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  1. Minecraft: Java Edition
  2. MC-168419

Massive frame drops caused by light update while crossing certain chunks

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    • Icon: Bug Bug
    • Resolution: Duplicate
    • None
    • 1.15.1
    • None
    • Confirmed
    • (Unassigned)

      The Bug

      Duplicates MC-162253. Why you always find your own ticket duplicate after you create one

      Moving from certain chunk to another chunk with certain Render Distance in the certain world will cause massssive FPS lag. I don't know what causes this, but I can provide as much information as I can.

      Here's a table with several sets of Render Distance, source chunk, and destination chunk which cause massive FPS drop. I believe the spawn chunk is (1, 5).

      Render Distance Source Chunk Destination Chunk
      2 (0, 0) (0, 1)
      2 (0, 8) (0, 7)
      2 (1, 8) (1, 7)
      2 (2, 8) (2, 7)
      2 (3, 8) (3, 7)
      2 (-3, 8) (-3, 7)
      2 (-2, 8) (-2, 7)
      3 (-4, 3) (-3, 3)
      3 (-4, 4) (-3, 4)
      4 (-5, 1) (-4, 1)
      4 (-5, 2) (-4, 2)
      5 (-6, 0) (-5, 0)
      6 (-6, -3) (-6, -2)
      7 (-7, -4) (-7, -3)
      7 (-6, -4) (-6, -3)
      8 (-9, -4) (-8, -4)
      8 (-8, -5) (-8, -4)

      To Reproduce

      1. Download the attached World File.7z. Extract it to .minecraft/saves/. (The whole world is too large to upload, so I deleted many regions. The bug is still reproducible with the attached world file.)
      2. Enter the world.
      3. Set your Render Distance to 2.
      4. Move from chunk (0, 0) to chunk (0, 1).
        • Notice massive lag.
        • Notice root.gameRenderer.level.light_updates takes too long in the game log.
      5. Move from chunk (0, 1) back to chunk (0, 0).
        • Notice little lag.
      6. Set your Render Distance to 4.
      7. Move from chunk (0, 0) to chunk (0, 1) again.
        • Notice little lag.
      8. Move from chunk (0, 1) back to chunk (0, 0) again.
        • Notice little lag.

        1. Force Crash Report.txt
          3 kB
          [Mod] SPGoding
        2. Game Log.log
          12 kB
          [Mod] SPGoding
        3. Video.mp4
          9.20 MB
          [Mod] SPGoding
        4. World File.7z
          6.51 MB
          [Mod] SPGoding

            Unassigned Unassigned
            SPGoding [Mod] SPGoding
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              Created:
              Updated:
              Resolved:
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