Rotten Zombie Spawner

Infinite zombies spawning to replace molerats at the Rotten Landfill location.

Sometimes, too many zombies is a bad thing. Like when said zombie horde crashes your game. This is unfortunately what was happening at the Rotten Landfill thanks to how the quest there worked in conjunction with animal spawn replacements.

The Issue

There is a quest used at the Rotten Landfill to stage a fight between a settler and some molerats. The idea is to have this fight continue until the player is close enough to witness it and potentially intervene.

The quest marks the settler as immortal and spawns a few molerats that are marked to re-spawn when killed. When the player gets within 6000 units the fight is triggered and will continue forever with the molerats continuously re-spawning as the immortal settler eventually kills them. When the player gets within 3000 units the fight becomes real in that the settler is mortal and the infinite re-spawns are stopped (and instead become X waves as described on the wiki).

When using the animal spawn replacement option via the Zombie Walkers holotape, these molerats are replaced by zombies. During that replacement, the molerat being replaced isn't just disabled (disappearing from view) but also killed. Since the molerat is killed, it triggers the quest to re-spawn the molerat which in turn gets killed and replaced with a zombie. This triggers the molerat to re-spawn again... well, you probably see where this infinite loop is going.

Why kill the replacement?

Good question. I knew some quests involve creatures that might be replaced by my mod. To avoid those quests getting stuck, I wanted to make sure they didn't end up waiting for a death event that would never arrive. The first example of this I can think of is the Sanctuary bloatfly quest with Codsworth.

So how do we fix Rotten Landfill?

The easy solution would have been to simply exclude the location from spawn replacements, but I'm too masochistic for that. Instead what I ended up doing is delaying the kill until the zombie that replaced the molerat was killed.

This was actually fairly straightforward to implement. At time of replacement, the creature being replaced is still disabled and I added a linked reference to the creature being replaced to the zombie that was replacing it with a new keyword. When that zombie died, I added code to check for that type of child linked ref and kill it also if present. Note that this only applies to the first zombie replacing that actor, so if you are using 2 for 1 replacements, the second zombie's death will do nothing to the replaced actor.

This approach not only solves the Rotten Landfill issue but also keeps quests from getting stuck. It should also be universally applicable for other re-spawns that might be used in other areas. Finally, it makes sense and flows better while you are playing the game. Now when you meet Codsworth in Sanctuary, you will search the neighborhood killing zombies instead of bloatflies instead of the quest starting out in a "I already searched the neighborhood" state.