modify world generator

How can you modify the pocketmine or mcpe world generator. What tool should you use? By mod I meant co plete modification in world generating such as generating buildings.

Change generator-settings in server.properties if the level is generated by server.
If the level is already generated, use an NBT editor like NBTExplorer.

If you want to generate fully customized worlds, you need to write a plugin with a custom world generator script

I want to change the generator itself. Is there anyway to build something manually, compile it into the generator, and run a modified generator? Like used what you build to generate in d8fferent algorithm. Like vaast.org

I meant like a complete custom generator like vaast.org

If you want to customize PocketMine world generator you should run it from source and then recompile the modified PocketMine phar with DevTools

I think vaast.org worlds are made by hand. They don't use a custom world generators but they are a team which builds custom worlds (not world generators)

You don't need to run pocketmine from source if you want a custom generator. There are plugins for that. Suggest you get one of those and modify at will.

He said that he wants to customize the "internal" PM generator. I've already said that he needs to make a plugin

Register a new generator to PocketMine, change the generator type for the world at level.DAT and load the server.

I need a completely empty world with one block at spawn, is this possible?

Please don't thread hijack. Use world painter