At the moment I can only figure out how to add one biome to my custom world type via: 

 

public class worldMediterranean extends WorldType {
  
	public worldMediterranean() {
		super("Respublica");
			
	}
	
	@Override
	public BiomeProvider getBiomeProvider(World world){
		
		
		return new BiomeProviderSingle(modBiomes.LATIUM);
		
	}	
}

 

However I cannot figure out how to make the custom world type have several biomes that are only my custom biomes. Ive looked into the GenLayer and GenLayerBiome but those classes are so confusing as to what they are exactly doing. Ive looked around the githubs of choonster, the biomeoplenty github and other to try and grasp how to do it but ive come up short. If anyone could give a straightforward method it would be appreciated.

You're confusing the biome with the biome provider. A BiomeProvider has a getBiome() method which returns the biome for a given BlockPos. However, you've used a BiomeProviderSingle which always returns the same biome. So instead you should use a general BiomeProvider and @Override the the getBiome() method to provide the biomes that you want. 

 

In other words, the WorldType provides the BiomeProvider which provides the Biome instances.

When looking at BiomeProvider.getBiome it appears to be a single return value from 'Biome' so how would that be used for multiple biomes?

2 hours ago, daruskiy said:

When looking at BiomeProvider.getBiome it appears to be a single return value from 'Biome' so how would that be used for multiple biomes?

Right, it only returns one biome but it returns it based on the BlockPos you pass to the method. So you return different biomes based on the position.