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

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

namespace KeepersCompound.TMV;

// TODO: Work out a way to share base game models again in the cache
public class ModelLoader
{
    public struct MeshDetails(int jointIdx, Transform3D transform, MeshInstance3D mesh)
    {
        public readonly int JointIdx = jointIdx;
        public readonly Transform3D Transform = transform;
        public readonly MeshInstance3D Mesh = mesh;
    }
    
    private readonly Dictionary<(string, string), MeshDetails[]> _cache = new();

    public MeshDetails[] Load(string modelName, bool forceLoad = false)
    {
        var campaignResources = Context.Instance.CampaignResources;
        var campaignName = campaignResources.name;
        campaignName ??= "";
        
        if (!forceLoad)
        {
            if (_cache.TryGetValue((campaignName, modelName), out var fmDetails))
            {
                return fmDetails;
            }
            if (_cache.TryGetValue(("", modelName), out var omDetails))
            {
                return omDetails;
            }
        }
        
        var details = Timing.TimeStage("Load Models", () => LoadModel(modelName));
        _cache[(campaignName, modelName)] = details;
        return details;
    }

    public static MeshInstance3D[] TransformMeshes(float[] joints, MeshDetails[] meshDetails)
    {
        var meshes = new List<MeshInstance3D>();
        foreach (var details in meshDetails)
        {
            var mesh = details.Mesh.Duplicate() as MeshInstance3D;
            if (details.JointIdx != -1)
            {
                var ang = float.DegreesToRadians(joints[details.JointIdx]);
                var r1 = new Quaternion(new Vector3(0, 0, 1), ang);
                var r2 = details.Transform.Basis.GetRotationQuaternion();
                var basis = new Basis(r2 * r1);
                mesh.SetTransform(new Transform3D(basis, details.Transform.Origin));
            }
            else
            {
                mesh.SetTransform(details.Transform);
            }
        
            meshes.Add(mesh);
        }

        return [..meshes];
    }

    public static MeshDetails[] LoadModel(string modelName)
    {
        var campaignResources = Context.Instance.CampaignResources;
        var modelPath = campaignResources.GetResourcePath(ResourceType.Object, modelName);
        if (modelPath == null)
        {
            return [];
        }

        var modelFile = new ModelFile(modelPath);
        if (modelFile == null)
        {
            GD.Print($"Failed to load model file: {modelPath}");
            return [];
        }

        var materials = new List<StandardMaterial3D>();
        foreach (var material in modelFile.Materials)
        {
            if (material.Type == 0)
            {
                var convertedName = ResourcePathManager.ConvertSeparator(material.Name);
                var resName = Path.GetFileNameWithoutExtension(convertedName);
                var path = campaignResources.GetResourcePath(ResourceType.ObjectTexture, resName);
                if (path == null)
                {
                    // Might fail in exported projects
                    path = "res://project/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 objCount = modelFile.Objects.Length;
        var meshDetails = new MeshDetails[objCount];
        for (var i = 0; i < objCount; i++)
        {
            var subObj = modelFile.Objects[i];
            var jointIdx = subObj.Joint;
            var transform = subObj.Type == 0 ? Transform3D.Identity : subObj.Transform.ToGodotTransform3D();
            var surfaceDataMap = new Dictionary<int, MeshSurfaceData>();
            foreach (var poly in modelFile.Polygons)
            {
                var v0 = poly.VertexIndices[0];
                if (v0 < subObj.PointIdx || v0 >= subObj.PointIdx + subObj.PointCount)
                {
                    continue;
                }
                
                var vertices = new List<Vector3>();
                var normal = modelFile.Normals[poly.Normal].ToGodotVec3();
                var uvs = new List<Vector2>();
                for (var j = 0; j < poly.VertexCount; j++)
                {
                    var vertex = modelFile.Vertices[poly.VertexIndices[j]];
                    vertices.Add(vertex.ToGodotVec3());
                    if (j < poly.UvIndices.Length)
                    {
                        var uv = modelFile.Uvs[poly.UvIndices[j]];
                        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 j = 0; j < materials.Count; j++)
                {
                    var m = modelFile.Materials[j];
                    if (m.Slot == materialId)
                    {
                        mesh.SurfaceSetMaterial(surfaceIdx, materials[j]);
                        break;
                    }
                }
            }

            var pos = -modelFile.Header.Center.ToGodotVec3();
            var meshInstance = new MeshInstance3D { Mesh = mesh, Position = pos };
            meshDetails[i] = new MeshDetails(jointIdx, transform, meshInstance);
        }

        return meshDetails;
    }
}