minecraft-kajetans-mod/src/main/java/me/km/world/ModWorldGeneration.java

package me.km.world;

import java.util.function.Supplier;
import me.km.blocks.ModBlocks;
import net.minecraft.block.Block;
import net.minecraft.block.Blocks;
import net.minecraft.world.biome.Biome;
import net.minecraft.world.gen.GenerationStage;
import net.minecraft.world.gen.feature.ConfiguredFeature;
import net.minecraft.world.gen.feature.Feature;
import net.minecraft.world.gen.feature.OreFeatureConfig;
import net.minecraftforge.registries.ForgeRegistries;

public class ModWorldGeneration {
    public static void register() {
        // search for all biomes which generate ore
        for(Biome biome : ForgeRegistries.BIOMES.getValues()) {
            biome.getGenerationSettings().getFeatures().forEach(list -> {
                for(Supplier<ConfiguredFeature<?, ?>> entry : list) {
                    if(entry.get().config instanceof OreFeatureConfig) {
                        OreFeatureConfig ore = (OreFeatureConfig) entry.get().config;
                        if(ore.state == Blocks.IRON_ORE.getDefaultState()) {
                            addFeatures(biome);
                            break;
                        }
                    }
                }
            });
        }
    }

    private static void addOre(Biome b, Block ore, int maxCount, int spawnTries, int maxHeight) {
        b.getGenerationSettings().getFeatures().get(GenerationStage.Decoration.UNDERGROUND_ORES.ordinal()).add(() -> {
            return Feature.ORE.withConfiguration(
                    new OreFeatureConfig(OreFeatureConfig.FillerBlockType.BASE_STONE_OVERWORLD,
                            ore.getDefaultState(), maxCount)).range(maxHeight).square().func_242731_b(spawnTries);
        });
    }

    private static void addFeatures(Biome biome) {
        //          | max   | bottom | top    | max  | spawn |
        // name     | size  | offset | offset | high | tries |
        // ---------------------------------------------------
        // coal     |    17 |      0 |      0 |  128 |    20 |
        // iron     |     9 |      0 |      0 |   64 |    20 |
        // gold     |     9 |      0 |      0 |   32 |     2 |
        // redstone |     8 |      0 |      0 |   16 |     8 |
        // diamond  |     8 |      0 |      0 |   16 |     1 |
        // lapis    |     7 |      - |      - |    - |     - |
        // copper   |     9 |      0 |      0 |  128 |    25 |
        // tin      |     6 |      0 |      0 |   96 |    12 |
        // silver   |     9 |      0 |      0 |   64 |     3 |

        addOre(biome, ModBlocks.copperOre, 9, 25, 128);
        addOre(biome, ModBlocks.tinOre, 6, 12, 96);
        addOre(biome, ModBlocks.silverOre, 9, 3, 64);
    }
}