MC-252424Slimes spawn at light levels greater then 0 in Swamps
After the lighting change in 1.18, slimes in swamp biomes are the only mob to still spawn at light level 7 compared to light level 0 for all other Overworld hostile mobs.
How to Reproduce:
- Create a superflat world with the following preset:
- "minecraft:bedrock,127*minecraft:dirt,minecraft:mycelium,minecraft:brown_mushroom;minecraft:swamp;"
- Make sure 'Generate Structures' is set to OFF.
- The ground is high enough to be out of the range of slime chunks, but within the range of where slimes can spawn in swamps.
- Mycelium ensures the brown mushrooms don't break.
- Brown mushrooms emit a light level of 1 which, due to them blanketing the entire world, should prevent the spawning of all hostile mobs.
- Enter the world.
- Enter the command "/time set midnight".
- You should see nothing but slimes spawn, proving they have different spawning requirements in Swamps from other hostile mobs.
Environment
OS: Windows 10 Pro
Java: 17.0.3 16-bit
Created Issue:
Slimes Spawn at Light Level 7 in Swamps
After the lighting change in 1.18, slimes in swamp biomes are the only mob to still spawn at light level 7 compared to light level 0 for all mobs.
How to Reproduce:
- Create a superflat world with the following preset:
- "minecraft:bedrock,127*minecraft:dirt,minecraft:mycelium,minecraft:brown_mushroom;minecraft:swamp;"
- Make sure 'Generate Structures' is set to OFF.
- The ground is high enough to be out of the range of slime chunks.
- Mycelium ensures the brown mushrooms don't break.
- Brown mushrooms emit a light level of 1 which, due to them blanketing the entire world, should prevent the spawning of all hostile mobs.
- Enter the world.
- Enter the command "/time set midnight".
- You should see nothing but slimes spawn, proving they have different spawning requirements in Swamps from other hostile mobs.
- Note: Redstone torches and glow lichen won't work as nothing can spawn on either of those.
Environment
OS: Windows 10 Pro
Java: 17.0.3 16-bit
Changed Description:
After the lighting change in 1.18, slimes in swamp biomes are the only mob to still spawn at light level 7 compared to light level 0 for all mobs.
How to Reproduce:
- Create a superflat world with the following preset:
- "minecraft:bedrock,127*minecraft:dirt,minecraft:mycelium,minecraft:brown_mushroom;minecraft:swamp;"
- Make sure 'Generate Structures' is set to OFF.
- The ground is high enough to be out of the range of slime chunks.
- Mycelium ensures the brown mushrooms don't break.
- Brown mushrooms emit a light level of 1 which, due to them blanketing the entire world, should prevent the spawning of all hostile mobs.
- Enter the world.
- Enter the command "/time set midnight".
- You should see nothing but slimes spawn, proving they have different spawning requirements in Swamps from other hostile mobs.
- Note: Redstone torches and glow lichen won't work as nothing can spawn on either of those.
Changed Description:
After the lighting change in 1.18, slimes in swamp biomes are the only mob to still spawn at light level 7 compared to light level 0 for all mobs.
How to Reproduce:
- Create a superflat world with the following preset:
- "minecraft:bedrock,127*minecraft:dirt,minecraft:mycelium,minecraft:brown_mushroom;minecraft:swamp;"
- Make sure 'Generate Structures' is set to OFF.
- The ground is high enough to be out of the range of slime chunks, but within the range of where slimes can spawn in swamps.
- Mycelium ensures the brown mushrooms don't break.
- Brown mushrooms emit a light level of 1 which, due to them blanketing the entire world, should prevent the spawning of all hostile mobs.
- Enter the world.
- Enter the command "/time set midnight".
- You should see nothing but slimes spawn, proving they have different spawning requirements in Swamps from other hostile mobs.
Changed Description:
After the lighting change in 1.18, slimes in swamp biomes are the only mob to still spawn at light level 7 compared to light level 0 for all other Overworld hostile mobs.
How to Reproduce:
- Create a superflat world with the following preset:
- "minecraft:bedrock,127*minecraft:dirt,minecraft:mycelium,minecraft:brown_mushroom;minecraft:swamp;"
- Make sure 'Generate Structures' is set to OFF.
- The ground is high enough to be out of the range of slime chunks, but within the range of where slimes can spawn in swamps.
- Mycelium ensures the brown mushrooms don't break.
- Brown mushrooms emit a light level of 1 which, due to them blanketing the entire world, should prevent the spawning of all hostile mobs.
- Enter the world.
- Enter the command "/time set midnight".
- You should see nothing but slimes spawn, proving they have different spawning requirements in Swamps from other hostile mobs.
![[Mod] Anthony Cicinelli](../../../data/avatars/users/10122.svg){kind=small}
Added Category: Mob spawning
Removed Category: (Unassigned)
Changed Summary:
SlimesSpawn atLightLevel7in SwampsSlimes spawn at light levels greater then 0 in Swamps
This is intended. See tweet by [Mojang] Ulraf
Is there a possibility that Ulraf was thinking of only of slime chunk spawning when writing that tweet and swamp slime spawns are therefore an oversight?
To clarify: The light level changes only apply to block light (i.e., light emitted by blocks), not sky light (emitted by the sky, i.e. sun and moon). Those are two distinct values.
At night, there is a sky light level of 7. If the spawning requirements would include sky light, no mobs would spawn during night time at the surface, which is not desirable.
That's what Ulraf was talking about in his tweet.
Now, if they can still spawn in a block light level of >0 that might still be a bug.
Looks like I misinterpreted the tweet. I tested it out and was able to confirm that Slimes are spawning at a light level greater then 0.