Minecraft brightness / lightmap calculator

I recently wanted to light up a semi manual farm in my Minecraft world in a specific way with the least amount of light sources possible but I couldn’t find any helper tools.

So I build a LibreOffice Calc document with two sheets. One for height levels of the floor blocks (or the air blocks above the floor) and the other one filled with a light level calculating formula and this is the result:

CC BY-NC-SA 4.0 (WP.com doesn’t allow ODS files so I had to convert to XLSX :-/)

How to use it:

  • Open sheet “LL” and enter one set of corner coordinates of your in-game target area in the upper left corner in the dark-green (E3) and dark-blue (C5) cells.
  • Switch the x/z dimension axes between ascending and descending by entering -1 or 1 in A2 and A3.
  • Set the required minimal light level in A1. The formula stops below that level and just assumes a brightness of 0. Additionally the conditional formatting uses this value for the green background.
  • Switch to sheet “HM” and fill in the (relative) heights of your floor level (or just fill it with zeros if the floor is flat).
  • Switch back to sheet “LL” and enter your floor light levels wherever you want to place a light source. Note that you can’t enter the height of light sources so you need to calculate the corresponding floor light level manually (eg. torch two blocks above the floor -> 14-2=12).
  • Press Ctrl+Shift+F9 to force recalculation until all cells are stable. -> Voilà, your lightmap is ready.

Caveats:

  • The formula assumes all light sources are always above the surrounding ground. -> When you place a light source on the ground and the ground somewhere around it is higher the light level isn’t decreased by one but increased instead.

Disclaimer:

Use at your own risk. I take no responsibility for any material or immaterial damages or anything else resulting from anyone downloading, opening or using the provided document.

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