SceneWidget() not updating until zoom in/out

[otretas]

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Checklist

• [x] I have searched for similar issues.
• [ ] For Python issues, I have tested with the [latest development wheel]
• [x] I have checked the release documentation and the latest documentation (for master branch).

The Issue

When launching the application, SceneWidget() does not draw objects in the scene unless you manually zoom in or out on the scene... At start:

After zooming in and out once it is properly displayed:

I tried to force_redraw() after adding the object but still have the same problem.

To Reproduce the Issue

import open3d as o3d
import numpy as np
import open3d.visualization.gui as gui
import open3d.visualization.rendering as rendering

class SeamSelector:
    def __init__(self):
        self.window = gui.Application.instance.create_window("asds", 800, 650)
        w = self.window
        em = w.theme.font_size
        _y = 500
        
        # Create renderer
        self.widget3d = gui.SceneWidget()
        self.widget3d.scene = rendering.Open3DScene(w.renderer)
        self.widget3d.set_view_controls(gui.SceneWidget.Controls.ROTATE_CAMERA)
        self.widget3d.scene.set_background([0.4, 0.4, 0.4, 1])
        bbox = o3d.geometry.AxisAlignedBoundingBox()
        self.widget3d.setup_camera(10.0, bbox, np.array([0.0,0.0,0.0]))
        self.widget3d.scene.camera.look_at([0, 0, 0], [0, 0, 19000], [0, 0, 1])
        self.widget3d.frame = gui.Rect(0, 0,
                                       w.content_rect.width, _y)
        # Create layout
        layout = gui.Vert(0, gui.Margins(0.5 * em, 0.5 * em, 0.5 * em,
                                         0.5 * em))
        layout.frame = gui.Rect(0, _y, 
                                w.content_rect.width, w.content_rect.height)
        #layout.add_child(self.widget3d)
        
        # Label
        self._label = gui.Label("Lorem ipsum dolor")
        self._label.text_color = gui.Color(1.0, 0.5, 0.0)
        
        layout.add_child(self._label)

        # Create a progress bar. It ranges from 0.0 to 1.0.
        self._progress = gui.ProgressBar()
        self._progress.value = 0.25  # 25% complete
        self._progress.value = self._progress.value + 0.08  # 0.25 + 0.08 = 33%
        prog_layout = gui.Horiz(em)
        prog_layout.add_child(gui.Label("Progress..."))
        prog_layout.add_child(self._progress)
        layout.add_child(prog_layout)

        # Create a slider. It acts very similar to NumberEdit except that the
        # user moves a slider and cannot type the number.
        slider = gui.Slider(gui.Slider.INT)
        slider.set_limits(5, 13)
        slider.set_on_value_changed(self._on_slider)
        layout.add_child(slider)

        # Create a text editor. The placeholder text (if not empty) will be
        # displayed when there is no text, as concise help, or visible tooltip.
        tedit = gui.TextEdit()
        tedit.placeholder_text = "Edit me some text here"
        # on_text_changed fires whenever the user changes the text (but not if
        # the text_value property is assigned to).
        tedit.set_on_text_changed(self._on_text_changed)
        # on_value_changed fires whenever the user signals that they are finished
        # editing the text, either by pressing return or by clicking outside of
        # the text editor, thus losing text focus.
        tedit.set_on_value_changed(self._on_value_changed)
        layout.add_child(tedit)

        # Quit button. (Typically this is a menu item)
        button_layout = gui.Horiz()
        ok_button = gui.Button("Ok")
        ok_button.set_on_clicked(self._on_ok)
        button_layout.add_stretch()
        button_layout.add_child(ok_button)
        layout.add_child(button_layout)

        # We're done, set the window's layout
        w.add_child(self.widget3d)
        w.add_child(layout)
        self.construct()
        
    def construct(self):
          
        # Now add a base beneath the object
        mesh_box = o3d.geometry.TriangleMesh.create_box(width=3000.0,
                                                    height=3000.0,
                                                    depth=1.0)
        mesh_box.compute_vertex_normals()
        mesh_box.translate(np.array([-1500,-1500,-3.0]))
        mesh_box.paint_uniform_color([0.3, 0.6, 1])
        mat = rendering.MaterialRecord()
        mat.shader = "defaultLit"
        self.widget3d.scene.add_geometry('sds', mesh_box, mat)

    def _on_slider(self, new_val):
        self._progress.value = new_val / 20.0

    def _on_text_changed(self, new_text):
        print("edit:", new_text)

    def _on_value_changed(self, new_text):
        print("value:", new_text)

    def _on_ok(self):
        gui.Application.instance.quit()

def main():
    gui.Application.instance.initialize()
    SeamSelector()
    gui.Application.instance.run()


if __name__ == "__main__":
    main()