The 126.96.36.199 beta introduced scaled instant despawn distances based on a world's simulation distance setting. For simulation distance 4 the instant despawn radius was reduced from 54 blocks (the previous radius since 188.8.131.52 beta) to 44 blocks, presumably in order to ensure that non-persistent mobs are never saved in unloaded chunks (since
MCPE-78840 is WAI). However, the spawning area still extends to 54 blocks from the player. This results in spawns between r44 and r54 being immediately despawned. This wastes processing power in an endless loop of pointless activity, and it is also visually unpleasant.
- Set simulation distance to 4 and turn on mob spawning.
- Stand in a flat area.
- Look toward the distance.
You see mobs spawn and wander around, only disappearing when they wander away from you. Beyond the line where wandering mobs disappear, you see no mobs at all.
Beyond the line where wandering mobs disappear, you regularly see new mobs appear then immediately disappear.