Скачать или смотреть Blender python animation driver for viewport position / rotation sync

Blender does not seem to support constraints that would allow following the viewport position / rotation out-of-the-box.

Though it's possible to view the scene through a camera and make the camera automatically follow the viewport, undoing actions would undo the camera position too, resulting in frustrating viewport jumps.

I found out that changes applied by animation drivers aren't undone, so it should be possible to copy the viewport position / rotation onto an arbitrary object: here it's an empty arrow named "ViewFollower".

In this proof of concept I perform multiple sculpt brush strokes on a cube and undo a few of them, while still keeping the ViewFollower in sync with the viewport position / rotation.

Because the viewport rotation is being returned as a quaternion but the "ViewFollower" rotation is being applied for each Euler coordinate separately, Python script support needs to be activated for quaternion - Euler conversion. This can be enabled after opening the file (recommended for security reasons) or globally in the load / save settings area (at your own risk).

Even though the drivers are getting properly registered, moving / rotating the viewport does not trigger them. To force that, a python script (here: main.py) must be executed once after opening the file to register periodic (here: every 0.1s) driver updates. Feel free to adjust the interval to your liking.

I consider this a proof of concept. I'm sure that registering the periodic updates can be done via GUI elements or even shortcuts later o, but it's only worth the effort f the approach will be confirmed to work for people that were looking for a solution to this problem.

Known issues:
If you undo too far, you may undo registering the periodic driver updater, but since registering will happen very early, I don't see a great risk down the line. In this example I was able to undo sculpt strokes 2-3 times without breaking it.
You need to know the index of the 3d viewport area and update the driver expressions accordingly. In my case it was index 3. It may depend on your particular workspace setup. A way to look specifically for the vist VIEW_3D type area has been included in the python script.
The rotation of the ViewFollower may appear mirrored to what you would have actually expected, though this can be either addressed with more vector math or by constraining another object to some negative axis of the ViewFollower.