https://www.nexusmods.com/eldenring/mods/2445

BlizzardMod.cs

// Created by thefifthmatt. All rights reserved.
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using SoulsIds;
using SoulsFormats;

namespace BlizzardMod
{
    // This uses DSMapStudio SoulsFormats, available standalone at
    // https://github.com/thefifthmatt/SoulsFormats/tree/dsms
    // SoulsIds is not all published yet, but is basic file-loading stuff.
    public class BlizzardMod
    {
        public static void Run(bool hidemap)
        {
            GameEditor game = new GameEditor(GameSpec.FromGame.ER);
            DCX.Type overrideDcx = DCX.Type.DCX_DFLT_11000_44_9;
            string outPath = "blizzard";

            string paramPath = $@"{game.Spec.GameDir}\{game.Spec.ParamFile}";
            Dictionary<string, PARAM> param = game.LoadParams(paramPath, game.LoadDefs());
            int baseId = 81;
            PARAM.Row baseRow = param["WeatherParam"][baseId];
            foreach (PARAM.Row row in param["WeatherParam"].Rows)
            {
                if (row.ID != baseId)
                {
                    GameEditor.CopyRow(baseRow, row);
                }
            }
            foreach (PARAM.Row row in param["CutsceneWeatherOverrideGparamConvertParam"].Rows)
            {
                row["weatherOverrideGparamId"].Value = baseId;
            }
            foreach (PARAM.Row row in param["CutsceneGparamWeatherParam"].Rows)
            {
                row["IndoorOutdoorType"].Value = (byte)0;
                foreach (PARAM.Cell cell in row.Cells)
                {
                    if (cell.Def.InternalName.StartsWith("Dst") && (short)cell.Value > 0)
                    {
                        cell.Value = 0;
                    }
                }
            }
            if (hidemap)
            {
                param["WorldMapPieceParam"].Rows.Clear();
                PARAM mapPoint = param["WorldMapPointParam"];
                mapPoint.Rows.RemoveAll(r => r.ID != 85495300 && r.ID != 111000);
                void addOpenPoint(int id, int x, int z)
                {
                    PARAM.Row row = GameEditor.AddRow(mapPoint, id, 111000);
                    row["areaNo"].Value = (byte)60;
                    row["gridXNo"].Value = (byte)x;
                    row["gridZNo"].Value = (byte)z;
                    row["posX"].Value = row["posY"].Value = row["posZ"].Value = 0f;
                }
                addOpenPoint(111008, 30, 30);
                addOpenPoint(111009, 64, 64);
            }
            game.OverrideBndRel(paramPath, $@"{outPath}\{game.Spec.ParamFile}", param, f => f.AppliedParamdef == null ? null : f.Write(), dcx: overrideDcx);

            foreach (string path in Directory.GetFiles($@"{game.Spec.GameDir}\event", "*.emevd.dcx"))
            {
                string map = GameEditor.BaseName(path);
                EMEVD emevd = EMEVD.Read(path);
                bool write = false;
                if (map == "common" && hidemap)
                {
                    EMEVD.Event newEvent = new EMEVD.Event(99559955);
                    newEvent.Instructions.AddRange(new[]
                    {
                        new EMEVD.Instruction(2003, 76, new List<object> { (byte)0, (byte)1, (byte)60, (byte)42, (byte)36, (byte)0, 0f, 0f, 0f }),
                        new EMEVD.Instruction(3, 0, new List<object> { (sbyte)0, (byte)1, (byte)0, 18000020 }),
                        new EMEVD.Instruction(2003, 78, new List<object> { 111008, 0f }),
                        new EMEVD.Instruction(2003, 78, new List<object> { 111009, 0f }),
                    });
                    emevd.Events.Add(newEvent);
                    EMEVD.Instruction init = new EMEVD.Instruction(2000, 0, new List<object> { 0, 99559955, 0 });
                    emevd.Events.Find(e => e.ID == 0).Instructions.Insert(0, init);
                    write = true;
                }
                foreach (EMEVD.Event ev in emevd.Events)
                {
                    for (int j = 0; j < ev.Instructions.Count; j++)
                    {
                        EMEVD.Instruction ins = ev.Instructions[j];
                        if (ins.Bank == 2012 && ins.ID == 11)
                        {
                            ev.Instructions[j] = new EMEVD.Instruction(1014, 18);
                            write = true;
                        }
                    }
                }
                string emevdPath = $@"{outPath}\event\{Path.GetFileName(path)}";
                if (write)
                {
                    emevd.Write(emevdPath, overrideDcx);
                }
                else if (File.Exists(emevdPath))
                {
                    File.Delete(emevdPath);
                }
            }

            foreach (string path in Directory.GetFiles($@"{game.Spec.GameDir}\{game.Spec.MsbDir}", "*.msb.dcx"))
            {
                string map = GameEditor.BaseName(path);
                MSBE msb = MSBE.Read(path);
                bool write = false;
                if (msb.Regions.EnvironmentMapEffectBoxes.Count > 0)
                {
                    HashSet<string> names = new HashSet<string>(msb.Regions.EnvironmentMapEffectBoxes.Select(r => r.Name));
                    msb.Regions.EnvironmentMapEffectBoxes.Clear();
                    foreach (MSBE.Region r in msb.Regions.GetEntries())
                    {
                        if (r.Shape is MSB.Shape.Composite comp && comp.Children.Any(c => names.Contains(c.RegionName)))
                        {
                            foreach (MSB.Shape.Composite.Child c in comp.Children)
                            {
                                if (names.Contains(c.RegionName))
                                {
                                    c.RegionName = null;
                                }
                            }
                        }
                    }
                    write = true;
                }
                foreach (MSBE.Part.Collision col in msb.Parts.Collisions)
                {
                    if (col.UnkT34 != 1)
                    {
                        col.UnkT34 = 1;
                        write = true;
                    }
                    MSBE.Part.SceneGparamConfig conf = col.SceneGparam;
                    if (conf != null)
                    {
                        conf.TransitionTime = -1;
                        conf.Unk18 = conf.Unk19 = conf.Unk1A = conf.Unk1B = conf.Unk1C = conf.Unk1D = conf.Unk20 = conf.Unk21 = -1;
                        write = true;
                    }
                }
                foreach (MSBE.Part.Asset asset in msb.Parts.Assets)
                {
                    if (asset.AssetUnk3.Unk0A != 0)
                    {
                        asset.AssetUnk3.Unk0A = 0;
                        write = true;
                    }
                }
                string msbPath = $@"{outPath}\{game.Spec.MsbDir}\{Path.GetFileName(path)}";
                if (write)
                {
                    msb.Write(msbPath, overrideDcx);
                }
                else if (File.Exists(msbPath))
                {
                    File.Delete(msbPath);
                }
            }
        }
    }
}