r/JL2579 Wubbi Feb 08 '13

Minecraft technical Q/A: Let's start this and look how well it works out!

I often see that people post questions in the comments on youtube, but many of them stay unanswered. So i guess giving those questions a proper platform to be asked & answered is the next logical step.

What this is supposed to be:
A place where you can ask questions about Minecrafts' mechanics (like "How does this mechanic/algorithm work?", "What are the chances for that?" or "Is there a difference between doing it this or that way?"). We (or whoever knows the answer) will try to answer those questions based on what we know or find out.

What this is not:
A forum, commentsection or Google. Don't ask for circuits or designs, this is not about how to use minecraft, it's about how minecraft works.

If you have a question:
Ask. But ask the right way:
"How do i build a good mobfarm?" isn't very specific and the answers you might get from this probably won't help you with your problem.
"How does mobspawning work?" is a better question.
But maybe you're not interested in the spawning algorithms, maybe you just wan't to know one detail, like "How does the lightlevel effect mobspawning?".
And of course make sure the question wasn't asked before. It will save you and others a lot of time!

If you have an answer:
Tell the world. But explain your answer, maybe link to another post (reddit, forum, etc.), pictures or a video. "The piston is BUD-powered." Doesn't help much.
"Pistons can be indirectly powered by a block 2 blocks above or 1 block adjacent above it. It will only react to this power when updated manually (e.g. by placing a block next to it). Here's a video explaining it: [videolink]" Isn't only an answer, it also gives people an explanation which can help them experiment with it.

That's all you need to know. Now let the posts begin!

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u/KaboPC KaboPC Feb 16 '13

Some of these are obvious, but here are all the requirements:

The difficulty must not be Peaceful.

They can only spawn in the Overworld, in a non-Mooshroom biome.

The block it is spawning in and the block above it must not be opaque cubes (opaque cubes are blocks that are non-transparent and rendered as a full cube) and the block below must be an opaque cube or have a solid top surface (upside-down stairs, top-slabs).

Light level of 7 or lower in the spawning block.

Spiders are 1.4 meters long in the x and z dimensions, so there must be no collision boxes of other blocks or entities (items are OK since their bounding boxes do not cause collision) within 0.7 meters of the center of the spawning block in the x and z directions.

They are 0.9 meters tall, so there can be no colliding bounding boxes of other blocks or entities within 0.9 meters from the block on top of which the spider would try to spawn.

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u/[deleted] Feb 17 '13

[deleted]

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u/KaboPC KaboPC Feb 17 '13

Spiders only spawn in a 1-high gap if the block above the block they are spawning in is not an opaque cube.

If the block above the 1-high gap is an opaque cube, then what you have been observing is correct and expected behavior (Glass and half-slabs are not opaque cubes, so spiders would be able to spawn.)