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  1. Minecraft: Java Edition
  2. MC-136549

Skylight / light updates FPS lag

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    Details

    • Type: Bug
    • Status: Resolved
    • Resolution: Duplicate
    • Affects Version/s: Minecraft 1.13.1
    • Fix Version/s: None
    • Labels:
      None
    • Environment:

      Windows 10 Pro - Java 8 Update 181 (64-bit)

    • Confirmation Status:
      Unconfirmed

      Description

      The bug

      This bug causes alot of light updates, dropping your FPS to 0 and most likely crashing your game.

      This has been used for around a year now on several servers, this causes players to crash their game.

      How to reproduce

      1. Create a new world (superflat, cheats on)
      2. Execute command: /fill ~20 ~200 ~-20 ~-20 ~200 ~20 stone
      3. Teleport yourself up to the platform. (/tp @a ~ ~205 ~)
      4. Place 2 observers facing into each other, make a hole 1 block away from the observer. (See screenshot for setup. the observers is to make a repeating redstone clock)
      5. Just place the piston so it pulls the block over the hole.
      6. Prepare yourself to see your FPS drop to 0.
          • IF YOU DONT HAVE A GOOD PC, YOUR GAME WILL CRASH *** 

       

      Code analysis

      The following is based on a decompiled version of Minecraft 1.12 using MCP940.

       

      The reason for this is that in the method

      net.minecraft.world.chunk.setBlockState(BlockPos, IBlockState),

      In this method you have this piece of code: this.relightBlock(i, j + 1, k);

      If you remove the '+ 1' the issue is fixed. (line: 657)

      ^ I'll attach a video with the '+ 1' and without the '+ 1'.

       

        Attachments

        1. 2018-08-29_04.15.51.png
          2018-08-29_04.15.51.png
          181 kB
        2. 2018-08-29_04.18.00.png
          2018-08-29_04.18.00.png
          540 kB
        3. MC-136549.mp4
          7.61 MB

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              • Assignee:
                Unassigned
                Reporter:
                Oval Oval
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                Dates

                • Created:
                  Updated:
                  Resolved: