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I am currently about a week behind posting videos to YouTube. So you won’t see my video about this week’s Minecraft 1.9 snapshot 15w38a until next week or the week after.

The Four Horsemen Of The Apocalypse have arrived!  Which is pretty cool (and scary as heck) but the big bugfix news is that mobs won’t glitch through fences and blocks any more. This is huge – livestock shouldn’t be able to escape from their fenced-in pens any longer. Or suffocate in the sides of pits.

But the bug that caused items to glitch through blocks is also the bug that the very common (and useful) item elevator created by test137E29 relies on.

My feeling towards mechanics that rely on bugs (even very old bugs) is that they are risky and can break with any given release. So I’m OK with the item elevators in the Guardian and Witch farms on the Minecraft LAN Party! server breaking when we update to the 1.9 release. I can always put in a dropper elevator, as annoying as they are.

But the bigger issue is that items (such as drops from mined blocks) stopped being displaced up when a block was placed in the space where the item was. Instead of rising to the new surface, the item gets trapped in the block. This didn’t make sense to me – an item and block shouldn’t be able to occupy the same place at the same time (physics still apply to the world of Minecraft, right?).

But more importantly, it makes mining really tricky – if you dig out a vein of ores from the floor, you have to jump down in the hole to pick up the ores before filling in the hole, or the ore items will be stuck in the floor.

Turns out this is related to the item/block hit box bug. Grum added a comment to this very old bug in the Mojang bug tracker yesterday:

Things will not get pushed up when they get stuck in a block. They will prefer to fall down.

I think the current behaviour is at least predictable

Which is all fine and good, but if there is no possibility to move down, the item should move up. Placing blocks should be a different circumstance than an item moving into a block (which was the real bug).

There were a few people on the bug tracker and on the subreddit complaining about what this meant for item elevators, but mostly everyone was focused on the skeleton horsemen. And no one seemed to notice the whole items not displacing upwards thing.

Well, fortunately panda4994 did the right thing by filing a bug report with Mojang. Unfortunately, the bug got closed as “intended behavior” per Grum’s aforementioned rationale.

The problem with complaining is, when you go all hysterical over something like borked item elevators (which were based a bug in the first place) it’s really easy for anyone in a position to do anything about it to ignore you. It’s best to take a deep breath, consider “Why did they do this?” and figure out a rational explanation for why breaking your item elevator (which was based on a bug in the first place) is a bad thing. They are trying to make the game better, not make you angry.

My first job out of college was testing video games. My brain functions well for that kind of work. It’s mostly pattern recognition – you have to be able to distinguish between features and bugs because the design document is never complete enough to tell you for sure. And telling the developer that you found a bug is essentially accusing them of making a mistake. So if it’s not a major crash, they have an emotional incentive to discount the bug report. In my experience, the best way to get the developers to accept a bug report is to explain how the behavior is inconsistent. Programmers hate inconsistency.

So, despite the bug being closed, I added a comment to the ticket:

I understand items preferring to fall down, but if there is no way for them to go down, placed blocks will not displace them at all. Meaning the items share the same space as a placed block. This does not make sense from a physics standpoint. As long as I can remember, placed blocks have always displaced floating items.

This intended functionality feels more like a bug, and it makes mining and building in game much more difficult.

And look at what happened! Three minutes later, Grum responded:

Mmm placed blocks should displace them.

I’ll look into it.

YAY!

Okay, okay, this was indeed an unintended consequence of the item/block hit box bugfix. Someone would have pointed it out, and they would have fixed it. But I have to say I was pretty pleased with myself.

Today snapshot 15w38b was released, and items now get displaced by placed blocks. The glass item elevators still don’t work, and I would not expect that to change. But that’s OK – keeping mobs in their pens is more important. I can always build dropper elevators.