I did some more testing. It appears that if I regenerate the chunks in the new snapshot, there is still a fortress there, but it is in a much different configuration. Mob spawning seems to work fine on the new fortress though.
Is it possible that the part of the code that tells the mobs where to spawn, is attempting to spawn them based on what the configuration of the fortress would be if it were newly spawned? That would explain the Wither Skeleton you found, if the new fortress generation code places a bridge in the same place it would have been in the old version, the Skeletons should still spawn in that small section regardless of version.
(This is all speculation based on observation, I'm not actually looking at the code, I'm just guessing based on what I've seen and read. I could be way off base.)
Kirk Mernett
I did some more testing. It appears that if I regenerate the chunks in the new snapshot, there is still a fortress there, but it is in a much different configuration. Mob spawning seems to work fine on the new fortress though.
Is it possible that the part of the code that tells the mobs where to spawn, is attempting to spawn them based on what the configuration of the fortress would be if it were newly spawned? That would explain the Wither Skeleton you found, if the new fortress generation code places a bridge in the same place it would have been in the old version, the Skeletons should still spawn in that small section regardless of version.
(This is all speculation based on observation, I'm not actually looking at the code, I'm just guessing based on what I've seen and read. I could be way off base.)