configure Camera to use orthographic projection?

[lambertwx]

I am trying to configure the Camera (in the Open3DScene inside a SceneWidget) to use orthographic projection. According to the docs this should be possible using Camera.set_projection, but I get an error when I call it.

Here's my code:

import open3d.visualization.gui as gui
import open3d.visualization.rendering as rendering

gui.Application.instance.initialize()
window = gui.Application.instance.create_window("scenewidget", 1024, 1024)
widget = gui.SceneWidget()
widget.scene = rendering.Open3DScene(window.renderer)
bbox = open3d.geometry.AxisAlignedBoundingBox([-10, -10, -10],
                                                   [10, 10, 10])
fov_degs = 60
widget.setup_camera(fov_degs, bbox, [0, 0, 0])
widget.scene.camera.look_at([0,0,0],
                                [0, 50, 50],
                                [0, -1, 0])
widget.scene.camera.set_projection(rendering.Camera.Projection.Ortho, -10, 10, -10, 10, 1, 10)

Running open3d 0.16.1 on MacOS Big Sur 11.7.4, I get the runtime error in void filament::FCamera::setProjection(Camera::Projection, double, double, double, double, double, double):100 reason: Camera preconditions not met. Using default projection. and the projection remains perspective.

I tried removing the call to widget.setup_camera() but I still get the same result.

There is a ticket opened last year with this question #4862, but no activity, so I'm asking here.

[errissa]

@lambertwx I was able to reproduce this error and will look into it.

[manuel-koch]

I'm searching too for a solution to switch Open3DScene to use orthographic projection and can't find a working example.
Tried #3660 but this only yields runtime exceptions like
in void filament::FCamera::setProjection(Camera::Projection, double, double, double, double, double, double):100 reason: Camera preconditions not met. Using default projection.

Would be cool to find documentation or sample python code that actually shows how this can be achieved!
@lambertwx Can you provide any hint to get this done ?

[lee-deraud]

I had decent luck in v0.19 just setting FOV to a low value (I think 5 is the minimum) in 'setup_camera()'. It isn't perfect ortho, but it's visually good enough (YMMV). Something along the lines of:
widget.setup_camera(fov_degs, bbox, bbox.get_center())
and skip the 'set_proection()' call.