[MCPE-14022] Covering roof of spawn chamber with bottom-half slabs severely reduces the spawn rate Created: 31/Mar/16  Updated: 13/Apr/17  Resolved: 13/Apr/17

Status: Resolved
Project: Minecraft (Bedrock codebase)
Component/s: None
Affects Version/s: 0.14.0, 0.14.1, 0.14.2, 0.14.3, 0.15.4, 1.0.2, 1.0.3
Fix Version/s: 1.0.6.52

Type: Bug
Reporter: PHO
Resolution: Fixed Votes: 3
Labels: entity-spawning, slab

Attachments: File Slabbled-Roof-Glitch.mcworld     PNG File chamber-A-inside.png     PNG File chamber-A.png     PNG File chamber-B-inside.png     PNG File chamber-B.png    
Issue Links:
Duplicate
is duplicated by MCPE-19950 Slabs let all light through Resolved
Relates
relates to MCPE-11112 Hostile mobs don't spawn underground ... Resolved
relates to MCPE-14467 Hostile mobs are spawning on/in trans... Resolved
relates to MCPE-16077 Mobs spawn everywhere Resolved
relates to MCPE-12422 Vertical distance is ignored by the h... Resolved
Confirmation Status: Confirmed
Platform: Tablet - iOS - iPad 3
CHK:
ADO: 56654

 Description   

Everyone knows that mobs cannot spawn on top of bottom-half slabs. But in this specific case mobs hardly spawn at all below solid opaque blocks with a bottom-half slab on top of it. This somewhat relates to MCPE-12422 and now-fixed MCPE-11112 but is clearly not the same.

Steps to reproduce:

  1. Build a 12x12x3 spawn chamber out of any kind of solid opaque blocks.
  2. Optionally place tripwire and redstone lamps to ease observing mobs inside it.
  3. Take 24 blocks away from it and wait 10 seconds or so.
  4. Observe that mobs start to spawn in the chamber.
  5. Now cover the roof of chamber with any kind of bottom-half slabs.
  6. Take 24 blocks away from it and wait for mobs again.
  7. Observe that the spawn rate has severely reduced. Now it takes several tens of minutes to spawn even a single mob.

What I expected:
Slabs on the roof do not affect the spawn rate at all.

Note that the inner height of spawn chamber needs to be 3 blocks or higher in order to trigger this bug. If it's only 2 blocks high, slabs don't affect the spawn rate as expected.



 Comments   
Comment by PHO [ 13/Apr/17 ]

Yes I confirmed it's been fixed.
Thank you rboxman for testing the bug

Comment by rboxman [ 13/Apr/17 ]

This may be fixed as it's listed in the 1.0.6 changelog. I tried OPs Chamber-B design (full blocks covered by half-slabs for the roof) and I'm getting spawns inside my enclosed room relatively quickly. I don't have a full size farm though so it would be good to get a second opinion here.

Comment by rboxman [ 28/Feb/17 ]

Related to the fact that half-slabs in Pocket Edition do not block light and it's still present in 1.0.3...

Comment by PHO [ 07/Feb/17 ]

Test world attached.

Comment by Michael Gill [ 29/Jan/17 ]

Confirmed in 1.0.2. Made Mumbo Jumbo's mob spawned design. Spawn rates very low to begin with but add a bottom half slab roof at any height and spawning halts completely.

Comment by AMAN4700 [ 18/Nov/16 ]

This is a bulk resolve of issues that haven't been updated to 0.16.0+ yet. Please comment below (To open the ticket) and update your affected versions. If you cannot reproduce the bug, please write in the comments so we can resolve it as "Cannot Reproduce". Thank You!

Comment by AMAN4700 [ 08/Aug/16 ]

Please respond and add the current version if you can reproduce this issue.

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