HelixViewerPanel.xaml.cs

using HelixToolkit.Wpf;
using MMDExtensions;
using MMDExtensions.PMX;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Media.Media3D;

namespace QuickLook.Plugin.HelixViewer
{
    public partial class HelixViewerPanel : UserControl
    {
        private PMXFormat format_;
        public HelixViewerPanel(string path)
        {
            InitializeComponent();

            var builder = new MeshBuilder();

            format_ = LoadPmxMaterials(path);
            MeshCreationInfo creation_info = CreateMeshCreationInfoSingle();


            var mats = format_.material_list.material.Length;

            var models = new Model3DGroup();

            for (int i = 0, i_max = creation_info.value.Length; i < i_max; ++i)
            {
                //format_.face_vertex_list.face_vert_indexを[start](含む)から[start+count](含まず)迄取り出し
                int[] indices = creation_info.value[i].plane_indices.Select(x => (int)creation_info.reassign_dictionary[x]) //頂点リアサインインデックス変換
                                                                    .ToArray();
                MeshGeometry3D mesh = new MeshGeometry3D();

                mesh.Positions = new Point3DCollection(format_.vertex_list.vertex.Select(x => x.pos));

                mesh.TextureCoordinates = new PointCollection(format_.vertex_list.vertex.Select(x => x.uv));

                indices.ToList()
                    .ForEach(x => mesh.TriangleIndices.Add(x));

                var textureIndex = format_.material_list.material[i].usually_texture_index;

                Material material;

                if (textureIndex == uint.MaxValue)
                {
                    material = new DiffuseMaterial(new SolidColorBrush(Color.FromRgb(160, 160, 160)));
                }
                else
                {
                    //  Texture
                    ImageBrush colors_brush = new ImageBrush
                    {
                        ImageSource = new BitmapImage(
                            new Uri(Path.Combine(format_.meta_header.folder,
                            format_.texture_list.texture_file[textureIndex]), UriKind.Relative))
                    };
                    material =
                        new DiffuseMaterial(colors_brush);
                }

                var model = new GeometryModel3D(mesh, material);
                model.BackMaterial = material;
                models.Children.Add(model);
            }
            PreviewModel.Content = models;
        }
        public static PMXFormat LoadPmxMaterials(string path)
        {
            return PMXLoaderScript.Import(path);
        }

        MeshCreationInfo CreateMeshCreationInfoSingle()
        {
            MeshCreationInfo result = new MeshCreationInfo();
            //全マテリアルを設定
            result.value = CreateMeshCreationInfoPacks();
            //全頂点を設定
            result.all_vertices = Enumerable.Range(0, format_.vertex_list.vertex.Length).Select(x => (uint)x).ToArray();
            //頂点リアサインインデックス用辞書作成
            result.reassign_dictionary = new Dictionary<uint, uint>(result.all_vertices.Length);
            for (uint i = 0, i_max = (uint)result.all_vertices.Length; i < i_max; ++i)
            {
                result.reassign_dictionary[i] = i;
            }
            return result;
        }
        MeshCreationInfo.Pack[] CreateMeshCreationInfoPacks()
        {
            uint plane_start = 0;
            //マテリアル単位のMeshCreationInfo.Packを作成する
            return Enumerable.Range(0, format_.material_list.material.Length)
                            .Select(x =>
                            {
                                MeshCreationInfo.Pack pack = new MeshCreationInfo.Pack();
                                pack.material_index = (uint)x;
                                uint plane_count = format_.material_list.material[x].face_vert_count;
                                pack.plane_indices = format_.face_vertex_list.face_vert_index.Skip((int)plane_start)
                                                                                                        .Take((int)plane_count)
                                                                                                        .ToArray();
                                pack.vertices = pack.plane_indices.Distinct() //重複削除
                                                                        .ToArray();
                                plane_start += plane_count;
                                return pack;
                            })
                            .ToArray();
        }
    }
}

public class MeshCreationInfo
{
    public class Pack
    {
        public uint material_index; //マテリアル
        public uint[] plane_indices;    //面
        public uint[] vertices;     //頂点
    }
    public Pack[] value;
    public uint[] all_vertices;         //総頂点
    public Dictionary<uint, uint> reassign_dictionary;  //頂点リアサインインデックス用辞書
}