riversong-code-showcase/Source/Riversong/Game/World/Terrain/GrassLodGameSystem.cs

namespace DanieleMarotta.RiversongCodeShowcase
{
    public class GrassLodGameSystem : GameSystem, IUpdatable
    {
        [InjectService]
        private GameConfig _config;

        [InjectService]
        private IScene _scene;

        [InjectService]
        private WorldRenderingState _renderingState;

        public GrassLodGameSystem(IServiceLocator serviceLocator) : base(serviceLocator)
        {
        }

        public void Update()
        {
            var grassConfig = _config.Terrain.GrassLODs;
            var cropsConfig = _config.Terrain.CropsLODs;

            foreach (var chunk in _renderingState.TerrainChunks)
            {
                SelectLOD(chunk.GrassLODs, grassConfig);
                SelectLOD(chunk.CropsLODs, cropsConfig);
            }
        }

        private void SelectLOD(TerrainChunk.RenderData[] lods, GameConfig.TerrainConfig.GrassLOD[] config)
        {
            // We can assume all LODs have almost the same center, so we just use the center of the first one
            var position = lods[0].Renderer.bounds.center;

            var viewSpacePosition = _scene.CinemachineCamera.transform.InverseTransformPoint(position);

            var selectedLod = int.MaxValue;
            for (var lod = 0; lod < config.Length; lod++)
                if (viewSpacePosition.z < config[lod].Threshold)
                {
                    selectedLod = lod;
                    break;
                }

            for (var lod = 0; lod < lods.Length; lod++) lods[lod].Renderer.enabled = lod == selectedLod;
        }
    }
}