Raids Can Spawn On Any Block, Anywhere

Nope, not fixed. I just tested and got them to spawn on leaves, giant mushrooms, and stone with buttons on top.

Why aren’t the illagers taking damage form the magma

@unknown I don't know, but that's not part of this bug report. Feel free to create a new report if you have that problem and can't find an earlier ticket reporting it.

@unknown They don’t take damage because there was another bug, that caused mobs to not take damage from magma blocks, which has already been fixed. See MCPE-47518

Affects 1.16.40 Hotfix.
Affects 1.16.100.55 Beta.

Affects 1.16.100.56 Beta.

Affects 1.16.100.57 Beta.

Affects 1.16.100.58 Beta.

@GinePik: Please do not add a new comment for every affected version. That makes the substantive comments harder to find. You can just edit your last comment to change the version. Also, it is not very important to add every new beta version to a bug that exists in the current release version. The most recent release version is enough to show that it is still an active bug, unless there is some question about whether a reported beta fix is effective.

They now spawn on scaffolding once in a while... I've watched them spawn right next to me on top of scaffolding in my bedrock realm many times now. 

I tested this and they cannot spawn on leaf blocks. Raids have always been able to spawn on any block except leaf blocks so this is completely normal behaviour for pillager spawning.

Tested in the beta 1.16.220.52, raids don't spawn on azalea leaf and flowering azalea leaf blocks.

Tested in 1.17.2, several blocks are now spawn proof from raids, the list contains:

Amethyst Bud (large), Twisting vines, Lantern, Powder snow, trapdoors, coral (and fans), Big dripleaf, campfire, fences, doors, conduit, anvils, composters, cauldron, sea pickle, grindstone, brewing stand, glow lichen, slime block, iron bars, signs, bells, redstone dust, lectern, shulker boxes, lightning rods, stone buttons (wooden buttons won't work), end portal (frames), armor stand, boats, minecarts, rails and chains.

Magma and fire still won't prevent raid spawns which is a bummer, but now leaves are no longer alone to prevent raid spawns. Further testing is needed though.

Jesse Kohn: I had a friend thoroughly test raid spawns and they found that nothing has changed: raids can spawn on any block except (1) blocks without collision, (2) leaves, (3) scaffolding. They also won't spawn inside of 2-deep water. The test involved covering solid blocks with various blocks and starting raids, then covering leaves with various blocks and starting raids.

Please provide more details on your testing if you still think there is a change.

I've only tested this on a 3x3 area in the end void, not in a bigger scale. I apologize for the previous comment posted.

I suspect one of the factors complicating testing this issue is that we keep talking about "spawning a raid" without defining what that phrase means. In the first place, raids don't spawn, it's raid waves that spawn, but that's a trivial correction. More substantively, spawning a raid wave means spawning a more or less fixed combination of illagers, vindicators, witches, evokers, and ravager beasts all at the same time. Such a complex spawn is very different from spawning an individual mob herd (a.k.a. "pack spawn"), but that's the mechanic we're relying on as we try to understand how it works. I think that's where we're going wrong, because raid spawning can't possibly work the same way as herd spawning.

Here's why: When the game is spawning a mob herd, all the mobs spawn on a single block and then spread out, so the game only has to find one block eligible for spawning one kind of mob. If the first few blocks it looks at don't pass the test, it's no big deal, it can retry lots of times before any delay is apparent. But when the game is spawning a bunch of mobs all at once, there are many more chances for a block eligibility test to fail. This magnifies the possibility of failure by a factor equal to the number of mobs, and if a block test failure causes the whole raid wave spawn attempt to fail (which is what happens in herd spawning), the failure possibility for the wave as a whole goes up exponentially. It could easily take half an hour or more for a wave to spawn successfully.

So to understand what our testing results mean in a way that can make all of our findings consistent with each other, we first need a new model of how raid wave spawning mechanics work. I'm now going to propose one possible model that can explain not only some of our inconsistent observations, but also might explain why they spawn in ridiculous places like on lava and in fire. I'm mostly just guessing and other models are possible, so keep an open mind.

I propose that the game spawns a raid by choosing a block to serve as what I'll call an anchor point. The anchor point will define the center of a sphere within which all the wave's mobs will spawn. (Coincidentally, it will also be the point that the raid horn emanates from.) The anchor point might have conditions that are tested for wave spawn eligibility, like a normal mob, while the individual mob herd spawns are scattered to random blocks within the sphere and have less rigorous conditions, or none at all, so that there's less likelihood of them failing to qualify and cancelling the entire spawn attempt. The spawn block conditions associated with the anchor point would be sufficient to avoid spawning the entire raid in a large-scale feature such as an ocean, lava lake, fire pit, etc., while the subsequent spawning of mob herds would be subjected to few or no spawn block conditions—which is why they appear to spawn on almost anything, and also why they often spawn underground.

(Side note: The program's data folder contains a folder called "spawn_groups" which contains a file for each wave, giving its mob composition and the conditions for spawning each type of mob. I notice that all the mobs have the spawns_on_surface component, which should mean they can only spawn on a block that has sky access. Since we know that raid mobs spawn underground sometimes, I think it's probable that these files are a work in progress and aren't actually used by the game yet, that the game instead has the spawning logic for raids hard-coded. It would make sense, then, that the spawn_groups files are meant to be the solution to the underground spawning problem MCPE-45183, and probably for this problem as well, but there is still some work to be done. Interestingly, the spawn_groups files do not specify any spawn block conditions other than on-surface spawning and a max distance of 1024 from (presumably) the anchor point.)

The point of all this discussion is that in trying to track which blocks raid mobs spawn on, we might be trying to infer the details of game mechanics that don't exist in the first place. Furthermore, there's some pretty good evidence that Mojang is in the process of converting raid spawning to a data-driven mechanic and that they already know how they're going to solve it, so additional information isn't really needed at this point.