Minecraft Wiki talk:Issues/Weekly 12w19a

Pistons with rails
I've noticed pistons that move a block with a rail on it will drop the rail as an item if moved in any direction except when it is pushed up. I think moving a block without dropping the rail as an item could be useful. I understand that it's similar to moving a block with torches on it (and I'm not saying change that too), but I think it could be useful to someone who wants to implement it somehow.

World names reset
Also, I think world names have been reset to their original names. For example, I had a world named "Flat" that I renamed to "Flat2" before I updated to this snapshot; it now says "Flat" again. No big deal, though.

Aquatic mobs
undefined Passive mobs are ridiculously aquatic. I bred a moderate number of cows, sheep, pigs and chickens (30-40 or so) and left them to their own devices on a smallish island. (About 50x40 blocks in size, just inside an ocean biome). After a time I found that at any time around 90% of the mobs would be swimming about in the sea and only 10% of them would be wandering on land. The other way around would be fine... 82.69.54.207 22:42, 10 May 2012 (UTC)
 * I am almost positive this is just the mobs randomly moving around. Because you only had a small bit of land and a lot of water, they simply formed a uniform distribution from the point where you kept them. Vote to remove. --Mattrition 08:37, 11 May 2012 (UTC)
 * Heh, what a touching faith in the infallibility of random movement. :-) Thing is, I didn't wade out to sea before breeding these guys, so if you're right they should mostly stay clustered about on the areas of grass where I originally bred them. OK, let's allow them 90% on land, 10% in water. But mob movement is independent, so the numbers shouldn't matter, and in practice if I'd only had a dozen mobs, I'd expect all of them to end up in the water quite quickly. Once there, they tend to stay there because "Mobs will stop wandering within 5 seconds if there is no player within a 32 block radius. In this state, they will glance around randomly, but they won't walk anywhere. They can still be moved by other means such as flowing water, minecarts, etc.".
 * Basically, there is a hidden bias in the mob movement algorithm. 'If {mobs} are completely surrounded by grass, they will wander aimlessly', fine. 'If they can't see any grass, they will wander toward light.' That bit means a mob who falls underground will try to get back to the surface where it's light. But if it's equally light everywhere - as it is in lit caves, and on the surface - the mobs once again revert to just wandering randomly, because 'towards light' doesn't provide any guidance. The effect is that if they ever wander randomly too far away from grass, they can't find their way back, and then they freeze in place. Result: Mobs constantly tend to drift away from suitable terrain, i.e. grass, and towards unsuitable terrain such as water, desert, lit caves etc.
 * A refinement to the movement algorithm which would probably fix the behaviour is something like this: 'If {mobs} are completely surrounded by grass, they will wander aimlessly'. 'If they can't see any grass, and light levels are below {some mid-level threshold} they will wander toward light.' 'If they can't see any grass, and light levels are above {some mid-level threshold}, they will try to move uphill or towards shallower water.'82.69.54.207 11:45, 11 May 2012 (UTC)
 * OK, so it sounds like you've looked into this more than the "average" submitter does when they submit this kind of thing. Sure, that sounds like there is a flaw in mob behaviour. But its not actually a bug. I would consider it as an annoyance. If enough people agree that it is an issue with the game, we can make it a major annoyance. --Mattrition 12:10, 11 May 2012 (UTC)