I've written a mod targeted specifically at modders writing world-gen code. I wrote it because I was looking for an X-Ray mod to test out my world gen I was writing for Steam and Steel but I couldn't get any working in my development enviroment.
This mod was not designed to be used in a production setting. It has not been tested or verified stable in these environments. It was written specifically for mod developers, not server admins.
It provides four commands to help you debug your ore generation.
/chunkxray [radiusInChunks] [filter]
This command will destructively remove a set of blocks in a square chunk radius from your world, allowing you to see the ore underneath.
The blocks removed are:
In order to prevent massive world lag, it will not remove any block that is touching Lava or Water.
You can specify a filter to limit the blocks being removed. It uses a partial match, but is case sensitive, so typing 'stone' will not match 'sandStone'
Although there is no limit, attempting to remove too many chunks worth of blocks will result in the server and then the client stalling while it processes your command.
This command will cause the chunk to be regenerated. Depending on the implementations of the generation you may not end up with a 100% identical chunk. This is especially true around the edges as the order that the chunks are created can have an impact on ore generation.
/chunksurvey [radiusInChunks] [filter]
This command will scan all of the blocks in a chunk and give you a report on the various blocks found in a chunk.
You can specify a filter to limit the blocks being surveyed.
Allows you to replace one type of block with another.
I do not recommend or condone running this in any environment that you care about. You theoretically need to be op on the server to run it, but I have to admit I have not tested it. If someone destroys your world because you installed this on a server, I take no responsibility for it.
The mod is currently compatible with Minecraft 1.7.10.