J for Jihad
In 'J for Jihad' - one of the films I made - there were various scenes/dream sequences where we see the protagonist crossing an 'invisible bridge' to reconnect with himself on the other side. The planks of the bridge may or may not appear under his feet, and sometimes he falls.
This is the opening scene of the film, where we see the main character, Jihad, falling towards us, and smashing his face on screen.
For crossing the bridge, the intended effect was to create the sensation of dangerously floating in a void (obviously inspired by Under The Skin and Stranger Things, but with zero budget!).
So we borrowed 3 benches, and asked the actor to stand/walk on them.
The rest was done in post.
To plan these shots, it was necessary to mock up an animatic. This was helpful in explaining to the crew what the action/scene may look like, and it also helped in imagining the edit and lighting equipment.