In my add-on, location_3d_to_region_2d in rare situations returns None. I looked in Blender API:
bpy_extras.view3d_utils.location_3d_to_region_2d(region , rv3d , coord , *** , default=None )
Saw that there is a 4th parameter
default which will be returned if
coord (3rd parameter) is behind the origin of a perspective view.
Could someone elaborate what it means that a coordinate is behind the origin of a perspective view? Thanks.