The South/West Rule has a wide variety of effects throughout the game. What actually causes it?

  • 3
    Questions about why bugs occur are off topic. Questions about how bugs work in-game is on topic. If the explanation of how a bug works happens to include why it occurs, that is just a bonus. See this meta topic: meta.gaming.stackexchange.com/questions/2100/… Commented May 18, 2011 at 14:56

3 Answers 3


The South/West Rule may be related to the fact that traveling south or west causes one's horizontal spatial coordinates to increase; traveling north or east causes X- or Z-coordinates to decrease, respectively.

I therefore assume it is because the coordinates are rounded up to whole integers when it's a ambiguous situation.

  • 2
    Or perhaps blocks are updated one-by-one in increasing coordinates. At any rate, it's an implementation detail.
    – badp
    Commented May 18, 2011 at 9:57

The South-West rule occurs because of the way Minecraft calculates block locations. For some reason (possibly due to rounding), the collision detection of blocks is slightly off. This causes strange effects. You can see the phenomenon clearly by creating an arrangements of blocks like below, and brushing up against each corner. The lava's collision box is slightly offset, so you get damaged.

enter image description here

  • I've noticed that if you replicate and extend the same configuration upwards, but have water in the center instead of lava, you can swim up the SW corner, without entering the water itself.
    – Kurley
    Commented May 24, 2011 at 9:49

If you take a look at this post Do positive coordinate locations give more ore in Minecraft? it acctually explains everything

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