thief-mission-viewer/project/code/TMV/ModelLoader.cs

using System.Collections.Generic;
using System.IO;
using Godot;
using KeepersCompound.LGS;

namespace KeepersCompound.TMV;

public class ModelLoader
{
    private readonly Dictionary<(string, string), MeshInstance3D> _cache = new();

    public MeshInstance3D Load(string campaignName, string modelName, bool forceLoad = false)
    {
        campaignName ??= "";

        if (!forceLoad)
        {
            if (_cache.TryGetValue((campaignName, modelName), out var fmModel))
            {
                return fmModel?.Duplicate() as MeshInstance3D;
            }
            else if (_cache.TryGetValue(("", modelName), out var omModel))
            {
                return omModel?.Duplicate() as MeshInstance3D;
            }
        }

        // We don't care if this is null actually, we'll still cache that it's null lol
        var model = Timing.TimeStage("Load Models", () => { return LoadModel(ref campaignName, modelName); });
        _cache[(campaignName, modelName)] = model;
        return model?.Duplicate() as MeshInstance3D;
    }

    public static MeshInstance3D LoadModel(ref string campaignName, string modelName)
    {
        var pathManager = Context.Instance.PathManager;
        var (newCampaignName, modelPath) = pathManager.GetResourcePath(ResourceType.Object, campaignName, modelName);
        campaignName = newCampaignName;
        if (modelPath == null)
        {
            return null;
        }
        var modelFile = new ModelFile(modelPath);
        if (modelFile == null)
        {
            GD.Print($"Failed to load model file: {modelPath}");
            return null;
        }

        var materials = new List<StandardMaterial3D>();
        foreach (var material in modelFile.Materials)
        {
            if (material.Type == 0)
            {
                var resName = Path.GetFileNameWithoutExtension(material.Name);
                var (_, path) = pathManager.GetResourcePath(ResourceType.ObjectTexture, campaignName, resName);
                if (path == null)
                {
                    path = "user://textures/jorge.png";
                    GD.Print($"Failed to load model texture: {material.Name}");
                }

                var mat = new StandardMaterial3D
                {
                    AlbedoTexture = TextureLoader.LoadTexture(path),
                    Transparency = BaseMaterial3D.TransparencyEnum.AlphaDepthPrePass,
                };
                var name = material.Name.ToLower();
                for (var i = 0; i < 4; i++)
                {
                    if (name.Contains($"replace{i}"))
                    {
                        mat.SetMeta($"TxtRepl{i}", true);
                    }
                }

                materials.Add(mat);
            }
            else
            {
                var b = (material.Handle) & 0xff;
                var g = (material.Handle >> 8) & 0xff;
                var r = (material.Handle >> 16) & 0xff;
                var colour = new Color(r / 255.0f, g / 255.0f, b / 255.0f, 1.0f);
                materials.Add(new StandardMaterial3D
                {
                    AlbedoColor = colour
                });
            }
        }

        var surfaceDataMap = new Dictionary<int, MeshSurfaceData>();
        foreach (var poly in modelFile.Polygons)
        {
            var vertices = new List<Vector3>();
            var normal = modelFile.Normals[poly.Normal].ToGodotVec3();
            var uvs = new List<Vector2>();
            for (var i = 0; i < poly.VertexCount; i++)
            {
                var vertex = modelFile.Vertices[poly.VertexIndices[i]];
                vertices.Add(vertex.ToGodotVec3());
                if (i < poly.UvIndices.Length)
                {
                    var uv = modelFile.Uvs[poly.UvIndices[i]];
                    uvs.Add(new Vector2(uv.X, uv.Y));
                }
                else
                {
                    uvs.Add(Vector2.Zero);
                }
            }

            if (!surfaceDataMap.ContainsKey(poly.Data))
            {
                surfaceDataMap.Add(poly.Data, new MeshSurfaceData());
            }

            surfaceDataMap[poly.Data].AddPolygon(vertices, normal, uvs, uvs);
        }

        var mesh = new ArrayMesh();
        foreach (var (materialId, surfaceData) in surfaceDataMap)
        {
            var array = surfaceData.BuildSurfaceArray();
            var surfaceIdx = mesh.GetSurfaceCount();
            mesh.AddSurfaceFromArrays(Mesh.PrimitiveType.Triangles, array);
            for (var i = 0; i < materials.Count; i++)
            {
                var m = modelFile.Materials[i];
                if (m.Slot == materialId)
                {
                    mesh.SurfaceSetMaterial(surfaceIdx, materials[i]);
                    break;
                }
            }
        }

        var pos = -modelFile.Header.Center.ToGodotVec3();
        var meshInstance = new MeshInstance3D { Mesh = mesh, Position = pos };
        return meshInstance;
    }
}