Objects tracked to camera track to the viewport camera at current frame instead of camera location at the frame it should be rendering

Question

I've created some text objects and to make sure they are always facing the camera I have them tracked to the camera with some constraints. I've tweaked the constraints until it looks fine in the Viewport and used individual renders here and there to double check the final product and it all looks fine. But when rendering the whole animation the text is suddenly in a different orientation. e.g. this is same frame, on the left individually rendered, on the right the frame created whilst rendering animation: The text is angled slightly differently and therefore the lighting is different as well.

In other cases the orientation is so different the text is barely even visible:

The text in my first image using the following constraints:

The text in my second image using the following constraints:

With some further fiddling I've figured out what seems to be happening. The constraints are locking to the location of the camera at the current frame selected in the viewport and are not updating to the new location of the camera during render animation. In the following blendfile if you set the Start to 930 and the Current to 930 and Render Animation (CTRL + F12) it will look normal. If you change the current frame to 450, but keep everything else the same you will see the text is twisted to face back toward where the camera is at frame 450.

On the left is with the current frame set to 930, on the right with the current frame set to 450:

It seems to defeat the purpose of constraints if they don't actually move with the constrained object whilst rendering the animation.

How do I make sure the constraints are actually updating as different frames are rendered? Or is there just a better way to make sure the text aligns properly with the camera?

Answer 1

I've found a solution to get the text to show up correctly with relatively little effort. By going to correct frame, and using Object > Rigid Body > Apply Transformation like so:

After doing that I could remove the problematic constraints but keep most of the effect I wanted, it did mean that for one shot the text doesn't follow the camera, but at least it wasn't completely reversed anymore, so I counted that as a win.

Since this doesn't actually solve the constraints not updating properly whilst rendering the animation I won't accept this answer, but as a temporary fix I thought it worth mentioning.