I would like to introduce you to a 17 years old issue that exists across the whole Arma series, A3 included. It is one of the oldest Real Virtuality engine bug and it has not been addressed since OFP release back in 2001. I wish this post could reach BI devs so one day the problem would finally be solved. Arma3 is ahead of its final roadmap that will lead to its EOL (End-Of-Life). While there were other priorities across the development cycle in recent years, now it seems to be the right time to take care of it.   A bug/issue:
  I have recorded a short and entertaining video that explains what it is all about:
  The issue has already been mentioned in a number of A3 Feedback Tracker tickets: Fallen Trees Have No Collision Fallen objects have no collision detection with characters or bullets. Ai see through fallen vegetation and objects   Pointing out some interesting comments/notes from these tickets: Keeping Main Geometry (Geometry) for fallen static objects may negatively influence behaviour of AI (especially AI drivers). Vehicles may not be able to drive through / will collide with   the fallen objects. Lack of geometries for fallen static objects is performance-friendly.   My answers/suggestions to the aforementioned remarks: If Main Geometry of fallen static objects causes improper behaviour of AI or vehicles collide with them, then Main Geometry should be ignored. However, Fire Geometry and View Geometry should be kept to provide basic feature of cover & concealment. Undeniably. However, performance-wise argument could make sense back in OFP times, not in 2018. Unnoticeable performance boost is totally overshadowed by disadvantages the issue introduces into the game (especially for PvE scenarios).
      'Line of succession of the Arma series' - my report about the bug in OFP/CWA environment that precedes this thread