Minimal working example for https://github.com/vispy/vispy/issues/1508

mwe.py

from vispy import scene
import numpy as np
from PySide2 import QtGui, QtWidgets, QtCore


class MyCanvas2D(scene.SceneCanvas):
    def __init__(self, vertices, faces):
        super(MyCanvas2D, self).__init__(keys=None, bgcolor="white")
        self.unfreeze()
        self.view = self.central_widget.add_view()
        self.view.camera = "panzoom"
        border = np.empty((faces.shape[0]*3, 2))
        for i in range(faces.shape[0]):
            tri = faces[i]
            border[3*i+0] = [tri[0], tri[1]]
            border[3*i+1] = [tri[1], tri[2]]
            border[3*i+2] = [tri[2], tri[0]]
        self.line = scene.visuals.Line(parent=self.view.scene, color="black",
                                       pos=vertices, connect=border)

        self.mesh = scene.visuals.Mesh(parent=self.view.scene, color="red", mode="lines",
                                       vertices=vertices + [0, 5], faces=faces)
        self.freeze()

class MyCanvas3D(scene.SceneCanvas):
    def __init__(self, vertices, faces):
        super(MyCanvas3D, self).__init__(keys=None, bgcolor="white")
        self.unfreeze()
        self.view = self.central_widget.add_view()
        self.view.camera = "arcball"

        self.mesh = scene.visuals.Mesh(parent=self.view.scene, vertices=vertices,
                                       faces=faces)
        self.freeze()


class MyWindow(QtWidgets.QMainWindow):
    def __init__(self):
        super(MyWindow, self).__init__(None)
        vertices = np.array([[0.537705,  0.20005],
                             [0.182211, -2.04804],
                             [-1.7101, -0.906589],
                             [2.49874, -1.04955],
                             [0.394538, -3.07266],
                             [-0.233476, -0.880998],
                             [0.5,  1.],
                             [1.4319, -1.16265]])

        faces = np.array([[4, 3, 7],
                          [0, 7, 3],
                          [7, 0, 5],
                          [2, 5, 0],
                          [1, 5, 2],
                          [5, 1, 7],
                          [7, 1, 4],
                          [2, 4, 1],
                          [0, 6, 2],
                          [3, 6, 0]])

        splitter = QtWidgets.QSplitter(QtCore.Qt.Horizontal)

        self.canvas2d = MyCanvas2D(vertices, faces)
        self.canvas2d.create_native()
        splitter.addWidget(self.canvas2d.native)

        self.canvas3d = MyCanvas3D(vertices, faces)
        self.canvas3d.create_native()
        splitter.addWidget(self.canvas3d.native)
        
        self.setCentralWidget(splitter)


if __name__ == "__main__":
    app = QtWidgets.QApplication([])
    win = MyWindow()
    win.show()
    app.exec_()