Fortnite just held a Design Chat on Reddit explaining “Ghost Peeking” and the changes it got in the v5.10 update.
“Ghost Peeking” occurs when players fire over their cover without actually being seen by their enemy. This happens when players are crouching uphill, which is a factor in why the effect happens in the first place.
In the image below, the green line is supposed to be the bullet trace, while the yellow line is a traces from the centre of the player’s camera.

Since Fortnite’s animation system makes adjustments to position a player’s feet while they are standing on a slope, it sometimes causes the character to mesh farther down than intended.
In the latest update, a fix for this issue was made, allowing players to also be targeted while they are shooting at others. As of now, the bullet and camera traces look like this:

The designer who took part in Fortnite’s Design chat asked players to report any other issues with “Ghost Peeking” so that the design team could keep improving in that area.




