edit: I've done some investigation and digging and I found my answer. I'll let this thread die since it's actually easier to search for info on the topic than I had realized. But I will also share my best links in case someone else searching for the same answer stumbles across this.
Milesluigi has a detailed video showing how to spawnproof a rail system in the nether. It's old but should work in pretty much any version of Minecraft.
This post on reddit says mobs no longer spawn on carpets, so there may be other blocks that can be used, such as snow layering. Also the new grass path blocks give a way to spawnproof and they should always work the same as half slabs even if the change is reverted and carpets stop working, because they are the same kind of block as half slabs--transparent with a shortened hitbox.
Here's a video demonstrating half-slab spawn-proofing.
Originally, mobs could not spawn on top of upper slabs, but now they can. They still cannot spawn on top of lower slabs.
I have been told and also read that mobs can't spawn on half-slabs, but it seems like they are spawning on them in my game. I've got a minecart rail system that is enclosed, and it keeps getting zombie pigmen spawning in it. Can anyone tell me how/why/where they are spawning?
They can't spawn on bottom half slabs, they still spawn on top half slabs or double slabs as far as I know.
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Want some advice on how to thrive in the Suggestions section? Check this handy list of guidelines and tips for posting your ideas and responding to the ideas of others!
A mob can only spawn in a certain position if the block below the spawn block has a solid top surface. Blocks with a slab in the top half of the block-space have a solid top surface. Blocks which only have a slab in the bottom half, do not.
Mobs spawning on upper half-slabs is nothing new; I'm not sure why the second video is claiming that mobs can now spawn on top of half-slabs as of 1.7 when they could in older versions, likely far older than 1.6.4:
Likewise, this is also true for stairs, hoppers (claimed here to be a 1.9+ mechanic, but this proves otherwise), and 8-high snow layers (1-high snow layers also allow mobs to spawn but due to the fact that prior to 1.8 the pack center had to be an air block it inhibits pack spawning, entirely in Superflat with a decreased spawn rate in normal worlds):
/**
* Performs check to see if the block is a normal, solid block, or if the metadata of the block indicates
* that its facing puts its solid side upwards. (inverted stairs, for example)
*/
public boolean isBlockTopFacingSurfaceSolid(Block par1Block, int par2)
{
return par1Block == null ? false : (par1Block.blockMaterial.isOpaque() && par1Block.renderAsNormalBlock() ? true : (par1Block instanceof BlockStairs ? (par2 & 4) == 4 : (par1Block instanceof BlockHalfSlab ? (par2 & 8) == 8 : (par1Block instanceof BlockHopper ? true : (par1Block instanceof BlockSnow ? (par2 & 7) == 7 : false)))));
}
edit: I've done some investigation and digging and I found my answer. I'll let this thread die since it's actually easier to search for info on the topic than I had realized. But I will also share my best links in case someone else searching for the same answer stumbles across this.
Milesluigi has a detailed video showing how to spawnproof a rail system in the nether. It's old but should work in pretty much any version of Minecraft.
https://www.reddit.com/r/Minecraft/comments/49h033/do_hostile_mobs_spawn_on_rails_in_19/
This post on reddit says mobs no longer spawn on carpets, so there may be other blocks that can be used, such as snow layering. Also the new grass path blocks give a way to spawnproof and they should always work the same as half slabs even if the change is reverted and carpets stop working, because they are the same kind of block as half slabs--transparent with a shortened hitbox.
Here's a video demonstrating half-slab spawn-proofing.
Originally, mobs could not spawn on top of upper slabs, but now they can. They still cannot spawn on top of lower slabs.
- - - - - - - - - - original message - - - - - - - - - -
I have been told and also read that mobs can't spawn on half-slabs, but it seems like they are spawning on them in my game. I've got a minecart rail system that is enclosed, and it keeps getting zombie pigmen spawning in it. Can anyone tell me how/why/where they are spawning?
Here's the structure of the rail system:
I want
ocean content(thanks Möjang!),nether biomes(again thanks!!), and savanna passive mobs (meerkats incoming!?).They can't spawn on bottom half slabs, they still spawn on top half slabs or double slabs as far as I know.
Want some advice on how to thrive in the Suggestions section? Check this handy list of guidelines and tips for posting your ideas and responding to the ideas of others!
http://www.minecraftforum.net/forums/minecraft-discussion/suggestions/2775557-guidelines-for-the-suggestions-forum
A mob can only spawn in a certain position if the block below the spawn block has a solid top surface. Blocks with a slab in the top half of the block-space have a solid top surface. Blocks which only have a slab in the bottom half, do not.
Village Mechanics: A not-so-brief guide - Update 2017! Now with 1.8 breeding mechanics! Long-overdue trading info, coming soon!
You think magic isn't real? Consider this: for every person, there is a sentence -- a series of words -- which has the power to destroy them.
Mobs spawning on upper half-slabs is nothing new; I'm not sure why the second video is claiming that mobs can now spawn on top of half-slabs as of 1.7 when they could in older versions, likely far older than 1.6.4:
Likewise, this is also true for stairs, hoppers (claimed here to be a 1.9+ mechanic, but this proves otherwise), and 8-high snow layers (1-high snow layers also allow mobs to spawn but due to the fact that prior to 1.8 the pack center had to be an air block it inhibits pack spawning, entirely in Superflat with a decreased spawn rate in normal worlds):
TheMasterCaver's First World - possibly the most caved-out world in Minecraft history - includes world download.
TheMasterCaver's World - my own version of Minecraft largely based on my views of how the game should have evolved since 1.6.4.
Why do I still play in 1.6.4?