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 partial class BasicWorldGenerator
{
	// TODO: Turn these into a component on the module.
	private static readonly FastNoiseLite _noise;
	private static readonly Random _rnd = new();

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

	[Tag]
	public struct BasicWorldGenerationDone {  }

	[System]
	public static void Populate<T>(
		World<T> world, Entity<T> entity,
		in Chunk chunk, ChunkStoreBlocks blocks,
		Not<BasicWorldGenerationDone> _)
	{
		var stone = world.LookupPathOrThrow("Stone");
		var dirt  = world.LookupPathOrThrow("Dirt");
		var grass = world.LookupPathOrThrow("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<BasicWorldGenerationDone>();
	}
}