gaemstone/src/gaemstone.Bloxel/Systems/BasicWorldGenerator.cs

using System;
using gaemstone.ECS;
using gaemstone.Utility;
using static gaemstone.Bloxel.Components.CoreComponents;
using static gaemstone.Bloxel.Constants;

namespace gaemstone.Bloxel.Systems;

[Module]
[DependsOn<gaemstone.Bloxel.Components.CoreComponents>]
public class BasicWorldGenerator
{
	private readonly FastNoiseLite _noise;
	private readonly Random _rnd = new();

	public BasicWorldGenerator()
	{
		_noise = new(new Random().Next());
		_noise.SetNoiseType(FastNoiseLite.NoiseType.OpenSimplex2);
		_noise.SetFractalType(FastNoiseLite.FractalType.Ridged);
		_noise.SetFractalOctaves(4);
		_noise.SetFractalGain(0.6f);
	}

	[Symbol, Tag]
	public struct HasBasicWorldGeneration {  }

	[System]
	public void Populate(World world, EntityRef entity,
		in Chunk chunk, ChunkStoreBlocks blocks,
		[Not] HasBasicWorldGeneration _)
	{
		var stone = world.LookupByPathOrThrow("Stone");
		var dirt  = world.LookupByPathOrThrow("Dirt");
		var grass = world.LookupByPathOrThrow("Grass");
		for (var localX = 0; localX < ChunkLength; localX++)
			for (var localY = 0; localY < ChunkLength; localY++)
				for (var localZ = 0; localZ < ChunkLength; localZ++) {
					var globalX = chunk.Position.X << ChunkBitShift | localX;
					var globalY = chunk.Position.Y << ChunkBitShift | localY;
					var globalZ = chunk.Position.Z << ChunkBitShift | localZ;
					var bias = Math.Clamp((globalY / 32.0f + 1.0f), 0.0f, 1.0f);
					if (_noise.GetNoise(globalX, globalY, globalZ) > bias)
						blocks[localX, localY, localZ] = _rnd.Pick(stone, dirt, grass);
				}
		entity.Add<HasBasicWorldGeneration>();
	}
}