Warning, Big Wall of Text incoming, prepare to be critted.
Digital Mini Worlds
Various mods add world generation, with various levels of customization. All thought suffer from the following issues: They tend to hurt servers, resource cost is minor for what you get back, generation is via some mystical "magic".
DMW allows a player to define a miniature world that's End shaped, and have that world generated in a dimension. What generates in this world all depends on the blocks used to define that world. It will be very resource intensive, and in most cases, you should get back the resources you invested, with some profit.
These worlds have no biomes as such, being randomly assembled from the components supplied.
A created world will have a barrier at it's chunk edges, preventing further travel. Beyond the barrier this area is unclaimed, and at some point another island might be generated there. Any touching claimed areas will result in the barrier being removed, so players can build bridges between islands.
The Process:
Block 1 "Dimension Definer" - Creates a dimension
This blocks sole purpose is to define the basic attributes of the dimension, such as sky colours, timescale, weather, sky effects and most importantly, the size of the dimension in chunks
This block can be limited to allow only OP access, giving servers the option to limit the number of dimensions, without limiting the world creation.
Block 2 "World Designer" - Creates a world
Creating a world requires a "World Foundation" item. With just this item and nothing else, you'll generate a stone End style island of a specific radius. Highly unexciting. But, the rest of the GUI gives you customisation options, which will show you the overall complexity of the world. The higher the complexity, the smaller the radius of the island. Adding more "World Foundations" will increase radius.
Customisation is separated into "Terrain", "Ores", "Flora" and "Features". Almost any block can go into any of these categories, but depending on the category and block, they might add more complexity. For example, a diamond block terrain would be more complex then a diamond block feature.
Each customisation option has 4 inventory slots, each item added adds 1% chance of that block type (or item associated block) being generated (max 64%).
"Terrain" controls what is generated for rock, so for overworld style, this is stone, dirt and gravel
"Ore" controls the ores found within the terrain. Generation is either Terrain or Ore, depending on the ratio of blocks between the two
"Flora" controls what plants can be found, saplings are just planted when the world is generated. Being a new world, you need to wait for them to grow.
"Features" controls extra fancy features, such as glowstone formations, lakes and many other things - time to experiment!
There's also an extra customisation that allows to you add more void chunks around your island, if you need the space.
Once you hit the "Create" button, you'll be given a "chip" that has all the details of the world. All the resources are consumed.
Block 3 "Cartographer" - Places the world, and lets you travel to them
This block shows a mini-map of the dimension, showing used and available chunks. With a new world, insert it into this block (where it is consumed), and choose where to generate the island. The Cartographer will also generate a "chip" that you can put into a "portal" to travel to these islands.
That's the basic idea, unfortunately I haven't the faintest idea about Java, otherwise I'd attempt to make the mod myself
Nice thing about this mod is that you can design almost anything you like for your island, if you have the resources, so early game, fairly "normal" style worlds for mining, later on, bling islands for your latest palace/fortress.
