I created a world in 14w03b, and it's a great world, it has 3 villages all in a row, the middle one having 2 monster dungeons under it, a zombie and a spider.
With the new snapshot today, 14w04a, I re-created the world to see the new villagers. I started digging my hole back down to the 2 monster dungeons, only to find that they aren't there... and no other ones are on the map...
Here are 2 shots from Minutor of the two worlds...
The first world created in 14w03b:
Note the mossy stone? those are the dungeons in question.
Here is the same exact place, but created in 14w04a:
Note that everything else is the same...
Edit...
They won't let me use Puush here anymore for some odd reason... here are the 2 pics on my imgur page, Towns was the first one, and townies was the second. http://imgur.com/a/uHrEc
Uh. I heard that the locations of dungeons aren't tied to the seed, so if you were to remake the same world in the same version two times using the same seed, the dungeon locations would be different each time. I'm guessing this is what happened.
That is not true, Pikaguy. Dungeons do actually have there fixed places, just like the other structures (however, they are not "real" structures, because you will find them also in a world without structures). Even if you recreate your world as amplified world, you will find the dungeons on the same spots.
From my experience the only thing that changes the location is changing how caves, ravines, etc generate (as I've noticed when using Unmined to check cave generation when I mod it), as dungeons generate wherever a suitable spot is found, always connected to some sort of cave, but not in the middle of a large cave (possibly appearing to be isolated if the cave is small enough, they even generate connected to underground water/lava lakes). However, the locations they appear in are still fixed; the code randomly attempts to place 8 dungeons in each chunk between y=0-127 (actual number far less).
Anything that spawns in a seed should spawn every time that seed is created. you have seen all those seed spotlight videos... Those two dungeons should have spawned. and there were no other dungeons on the map. period.
While testing, I came across another bug; a mineshaft dirt room that has no associated mineshafts:
(seed is -123775873255737467, default)
I didn't find any dungeons either, in an area a thousand blocks on a side; MCEdit also found no moss stone and only four monster spawners, cave spider spawners in abandoned mineshafts.
I decompiled the jar and as far as I can tell, dungeons SHOULD generate, at least from looking at ChunkProviderGenerate; here is a comparison of the deobfuscated code from 1.6.4 and the 14w04a code, which includes the generators for lakes for comparison:
1.6.4 code, ChunkProviderGenerate, under populate():
Now, they did change some stuff, allowing for the increase in terrain to the world height limit (previously limited to 128 before 1.7), which means that dungeons are now rarer, as it still makes 8 attempts over the range but now over 256 blocks instead of 128. Combined with a decrease in cave frequency, which already made them rarer in 1.7, this means that dungeons are even rarer still; however, there should still be several in a larger area like I tested.
For comparison, my first main world made in 1.5.1-1.6.2 contains 2,786 moss stone in a similarly sized area; if the average dungeon size is 7x9 overall (5x7 interior) with 75% of the bottom being moss stone, then each one has on average 47 moss stone, so 2,786 moss stone is about 59 dungeons (since I explored most of the caves in the area and destroy most spawners I find there were only 16 monster spawners).
Note also that by changing the range from 128 to 256 the locations of dungeons will change accordingly, moving up to twice the original y-coordinate - if the new location is suitable, that is. Now, I didn't check to see if they had already changed this in 1.7 but I imagine that they did, as they did with lakes and other stuff.
With the new snapshot today, 14w04a, I re-created the world to see the new villagers. I started digging my hole back down to the 2 monster dungeons, only to find that they aren't there... and no other ones are on the map...
Here are 2 shots from Minutor of the two worlds...
The first world created in 14w03b:
Note the mossy stone? those are the dungeons in question.
Here is the same exact place, but created in 14w04a:
Note that everything else is the same...
Edit...
They won't let me use Puush here anymore for some odd reason... here are the 2 pics on my imgur page, Towns was the first one, and townies was the second.
http://imgur.com/a/uHrEc
From my experience the only thing that changes the location is changing how caves, ravines, etc generate (as I've noticed when using Unmined to check cave generation when I mod it), as dungeons generate wherever a suitable spot is found, always connected to some sort of cave, but not in the middle of a large cave (possibly appearing to be isolated if the cave is small enough, they even generate connected to underground water/lava lakes). However, the locations they appear in are still fixed; the code randomly attempts to place 8 dungeons in each chunk between y=0-127 (actual number far less).
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?
(seed is -123775873255737467, default)
I didn't find any dungeons either, in an area a thousand blocks on a side; MCEdit also found no moss stone and only four monster spawners, cave spider spawners in abandoned mineshafts.
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?
14w04a code, asc.class, decompiled with Java Decompiler:
Now, they did change some stuff, allowing for the increase in terrain to the world height limit (previously limited to 128 before 1.7), which means that dungeons are now rarer, as it still makes 8 attempts over the range but now over 256 blocks instead of 128. Combined with a decrease in cave frequency, which already made them rarer in 1.7, this means that dungeons are even rarer still; however, there should still be several in a larger area like I tested.
For comparison, my first main world made in 1.5.1-1.6.2 contains 2,786 moss stone in a similarly sized area; if the average dungeon size is 7x9 overall (5x7 interior) with 75% of the bottom being moss stone, then each one has on average 47 moss stone, so 2,786 moss stone is about 59 dungeons (since I explored most of the caves in the area and destroy most spawners I find there were only 16 monster spawners).
Note also that by changing the range from 128 to 256 the locations of dungeons will change accordingly, moving up to twice the original y-coordinate - if the new location is suitable, that is. Now, I didn't check to see if they had already changed this in 1.7 but I imagine that they did, as they did with lakes and other stuff.
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?
https://bugs.mojang.com/browse/MC-45628