Question: non-blocking windows

[schlegelp]

Quick question: I'd like to be able to interact with a scene programmatically from the Python shell (e.g. add/remove actors). Is there a way to show a non-blocking window?

Thanks!
Philipp

[skoudoro]

Hi @schlegelp,

Currently, it is not possible, but we are working on it. it seems we need to use vtkGenericRenderWindowInteractor.
Otherwise, if you do not need to show, you can have differents options:

• use offscreen option
• play with timer event like in this tutorial
• record some event and replay them (look at our tests)

hope it helps

[skoudoro]

Do you have another idea @Garyfallidis?

[Garyfallidis]

Hi Philip (@schlegelp),
Serge, is correct currently the window is blocking. However, you can have a nonblocking window if you use Qt. Here is an example of how you could do this

import sys
import time
import vtk
import threading
import numpy as np
from PyQt5 import QtCore, QtWidgets
from vtk.qt.QVTKRenderWindowInteractor import QVTKRenderWindowInteractor

class MainWindow(QtWidgets.QMainWindow):

    def __init__(self, parent = None):
        QtWidgets.QMainWindow.__init__(self, parent)

        self.frame = QtWidgets.QFrame()

        self.vl = QtWidgets.QVBoxLayout()
        self.vtkWidget = QVTKRenderWindowInteractor(self.frame)
        self.vl.addWidget(self.vtkWidget)

        self.ren = vtk.vtkRenderer()
        self.vtkWidget.GetRenderWindow().AddRenderer(self.ren)
        self.iren = self.vtkWidget.GetRenderWindow().GetInteractor()

        # Create source
        source = vtk.vtkSphereSource()
        source.SetCenter(0, 0, 0)
        source.SetRadius(5.0)

        # Create a mapper
        mapper = vtk.vtkPolyDataMapper()
        mapper.SetInputConnection(source.GetOutputPort())

        # Create an actor
        actor = vtk.vtkActor()
        actor.SetMapper(mapper)

        self.ren.AddActor(actor)

        self.ren.ResetCamera()

        self.frame.setLayout(self.vl)
        self.setCentralWidget(self.frame)

        self.show()
        self.iren.Initialize()

def calc_square(numbers, window):
    print("calculate square numbers")
    for n in numbers:
        time.sleep(1)
        print('square:', n*n)
        window.ren.GetActiveCamera().Azimuth(10)
        window.vtkWidget.Render()

if __name__ == "__main__":

    app = QtWidgets.QApplication(sys.argv)

    window = MainWindow()

    arr = np.random.rand(10)
    t1 = threading.Thread(target=calc_square, args=(arr, window))

    t1.start()

    sys.exit(app.exec_())

    t1.join()

We would love some help in allowing show and ShowManager to switch different backends including Qt. Let us know if you can help with a Qt backend.

[Garyfallidis]

In the meantime, we are also working on trying to figure out how to make the default window non-blocking. Not trivial.... but there is progress.

[schlegelp]

Thanks for the responses. I'll let you know if I come up with something useful!