In some cases when:
* the viewport was in the camera mode
* the camera was ortho
* the view was not fitting (as oppose to use HOME)
region_2d_to_origin_3d would misbehave (and consequently region_2d_to_location_3d).
Sample addon to test it:
```
import bpy
from bpy_extras.view3d_utils import (
region_2d_to_location_3d,
)
from mathutils import (
Vector,
)
class MoveXYOperator(bpy.types.Operator):
"""Translate the view using mouse events"""
bl_idname = "view3d.move_xy"
bl_label = "Move XY"
@classmethod
def poll(cls, context):
return context.object
def modal(self, context, event):
if event.type == 'MOUSEMOVE':
self.move(context, event)
elif event.type in {'LEFTMOUSE', 'RIGHTMOUSE', 'ESC'}:
return {'FINISHED'}
return {'RUNNING_MODAL'}
def invoke(self, context, event):
if context.space_data.type == 'VIEW_3D':
self.ob = context.object
context.window_manager.modal_handler_add(self)
return {'RUNNING_MODAL'}
else:
self.report({'WARNING'}, "Active space must be a View3d")
return {'CANCELLED'}
def move(self, context, event):
xy = region_2d_to_location_3d(
context.region,
context.space_data.region_3d,
(event.mouse_region_x, event.mouse_region_y),
Vector(),
).xy
self.ob.location.xy = xy
def register():
bpy.utils.register_class(MoveXYOperator)
def unregister():
bpy.utils.unregister_class(MoveXYOperator)
if __name__ == "__main__":
register()
```
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