Refactor HelixViewer extend format support

QuickLook.Plugin/QuickLook.Plugin.HelixViewer/HelixPanel.Import.cs

@@ -0,0 +1,104 @@
+// Copyright © 2017-2025 QL-Win Contributors
+//
+// This file is part of QuickLook program.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+using Assimp;
+using HelixToolkit.Wpf;
+using System;
+using System.IO;
+using System.Linq;
+using System.Windows.Media;
+using System.Windows.Media.Media3D;
+
+namespace QuickLook.Plugin.HelixViewer;
+
+public partial class HelixPanel
+{
+    private void Load()
+    {
+        var importerType = Importer.GetImporterType(_path);
+
+        try
+        {
+            if (importerType == ImporterType.Extended)
+            {
+                var context = new AssimpContext();
+                var scene = context.ImportFile(_path, PostProcessSteps.Triangulate);
+
+                foreach (var mesh in scene.Meshes)
+                {
+                    var geometry = new MeshGeometry3D()
+                    {
+                        Positions = [.. mesh.Vertices.Select(v => new Point3D(v.X, v.Y, v.Z))],
+                        TriangleIndices = [.. mesh.GetIndices()],
+                    };
+                    var model = new GeometryModel3D()
+                    {
+                        Geometry = geometry,
+                        Material = Materials.Gray,
+                    };
+
+                    modelVisual.Content = model;
+                }
+            }
+            else
+            {
+                var modelImporter = new ModelImporter();
+                var model3DGroup = modelImporter.Load(_path);
+                var diffuseMaterial = new DiffuseMaterial(new SolidColorBrush(Color.FromRgb(0xA0, 0xA0, 0xA0)));
+
+                foreach (GeometryModel3D child in model3DGroup.Children.Cast<GeometryModel3D>())
+                {
+                    child.Material = diffuseMaterial;
+                    child.BackMaterial = diffuseMaterial;
+                }
+
+                modelVisual.Content = model3DGroup;
+            }
+        }
+        catch (Exception ex)
+        {
+            errorInfo.Text = $"[{nameof(ImporterType)}.{importerType}] {ex}";
+            errorInfo.Visibility = System.Windows.Visibility.Visible;
+            viewer.Visibility = System.Windows.Visibility.Collapsed;
+        }
+    }
+}
+
+file static class Importer
+{
+    public static ImporterType GetImporterType(string path)
+    {
+        if (string.IsNullOrEmpty(path))
+            return ImporterType.Unknown;
+
+        return Path.GetExtension(path).ToLower() switch
+        {
+            ".stl" or ".obj" or ".3ds" or ".lwo" or ".ply" => ImporterType.Default,
+            ".fbx" or ".3mf" or ".glb" or ".gltf" or ".dae" or ".dxf" => ImporterType.Extended,
+            ".pmx" => ImporterType.Extended_MMD,
+            _ => ImporterType.Unknown,
+        };
+    }
+}
+
+file enum ImporterType
+{
+    Unknown,
+    Default,
+    Extended,
+    Extended_MMD,
+}