ThomagicRenderer/Runtime/Scripts/GrassRenderer.cs

using System.Collections.Generic;
using UnityEngine;

namespace Assets.ThoMagic.Renderer
{
    public class GrassRenderer : GrassStreamer
    {
       
        private readonly Terrain terrain;
        private readonly TerrainData terrainData;
        private bool isDirty;
        
        public GrassRenderer(Terrain terrain)
            : base(terrain)
        {
            this.terrain = terrain;
            terrainData = terrain.terrainData;
        }

        public void OnTerrainChanged(TerrainChangedFlags flags)
        {
            if (flags.HasFlag(TerrainChangedFlags.DelayedHeightmapUpdate))
                isDirty = true;
            else if (flags.HasFlag(TerrainChangedFlags.Heightmap))
                isDirty = true;
            else if (flags.HasFlag(TerrainChangedFlags.HeightmapResolution))
                isDirty = true;
            else if (flags.HasFlag(TerrainChangedFlags.Holes))
                isDirty = true;
            else if (flags.HasFlag(TerrainChangedFlags.DelayedHolesUpdate))
                isDirty = true;
            else if (flags.HasFlag(TerrainChangedFlags.FlushEverythingImmediately))
                isDirty = true;       
        }

        public void Destroy()
        {
            Recycle();
        }

        public void LateUpdate()
        {
            if (isDirty)
            {
                isDirty = false;
                Load();
            }

            if (Application.isEditor && !Application.isPlaying)
                RebuildChangedPrototypes();

            Update();
        }

        public void Load()
        {
            DetailPrototype[] detailPrototypes = terrainData.detailPrototypes;

            Recycle();

            int ownerHash = GetHashCode();

            if (grassPrefabs == null)
            {
                grassPrefabs = new List<int>();
                grassPrefabSet = new List<bool>();
            }

            float maxDetailDistance = float.MinValue;

            for (int index = 0; index < detailPrototypes.Length; ++index)
            {
                if (!detailPrototypes[index].usePrototypeMesh || detailPrototypes[index].prototype == null)
                {
                    AddDummy(index);
                }
                else
                {
                    GameObject prototypeToRender = RendererUtility.GetPrototypeToRender(detailPrototypes[index]);
                    if (!RendererUtility.SupportsProceduralInstancing(prototypeToRender))
                    {
                        AddDummy(index);
                    }
                    else
                    {
                        var settings = GetSettingsOrDefault(prototypeToRender);
                        maxDetailDistance = Mathf.Max(maxDetailDistance, settings.Settings.RenderDistance);
                        grassPrefabs.Add(RendererPool.RegisterObject(prototypeToRender, settings, this, ownerHash));
                        grassPrefabSet.Add(true);
                    }
                }
            }

            Build(maxDetailDistance, detailPrototypes.Length);
        }

        private void AddDummy(int i)
        {
            grassPrefabs.Add(-1);
            grassPrefabSet.Add(false);
        }

        public override void Recycle()
        {
            if (grassPrefabs == null)
                return;

            base.Recycle();

            int ownerHash = GetHashCode();
            for (int index = 0; index < grassPrefabs.Count; ++index)
            {
                if (grassPrefabSet[index])
                {
                    RendererPool.RemoveObject(grassPrefabs[index], ownerHash);
                }
            }

            grassPrefabs.Clear();  
            grassPrefabSet.Clear();
        }

        private void RebuildChangedPrototypes()
        {            
            DetailPrototype[] detailPrototypes = terrainData.detailPrototypes;
            if (detailPrototypes.Length != grassPrefabs.Count)
            {
                Load();
            }
            else
            {
                int ownerHash = GetHashCode();

                for (int index = 0; index < grassPrefabs.Count; ++index)
                {                    
                    if (grassPrefabSet[index])
                    {
                        GameObject prototypeToRender = RendererUtility.GetPrototypeToRender(detailPrototypes[index]);
                        GameObject gameObject = RendererPool.GetObject(grassPrefabs[index]);
                        if (prototypeToRender != gameObject)
                        {
                            RendererPool.RemoveObject(grassPrefabs[index], ownerHash);

                            if (prototypeToRender != null)
                            {
                                grassPrefabs[index] = RendererPool.RegisterObject(prototypeToRender, GetSettingsOrDefault(prototypeToRender), this, ownerHash);
                                grassPrefabSet[index] = true;
                            }
                            else
                            {
                                grassPrefabs[index] = -1;
                                grassPrefabSet[index] = false;
                            }
                        }
                        else if (RendererPool.ContentHashChanged(grassPrefabs[index]))
                        {
                            RendererPool.RemoveObject(grassPrefabs[index], GetHashCode());
                            if (prototypeToRender != null)
                            {
                                grassPrefabs[index] = RendererPool.RegisterObject(prototypeToRender, GetSettingsOrDefault(prototypeToRender), this, ownerHash);
                                grassPrefabSet[index] = true;
                            }
                            else
                            {
                                grassPrefabs[index] = -1;
                                grassPrefabSet[index] = false;
                            }
                        }
                        else if (prototypeToRender != null)
                            RendererPool.SetObjectSettings(prototypeToRender, GetSettingsOrDefault(prototypeToRender));
                    }
                }
            }
        }

        private IInstanceRenderSettings GetSettingsOrDefault(GameObject gameObject)
        {
            IInstanceRenderSettings instanceRenderSettings;
            return gameObject.TryGetComponent(out instanceRenderSettings) ? instanceRenderSettings : new DefaultRenderSettings();
        }

        private class DefaultRenderSettings : IInstanceRenderSettings
        {
            public InstanceRenderSettings Settings => new InstanceRenderSettings()
            {
                Render = true,
                DensityInDistance = 0.125f,
                DensityInDistanceFalloff = new Vector2(0.08f, 0.0075f),
                RenderDistance = 150f,
                ShadowDistance = 50f,
                Shadows = true,
                Supported = true
            };
        }      
    }
}