Moving Cameras on Invisible Track

[Maymone]

I have noticed on some routes that invisible track is placed "flying" along the visible track, to support cameras that follow trains. They would behave like the Lineside cameras but moving. After trying a while with invisible track and some invisible loco-cameras, I still can't figure out how that's done. Any tips?
Thanks
TM

 

[martinvk]

If the invisible track is one long loop then then you wont need any junctions or signals so just tell the invisible locomotive to Drive. Adjust the camera to point in your desired direction. I like to use a balloon or a small airplane to make it easier to click on to get on board.