Ambush monsters gain hindsight

[Lillium]

Alternative title - 'Ambush' monsters can see me out of their arses, so long as I've previously fired my gun within earshot.

 

I have a section where two crowds of monsters are facing away from the player as they enter the room, set to ambush as I don't want the second crowd to attack when the first crowd is attacked. However, when I walked into the room, both crowds immediately notice me despite facing the other way.

 

I did a quick little test where I ran through the section twice - once (1) with their ambush flags set as normal, another (2) without. I noclipped/notargetted my way through to that spot:

 1 - Walk out of sight, turn off notarget. Walk over to behind the monsters. They do not alert, as expected, until I fire a gun.

 2 - Walk out of sight, turn off notarget. Walk over to behind the monsters. They do not alert, as expected. Walk back out of sight, fire my gun. They still do not alert. Again, walk back to behind the monsters - they now alert as soon as I'm behind them.

 

Is this normal doom behavior or a quirk of the port I'm using (gzdoom for testing at the moment, though the map is using a Boom format)?

I think I can do what I want with just soundproof linedefs, but still an interesting behavior I want to know if is supposed to be happening.

[Bauul]

Yep, this is the expected behavior.  Once an Ambush flagged monster is woken up, it remains dormant until the player enters any degree of its vision, not just the direction its facing. It's this way in vanilla Doom too.

 

You can read about it more here: https://doomwiki.org/wiki/Monster_behavior