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

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

namespace KeepersCompound.TMV;

public partial class Model : Node3D
{
    public override void _Ready()
    {
        var modelSelector = GetNode<Control>("%ModelSelector") as ModelSelector;
        modelSelector.LoadModel += BuildModel;
    }

    private void BuildModel(string rootPath, string modelPath)
    {
        foreach (var node in GetChildren())
        {
            node.QueueFree();
        }

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

        // TODO: Remove this disgusting hack
        var baseDir = ProjectSettings.GlobalizePath($"user://objects/tmp");
        var options = new EnumerationOptions
        {
            MatchCasing = MatchCasing.CaseInsensitive,
            RecurseSubdirectories = true,
        };
        var textures = new List<ImageTexture>();
        foreach (var material in modelFile.Materials)
        {
            var paths = Directory.GetFiles(baseDir, material.Name, options);
            if (paths.IsEmpty()) continue;

            var texture = TextureLoader.LoadTexture(paths[0]);
            var saveName = material.Name.GetBaseName() + ".png";
            texture.GetImage().SavePng(ProjectSettings.GlobalizePath($"user://debug/{saveName}"));
            textures.Add(texture);
        }

        var mat = new StandardMaterial3D
        {
            AlbedoTexture = textures[0]
        };

        // TODO: Support multiple materials and colour based materials
        var surfaceData = new 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
                {
                    var uv = (i % 4) switch
                    {
                        0 => new Vector2(0, 0),
                        1 => new Vector2(0, 1),
                        2 => new Vector2(1, 0),
                        3 => new Vector2(1, 1),
                        _ => throw new NotImplementedException(),
                    };
                    uvs.Add(uv);
                }

            }

            surfaceData.AddPolygon(vertices, normal, uvs, uvs);
        }
        var array = surfaceData.BuildSurfaceArray();

        var mesh = new ArrayMesh();
        mesh.AddSurfaceFromArrays(Mesh.PrimitiveType.Triangles, array);
        mesh.SurfaceSetMaterial(0, mat);

        var meshInstance = new MeshInstance3D { Mesh = mesh };
        AddChild(meshInstance);
    }
}