Source code of the theme decals mod.

ThemeDecals.cs

using ColossalFramework.Plugins;
using ColossalFramework.UI;
using ICities;
using System.Collections.Generic;
using System.IO;
using System.Reflection;
using System.Xml.Serialization;
using UnityEngine;

namespace ThemeDecals
{
    public class ThemeDecalsMod : IUserMod
    {
        public string Name => "Theme Decals";
        public string Description => "Adds decals which match the current map theme.";
    }

    public class ThemeDecalsLoading : LoadingExtensionBase
    {
        public override void OnLevelUnloading()
        {
            base.OnLevelUnloading();
            ThemeDecals.Loaded = false;
        }
    }

    public class ThemeDecalsThreading : ThreadingExtensionBase
    {
        public override void OnUpdate(float realTimeDelta, float simulationTimeDelta)
        {
            base.OnUpdate(realTimeDelta, simulationTimeDelta);
            if (!ThemeDecals.Loaded && LoadingManager.instance.m_loadingComplete)
            {
                ThemeDecals.ApplyTextures();
                ThemeDecals.Loaded = true;
            }
        }
    }

    public class ThemeDecals
    {
        public static bool Loaded;

        internal static void ApplyTextures()
        {
            var terrain = UnityEngine.Object.FindObjectOfType<TerrainProperties>();
            for (uint i = 0; i < PrefabCollection<PropInfo>.LoadedCount(); i++)
            {
                var prefab = PrefabCollection<PropInfo>.GetLoaded(i);

                if (prefab == null) continue;

                if (prefab.m_mesh.name == "themedecal-cliff")
                {
                    prefab.m_material.SetTexture("_MainTex", terrain.m_cliffDiffuse);
                    prefab.m_lodMaterialCombined.SetTexture("_MainTex", terrain.m_cliffDiffuse);
                }
                else if (prefab.m_mesh.name == "themedecal-grass")
                {
                    prefab.m_material.SetTexture("_MainTex", terrain.m_grassDiffuse);
                    prefab.m_lodMaterialCombined.SetTexture("_MainTex", terrain.m_grassDiffuse);
                }
                else if (prefab.m_mesh.name == "themedecal-oil")
                {
                    prefab.m_material.SetTexture("_MainTex", terrain.m_oilDiffuse);
                    prefab.m_lodMaterialCombined.SetTexture("_MainTex", terrain.m_oilDiffuse);
                }
                else if (prefab.m_mesh.name == "themedecal-ore")
                {
                    prefab.m_material.SetTexture("_MainTex", terrain.m_oreDiffuse);
                    prefab.m_lodMaterialCombined.SetTexture("_MainTex", terrain.m_oreDiffuse);
                }
                else if (prefab.m_mesh.name == "themedecal-sand")
                {
                    prefab.m_material.SetTexture("_MainTex", terrain.m_sandDiffuse);
                    prefab.m_lodMaterialCombined.SetTexture("_MainTex", terrain.m_sandDiffuse);
                }
                else if (prefab.m_mesh.name == "themedecal-gravel")
                {
                    prefab.m_material.SetTexture("_MainTex", terrain.m_gravelDiffuse);
                    prefab.m_lodMaterialCombined.SetTexture("_MainTex", terrain.m_gravelDiffuse);
                }
                else if (prefab.m_mesh.name == "themedecal-ruined")
                {
                    prefab.m_material.SetTexture("_MainTex", terrain.m_ruinedDiffuse);
                    prefab.m_lodMaterialCombined.SetTexture("_MainTex", terrain.m_ruinedDiffuse);
                }
                else if (prefab.m_mesh.name == "themedecal-pavement")
                {
                    prefab.m_material.SetTexture("_MainTex", terrain.m_pavementDiffuse);
                    prefab.m_lodMaterialCombined.SetTexture("_MainTex", terrain.m_pavementDiffuse);
                }

                ApplyProperties();
            }
        }

        internal static void ApplyProperties()
        {
            for (uint i = 0; i < PrefabCollection<PropInfo>.LoadedCount(); i++)
            {
                var prefab = PrefabCollection<PropInfo>.GetLoaded(i);

                if (prefab == null) continue;

                if (prefab.m_mesh.name == "themedecal-cliff" ||
                    prefab.m_mesh.name == "themedecal-grass" ||
                    prefab.m_mesh.name == "themedecal-oil" ||
                    prefab.m_mesh.name == "themedecal-ore" ||
                    prefab.m_mesh.name == "themedecal-sand" ||
                    prefab.m_mesh.name == "themedecal-gravel" ||
                    prefab.m_mesh.name == "themedecal-ruined" ||
                    prefab.m_mesh.name == "themedecal-pavement")
                {
                    prefab.m_lodMaterial = prefab.m_material;
                    prefab.m_lodRenderDistance = 18000;
                }
            }
        }

    }
}