: :0  screen: 0
direct rendering: Yes
server glx vendor string: NVIDIA Corporation
server glx version string: 1.4
server glx extensions:
    GLX_ARB_context_flush_control, GLX_ARB_create_context, 
    GLX_ARB_create_context_no_error, GLX_ARB_create_context_profile, 
    GLX_ARB_create_context_robustness, GLX_ARB_fbconfig_float, 
    GLX_ARB_multisample, GLX_EXT_buffer_age,
2

If the OpenGL context is being created by Qt, you might have to modify Qt’s default OpenGL pixel format before creating the widget. See https://doc.qt.io/qt-5/qglformat.html#setDefaultFormat

Here is some 100% untested code for you to try:

f = QGLFormat()
f.setSampleBuffers(True) # turn on antialiasing
QGLFormat.setDefaultFormat(f)
1 Like
3

Your 100% untested code was correct, thanks! :wink:

4

Hi Ian,
seems like I face the same problem.

I tried to run the sample with the snippet included by David Gobbi, but it doesn’t seem to work:

    from PyQt5.QtOpenGL import QGLFormat
    from PyQt5.QtWidgets import QApplication
    import vtk

    from vtkmodules.qt.QVTKRenderWindowInteractor import QVTKRenderWindowInteractor

    app = QApplication([])

    f = QGLFormat()
    f.setSampleBuffers(True)  # turn on antialiasing
    QGLFormat.setDefaultFormat(f)

    renderer = vtk.vtkRenderer()
    axes = vtk.vtkCubeAxesActor()
    axes.SetBounds(-.1, .1, -.1, .1, -.1, .1)
    axes.SetCamera(renderer.GetActiveCamera())
    axes.SetFlyModeToStaticTriad()
    renderer.AddActor(axes)

    widget = QVTKRenderWindowInteractor()
    widget.GetRenderWindow().AddRenderer(renderer)
    widget.SetInteractorStyle(vtk.vtkInteractorStyleTrackballCamera())
    widget.Initialize()
    widget.Start()
    widget.show()

    app.exec_()

Would this work on your machine or do I have to add the snippet with the QGLFormat somewhere else?