riversong-code-showcase/Source/Riversong/Game/World/Time/DayNightCycleLightingSystem.cs

using System;
using Cysharp.Threading.Tasks;
using UnityEngine;

namespace DanieleMarotta.RiversongCodeShowcase
{
    [RequiresWorldReadyForUpdate]
    [GameSystemGroup(typeof(LateGameSystemGroup))]
    [UpdateAfter(typeof(WorldTimeSystem))]
    public class DayNightCycleLightingSystem : GameSystem, IInitializable, IDisposable, IUpdatable
    {
        [InjectService]
        private GameConfig _config;

        [InjectService]
        private IScene _scene;

        [InjectService]
        private World _world;

        private Quaternion _initialLightRotation;

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

        public UniTask InitializeAsync()
        {
            _initialLightRotation = _scene.MainLight.transform.localRotation;

            return UniTask.CompletedTask;
        }

        public void Dispose()
        {
            Shader.SetGlobalFloat(ShaderProperties.NightBlend, 0);
        }

        public void Update()
        {
            var nightBlend = _world.TimeState.NightBlend;
            Shader.SetGlobalFloat(ShaderProperties.NightBlend, nightBlend);

            UpdateLightRig(nightBlend);
            UpdateShadows(nightBlend);
            UpdateAmbientLighting(nightBlend);
            UpdatePostProcessing(nightBlend);
        }

        private void UpdateLightRig(float nightBlend)
        {
            _scene.LightRig.transform.localRotation = _world.TimeState.DayNightCycleStep switch
            {
                DayNightCycleStep.Day => Quaternion.identity,
                DayNightCycleStep.DayToNight => Quaternion.Euler(0, nightBlend * 360, 0),
                DayNightCycleStep.Night => Quaternion.identity,
                DayNightCycleStep.NightToDay => Quaternion.Euler(0, -nightBlend * 360, 0),
                _ => throw new ArgumentException()
            };

            var dayRotation = _initialLightRotation;
            var nightRotation = _initialLightRotation * Quaternion.Euler(-90, 0, 0);

            _scene.MainLight.transform.localRotation = _world.TimeState.DayNightCycleStep switch
            {
                DayNightCycleStep.Day => dayRotation,
                DayNightCycleStep.DayToNight => Quaternion.Slerp(dayRotation, nightRotation, nightBlend),
                DayNightCycleStep.Night => nightRotation,
                DayNightCycleStep.NightToDay => Quaternion.Slerp(nightRotation, dayRotation, 1 - nightBlend),
                _ => throw new ArgumentException()
            };

            _scene.NightLight.transform.localRotation = _world.TimeState.DayNightCycleStep switch
            {
                DayNightCycleStep.Day => nightRotation,
                DayNightCycleStep.DayToNight => Quaternion.Slerp(nightRotation, dayRotation, nightBlend),
                DayNightCycleStep.Night => dayRotation,
                DayNightCycleStep.NightToDay => Quaternion.Slerp(dayRotation, nightRotation, 1 - nightBlend),
                _ => throw new ArgumentException()
            };
        }

        private void UpdateShadows(float nightBlend)
        {
            const float fadeSpeed = 2;

            var mainLightT = Mathf.Clamp01(fadeSpeed * nightBlend);
            UpdateShadows(_scene.MainLight, Mathf.Lerp(_config.Time.DayLighting.ShadowStrength, 0, mainLightT));

            var nightLightT = Mathf.Clamp01(fadeSpeed * (1 - nightBlend));
            UpdateShadows(_scene.NightLight, Mathf.Lerp(_config.Time.NightLighting.ShadowStrength, 0, nightLightT));
        }

        private static void UpdateShadows(Light light, float shadowStrength)
        {
            light.shadowStrength = shadowStrength;
            light.shadows = shadowStrength > 0 ? LightShadows.Soft : LightShadows.None;
        }

        private void UpdateAmbientLighting(float nightBlend)
        {
            RenderSettings.ambientLight = Color.Lerp(_config.Time.DayLighting.AmbientColor, _config.Time.NightLighting.AmbientColor, nightBlend);
        }

        private void UpdatePostProcessing(float nightBlend)
        {
            _scene.NightVolume.weight = nightBlend;
            _scene.BloomVolume.weight = nightBlend;
            _scene.WarmTintVolume.weight = GetWarmTintBlend();
        }

        private float GetWarmTintBlend()
        {
            var step = _world.TimeState.DayNightCycleStep;
            if (step != DayNightCycleStep.DayToNight && step != DayNightCycleStep.NightToDay) return 0;

            var config = _config.Time;

            var time = _world.TimeState.DayNightCycleTime;
            var blend = step == DayNightCycleStep.DayToNight ? Mathf.Clamp01(time / config.DayToNightDuration) : Mathf.Clamp01(time / config.NightToDayDuration);

            var rampUp = config.WarmTintRampUp;
            var rampDown = config.WarmTintRampDown;

            if (blend <= rampUp.x) return 0;
            if (blend < rampUp.y) return Mathf.SmoothStep(0, 1, Mathf.InverseLerp(rampUp.x, rampUp.y, blend));
            if (blend <= rampDown.x) return 1;
            if (blend < rampDown.y) return Mathf.SmoothStep(1, 0, Mathf.InverseLerp(rampDown.x, rampDown.y, blend));

            return 0;
        }
    }
}