If you have a PVP server and keep getting reports that players are shooting through trees or bushes in situations where they shouldn't be able to see, this is why.

Some AMD graphics cards/drivers are causing rendering issues on servers and players are not seeing the foilage, leaves on trees, bushes, grass, etc. I have made a mod for the Arma 3 community to temporarily fix this issue. This mod simply disables the ATOC video setting in the menu by default for anyone who uses this pbo. I am offering this pbo free to the community to use in their own modpacks to fix this issue until AMD resolves the problem, etc This issue has been acknowledged by BI and I have linked a thread on reddit on the workshop page where players discuss this problem on a widescale.

ATOC fix for AMD Graphics Cards not rendering foilage