Add sub-asset import and mesh asset support

- Implement sub-asset import for mesh/model assets with manifest generation and deterministic GUIDs
- Extend AssetCatalog for sub-asset tracking and management
- Update AssetRegistry and ImportCoordinator for sub-asset workflows
- Add mesh asset parsing, GPU upload, and resource management
- Update mesh data structures for meshlet groups/hierarchy and LODs
- Improve tests for sub-asset import and mesh handling
- Enhance mocks for mesh asset testing and resource mapping
- Fix path handling and native DLL loading issues
- Miscellaneous bug fixes and refactoring

src/Editor/Ghost.Editor.Core/Assets/AssetHandler.cs

@@ -49,7 +49,14 @@ public interface IImportableAssetHandler : IAssetHandler
     ValueTask<Result> ExportAsync(string assetPath, string targetPath, IAssetExportOptions? options, CancellationToken token = default);
 }
 
+public readonly record struct ImportedSubAsset(Guid Guid, string Kind, string DisplayName, string StablePath, string VirtualSourcePath, Guid HandlerTypeId);
+
+public interface ISubAssetImportableAssetHandler : IImportableAssetHandler
+{
+    ValueTask<Result<ImportedSubAsset[]>> ImportWithSubAssetsAsync(string sourcePath, string targetPath, Guid id, IAssetSettings? settings, CancellationToken token = default);
+}
+
 public interface IPackableAssetHandler : IAssetHandler
 {
     ValueTask<Result> PackAsync(string assetPath, MemoryStream targetStream, CancellationToken token = default);
-}
+}

src/Editor/Ghost.Editor.Core/Assets/AssetMeta.cs

@@ -69,7 +69,7 @@ internal static class AssetMetaIO
     public const string META_EXTENSION_NAME = "gmeta";
     public const string META_EXTENSION = ".gmeta";
 
-    private static readonly JsonSerializerOptions s_options = new()
+    internal static readonly JsonSerializerOptions s_options = new()
     {
         WriteIndented = true,
         PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
@@ -136,6 +136,7 @@ internal static class AssetMetaIO
         }
 
         File.Move(tempPath, metaPath);
+
     }
 
     public static string GetMetaPath(string sourceFilePath)

src/Editor/Ghost.Editor.Core/Assets/MeshAssetHandler.cs

@@ -1,9 +1,17 @@
 using Ghost.Core;
 using Ghost.Engine;
+using Ghost.Editor.Core.Services;
+using Ghost.Graphics.Core;
 using Ghost.Graphics.RHI;
+using Misaki.HighPerformance.LowLevel.Buffer;
 using Misaki.HighPerformance.LowLevel.Collections;
 using Misaki.HighPerformance.Mathematics;
+using Misaki.HighPerformance.Mathematics.Geometry;
+using System.IO.Hashing;
+using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
+using System.Text;
+using System.Text.Json;
 
 namespace Ghost.Editor.Core.Assets;
 
@@ -132,6 +140,139 @@ public class LightMeshNode : MeshNode
     }
 }
 
+public sealed class ModelManifest
+{
+    public Guid AssetId
+    {
+        get; set;
+    }
+
+    public ModelManifestNode Root
+    {
+        get; set;
+    } = new ModelManifestNode();
+
+    public List<ModelManifestSubAsset> Meshes
+    {
+        get; set;
+    } = new List<ModelManifestSubAsset>();
+
+    public List<ModelManifestMetadata> Metadata
+    {
+        get; set;
+    } = new List<ModelManifestMetadata>();
+}
+
+public sealed class ModelManifestNode
+{
+    public string Name
+    {
+        get; set;
+    } = string.Empty;
+
+    public string StablePath
+    {
+        get; set;
+    } = string.Empty;
+
+    public float4x4 LocalTransform
+    {
+        get; set;
+    }
+
+    public Guid MeshGuid
+    {
+        get; set;
+    }
+
+    public List<ModelManifestNode> Children
+    {
+        get; set;
+    } = new List<ModelManifestNode>();
+}
+
+public sealed class ModelManifestSubAsset
+{
+    public Guid Guid
+    {
+        get; set;
+    }
+
+    public string Name
+    {
+        get; set;
+    } = string.Empty;
+
+    public string StablePath
+    {
+        get; set;
+    } = string.Empty;
+
+    public int MaterialSlotCount
+    {
+        get; set;
+    }
+
+    public int VertexCount
+    {
+        get; set;
+    }
+
+    public int IndexCount
+    {
+        get; set;
+    }
+}
+
+public sealed class ModelManifestMetadata
+{
+    public string Kind
+    {
+        get; set;
+    } = string.Empty;
+
+    public string Name
+    {
+        get; set;
+    } = string.Empty;
+
+    public string StablePath
+    {
+        get; set;
+    } = string.Empty;
+}
+
+internal sealed class ImportedModelAsset : IAsset
+{
+    public Guid ID
+    {
+        get;
+    }
+
+    public Guid TypeID => typeof(FBXAsset).GUID;
+
+    public IAssetSettings? Settings
+    {
+        get;
+    }
+
+    public ModelManifest Manifest
+    {
+        get;
+    }
+
+    public ImportedModelAsset(Guid id, IAssetSettings? settings, ModelManifest manifest)
+    {
+        ID = id;
+        Settings = settings;
+        Manifest = manifest;
+    }
+
+    public void Dispose()
+    {
+    }
+}
+
 public abstract class MeshAsset : IAsset
 {
     private MeshNode _root;
@@ -240,7 +381,8 @@ internal class FbxAssetSettings : MeshAssetSettings
 {
 }
 
-internal class FBXAssetHandler : IImportableAssetHandler, IPackableAssetHandler
+[CustomAssetHandler(FBXAsset.GUID, [".fbx", ".obj"], 1)]
+internal class FBXAssetHandler : ISubAssetImportableAssetHandler, IPackableAssetHandler
 {
     public AssetType RuntimeAssetType => AssetType.Mesh;
 
@@ -250,31 +392,326 @@ internal class FBXAssetHandler : IImportableAssetHandler, IPackableAssetHandler
 
     public IAssetSettings? CreateDefaultSettings()
     {
-        throw new NotImplementedException();
+        return new FbxAssetSettings();
     }
 
-    public ValueTask<Result<IAsset>> LoadAssetAsync(string assetPath, Guid id, IAssetSettings? settings, CancellationToken token = default)
+    public async ValueTask<Result<IAsset>> LoadAssetAsync(string assetPath, Guid id, IAssetSettings? settings, CancellationToken token = default)
     {
-        throw new NotImplementedException();
+        var importedPath = ImportCoordinator.GetImportedAssetPath(id);
+        if (!File.Exists(importedPath))
+        {
+            return Result.Failure<IAsset>("Imported model manifest does not exist.");
+        }
+
+        try
+        {
+            await using var stream = new FileStream(importedPath, FileMode.Open, FileAccess.Read, FileShare.Read);
+            var manifest = await JsonSerializer.DeserializeAsync<ModelManifest>(stream, cancellationToken: token).ConfigureAwait(false);
+            return manifest != null
+                ? Result.Success<IAsset>(new ImportedModelAsset(id, settings, manifest))
+                : Result.Failure<IAsset>("Failed to deserialize model manifest.");
+        }
+        catch (Exception ex)
+        {
+            return Result.Failure<IAsset>(ex.Message);
+        }
     }
 
     public ValueTask<Result> SaveAssetAsync(string targetPath, IAsset asset, CancellationToken token = default)
     {
-        throw new NotImplementedException();
+        return ValueTask.FromResult(Result.Failure("Saving model assets is not supported yet."));
     }
 
-    public ValueTask<Result> ImportAsync(string sourcePath, string targetPath, Guid id, IAssetSettings? settings, CancellationToken token = default)
+    public async ValueTask<Result> ImportAsync(string sourcePath, string targetPath, Guid id, IAssetSettings? settings, CancellationToken token = default)
     {
-        throw new NotImplementedException();
+        return await ImportWithSubAssetsAsync(sourcePath, targetPath, id, settings, token).ConfigureAwait(false);
+    }
+
+    public async ValueTask<Result<ImportedSubAsset[]>> ImportWithSubAssetsAsync(string sourcePath, string targetPath, Guid id, IAssetSettings? settings, CancellationToken token = default)
+    {
+        if (!File.Exists(sourcePath))
+        {
+            return Result.Failure<ImportedSubAsset[]>("Source file does not exist.");
+        }
+
+        var meshSettings = ResolveSettings(sourcePath, settings);
+        var root = new MeshNode();
+        try
+        {
+            var parseJob = new MeshParsingJob(root, sourcePath, AllocationHandle.Persistent, meshSettings);
+            var context = default(Misaki.HighPerformance.Jobs.JobExecutionContext);
+            parseJob.Execute(in context);
+
+            var manifest = new ModelManifest
+            {
+                AssetId = id,
+            };
+
+            var importedSubAssets = new List<ImportedSubAsset>();
+            manifest.Root = await WriteNodeAsync(id, sourcePath, root, string.Empty, manifest, importedSubAssets, token).ConfigureAwait(false);
+
+            Directory.CreateDirectory(Path.GetDirectoryName(targetPath)!);
+            await using (var stream = new FileStream(targetPath, FileMode.Create, FileAccess.Write, FileShare.None))
+            {
+                await JsonSerializer.SerializeAsync(stream, manifest, cancellationToken: token).ConfigureAwait(false);
+            }
+
+            return importedSubAssets.ToArray();
+        }
+        catch (Exception ex)
+        {
+            return Result.Failure<ImportedSubAsset[]>($"Failed to import mesh asset: {ex.Message}");
+        }
+        finally
+        {
+            root.Dispose();
+        }
     }
 
     public ValueTask<Result> ExportAsync(string assetPath, string targetPath, IAssetExportOptions? options, CancellationToken token = default)
     {
-        throw new NotImplementedException();
+        return ValueTask.FromResult(Result.Failure("Exporting model assets is not supported yet."));
     }
 
     public ValueTask<Result> PackAsync(string assetPath, MemoryStream targetStream, CancellationToken token = default)
     {
-        throw new NotImplementedException();
+        return ValueTask.FromResult(Result.Failure("Packing model assets is not supported yet."));
     }
-}
+
+    private static MeshAssetSettings ResolveSettings(string sourcePath, IAssetSettings? settings)
+    {
+        if (settings is MeshAssetSettings meshSettings)
+        {
+            return meshSettings;
+        }
+
+        return Path.GetExtension(sourcePath).Equals(".obj", StringComparison.OrdinalIgnoreCase)
+            ? new ObjAssetSettings()
+            : new FbxAssetSettings();
+    }
+
+    private static async ValueTask<ModelManifestNode> WriteNodeAsync(
+        Guid parentGuid,
+        string sourcePath,
+        MeshNode node,
+        string parentPath,
+        ModelManifest manifest,
+        List<ImportedSubAsset> importedSubAssets,
+        CancellationToken token)
+    {
+        token.ThrowIfCancellationRequested();
+
+        var stablePath = string.IsNullOrEmpty(parentPath)
+            ? SanitizePathSegment(node.Name)
+            : $"{parentPath}/{SanitizePathSegment(node.Name)}";
+
+        var manifestNode = new ModelManifestNode
+        {
+            Name = node.Name,
+            StablePath = stablePath,
+            LocalTransform = node.LocalTransform,
+        };
+
+        if (node is GeometryMeshNode geometry)
+        {
+            var meshGuid = CreateDeterministicSubAssetGuid(parentGuid, "Mesh", stablePath);
+            var meshPath = ImportCoordinator.GetImportedAssetPath(meshGuid);
+            Directory.CreateDirectory(Path.GetDirectoryName(meshPath)!);
+
+            var meshInfo = await WriteMeshContentAsync(meshPath, geometry, token).ConfigureAwait(false);
+            manifestNode.MeshGuid = meshGuid;
+
+            manifest.Meshes.Add(new ModelManifestSubAsset
+            {
+                Guid = meshGuid,
+                Name = node.Name,
+                StablePath = stablePath,
+                MaterialSlotCount = meshInfo.materialSlotCount,
+                VertexCount = geometry.Vertices.Count,
+                IndexCount = geometry.Indices.Count,
+            });
+
+            importedSubAssets.Add(new ImportedSubAsset(
+                meshGuid,
+                "Mesh",
+                node.Name,
+                stablePath,
+                $"{sourcePath}#Mesh/{stablePath}",
+                typeof(FBXAsset).GUID));
+        }
+        else if (node is LightMeshNode)
+        {
+            manifest.Metadata.Add(new ModelManifestMetadata
+            {
+                Kind = "Light",
+                Name = node.Name,
+                StablePath = stablePath,
+            });
+        }
+
+        foreach (var child in node.Children)
+        {
+            manifestNode.Children.Add(await WriteNodeAsync(parentGuid, sourcePath, child, stablePath, manifest, importedSubAssets, token).ConfigureAwait(false));
+        }
+
+        return manifestNode;
+    }
+
+    private static ValueTask<(int materialSlotCount, int lodLevelCount)> WriteMeshContentAsync(string targetPath, GeometryMeshNode geometry, CancellationToken token)
+    {
+        unsafe
+        {
+            var meshletData = new MeshletMeshData();
+            try
+            {
+                MeshProcessor.BuildMeshlets(&meshletData, geometry.Vertices.AsReadOnly(), geometry.Indices.AsReadOnly(), geometry.MaterialParts.AsSpan());
+                MeshProcessor.BuildClusterLodHierarchy(&meshletData);
+
+                var bounds = ComputeBounds(geometry.Vertices);
+                var header = new MeshContentHeader
+                {
+                    magic = MeshContentHeader.MAGIC,
+                    version = MeshContentHeader.VERSION,
+                    vertexCount = (uint)geometry.Vertices.Count,
+                    indexCount = (uint)geometry.Indices.Count,
+                    materialPartCount = (uint)geometry.MaterialParts.Length,
+                    meshletCount = (uint)meshletData.meshlets.Count,
+                    meshletGroupCount = (uint)meshletData.groups.Count,
+                    meshletHierarchyNodeCount = (uint)meshletData.hierarchyNodes.Count,
+                    meshletVertexCount = (uint)meshletData.meshletVertices.Count,
+                    meshletTriangleCount = (uint)meshletData.meshletTriangles.Count,
+                    materialSlotCount = (uint)meshletData.materialSlotCount,
+                    lodLevelCount = (uint)meshletData.lodLevelCount,
+                    boundsMin = bounds.Min,
+                    boundsMax = bounds.Max,
+                };
+
+                using var stream = new FileStream(targetPath, FileMode.Create, FileAccess.Write, FileShare.None);
+                WriteStruct(stream, in header);
+
+                header.vertexOffset = (ulong)stream.Position;
+                WriteSpan(stream, geometry.Vertices.AsSpan());
+
+                header.indexOffset = (ulong)stream.Position;
+                WriteSpan(stream, geometry.Indices.AsSpan());
+
+                header.materialPartOffset = (ulong)stream.Position;
+                WriteMaterialParts(stream, geometry.MaterialParts.AsSpan());
+
+                header.meshletOffset = (ulong)stream.Position;
+                WriteSpan(stream, meshletData.meshlets.AsSpan());
+
+                header.meshletGroupOffset = (ulong)stream.Position;
+                WriteSpan(stream, meshletData.groups.AsSpan());
+
+                header.meshletHierarchyNodeOffset = (ulong)stream.Position;
+                WriteSpan(stream, meshletData.hierarchyNodes.AsSpan());
+
+                header.meshletVertexOffset = (ulong)stream.Position;
+                WriteSpan(stream, meshletData.meshletVertices.AsSpan());
+
+                header.meshletTriangleOffset = (ulong)stream.Position;
+                WriteSpan(stream, meshletData.meshletTriangles.AsSpan());
+
+                stream.Position = 0;
+                WriteStruct(stream, in header);
+                stream.Flush();
+
+                return ValueTask.FromResult((meshletData.materialSlotCount, meshletData.lodLevelCount));
+            }
+            finally
+            {
+                meshletData.Dispose();
+            }
+        }
+    }
+
+    private static AABB ComputeBounds(UnsafeList<Vertex> vertices)
+    {
+        var min = new float3(float.MaxValue);
+        var max = new float3(float.MinValue);
+        for (var i = 0; i < vertices.Count; i++)
+        {
+            var p = vertices[i].position;
+            min = math.min(min, p);
+            max = math.max(max, p);
+        }
+
+        return new AABB(min, max);
+    }
+
+    private static Guid CreateDeterministicSubAssetGuid(Guid parentGuid, string kind, string stablePath)
+    {
+        var bytes = Encoding.UTF8.GetBytes($"{parentGuid:N}:{kind}:{stablePath}");
+        Span<byte> hash = stackalloc byte[16];
+        var hashValue = XxHash128.HashToUInt128(bytes);
+        Unsafe.WriteUnaligned(ref hash[0], hashValue);
+
+        hash[6] = (byte)((hash[6] & 0x0F) | 0x50);
+        hash[8] = (byte)((hash[8] & 0x3F) | 0x80);
+        return new Guid(hash);
+    }
+
+    private static string SanitizePathSegment(string value)
+    {
+        if (string.IsNullOrWhiteSpace(value))
+        {
+            return "Node";
+        }
+
+        var chars = value.ToCharArray();
+        for (var i = 0; i < chars.Length; i++)
+        {
+            if (chars[i] == '/' || chars[i] == '\\' || chars[i] == '#')
+            {
+                chars[i] = '_';
+            }
+        }
+
+        return new string(chars);
+    }
+
+    private static void WriteMaterialParts(Stream stream, ReadOnlySpan<MaterialPartInfo> parts)
+    {
+        if (parts.IsEmpty)
+        {
+            return;
+        }
+
+        Span<MeshContentMaterialPart> buffer = parts.Length <= 64
+            ? stackalloc MeshContentMaterialPart[parts.Length]
+            : new MeshContentMaterialPart[parts.Length];
+
+        for (var i = 0; i < parts.Length; i++)
+        {
+            buffer[i] = new MeshContentMaterialPart
+            {
+                materialIndex = parts[i].materialIndex,
+                indexStart = parts[i].indexStart,
+                indexCount = parts[i].indexCount,
+                vertexStart = parts[i].vertexStart,
+                vertexCount = parts[i].vertexCount,
+            };
+        }
+
+        WriteSpan(stream, buffer);
+    }
+
+    private static void WriteStruct<T>(Stream stream, ref readonly T value)
+        where T : unmanaged
+    {
+        var span = MemoryMarshal.AsBytes(MemoryMarshal.CreateReadOnlySpan(in value, 1));
+        stream.Write(span);
+    }
+
+    private static void WriteSpan<T>(Stream stream, ReadOnlySpan<T> value)
+        where T : unmanaged
+    {
+        if (value.IsEmpty)
+        {
+            return;
+        }
+
+        stream.Write(MemoryMarshal.AsBytes(value));
+    }
+}

src/Editor/Ghost.Editor.Core/Services/AssetCatalog.cs

@@ -9,6 +9,8 @@ namespace Ghost.Editor.Core.Services;
 /// </summary>
 public sealed partial class AssetCatalog : IDisposable
 {
+    public readonly record struct SubAssetInfo(Guid Guid, Guid ParentGuid, string Kind, string DisplayName, string StablePath, string SourcePath, Guid HandlerTypeId);
+
     private readonly SqliteConnection _connection;
     private readonly Lock _writeLock = new();
 
@@ -26,6 +28,8 @@ public sealed partial class AssetCatalog : IDisposable
     private readonly SqliteCommand _cmdInsertDep;
     private readonly SqliteCommand _cmdClearDeps;
     private readonly SqliteCommand _cmdEnumerate;
+    private readonly SqliteCommand _cmdEnumerateSubAssets;
+    private readonly SqliteCommand _cmdDeleteSubAssetsForParent;
 
     public AssetCatalog(string dbPath)
     {
@@ -54,15 +58,19 @@ public sealed partial class AssetCatalog : IDisposable
         _cmdGetImportedAt = CreateCommand("SELECT imported_at_ms FROM assets WHERE guid = @guid");
 
         _cmdUpsert = CreateCommand(@"
-            INSERT INTO assets (guid, source_path, handler_type_id, handler_version, content_hash, settings_hash, imported_at_ms)
+            INSERT INTO assets (guid, source_path, handler_type_id, handler_version, content_hash, settings_hash, imported_at_ms, parent_guid, subasset_kind, display_name, stable_path)
-            VALUES (@guid, @path, @handler_id, @version, @content_hash, @settings_hash, @imported_at_ms)
+            VALUES (@guid, @path, @handler_id, @version, @content_hash, @settings_hash, @imported_at_ms, @parent_guid, @subasset_kind, @display_name, @stable_path)
             ON CONFLICT(guid) DO UPDATE SET
                 source_path = excluded.source_path,
                 handler_type_id = excluded.handler_type_id,
                 handler_version = excluded.handler_version,
                 content_hash = excluded.content_hash,
                 settings_hash = excluded.settings_hash,
-                imported_at_ms = excluded.imported_at_ms");
+                imported_at_ms = excluded.imported_at_ms,
+                parent_guid = excluded.parent_guid,
+                subasset_kind = excluded.subasset_kind,
+                display_name = excluded.display_name,
+                stable_path = excluded.stable_path");
         _cmdDelete = CreateCommand("DELETE FROM assets WHERE guid = @guid");
         _cmdGetReferencers = CreateCommand("SELECT from_guid FROM dependencies WHERE to_guid = @guid");
         _cmdGetDependencies = CreateCommand("SELECT to_guid FROM dependencies WHERE from_guid = @guid");
@@ -70,6 +78,8 @@ public sealed partial class AssetCatalog : IDisposable
         _cmdInsertDep = CreateCommand("INSERT INTO dependencies (from_guid, to_guid) VALUES (@from, @to)");
         _cmdClearDeps = CreateCommand("DELETE FROM dependencies WHERE from_guid = @guid");
         _cmdEnumerate = CreateCommand("SELECT guid, source_path FROM assets");
+        _cmdEnumerateSubAssets = CreateCommand("SELECT guid, parent_guid, subasset_kind, display_name, stable_path, source_path, handler_type_id FROM assets WHERE parent_guid = @parent_guid ORDER BY stable_path");
+        _cmdDeleteSubAssetsForParent = CreateCommand("DELETE FROM assets WHERE parent_guid = @parent_guid");
     }
 
     private SqliteCommand CreateCommand(string sql)
@@ -90,9 +100,14 @@ public sealed partial class AssetCatalog : IDisposable
                 handler_version INTEGER NOT NULL DEFAULT 0,
                 content_hash    TEXT,
                 settings_hash   TEXT,
-                imported_at_ms  INTEGER
+                imported_at_ms  INTEGER,
+                parent_guid     BLOB(16),
+                subasset_kind   TEXT,
+                display_name    TEXT,
+                stable_path     TEXT
             );
             CREATE UNIQUE INDEX IF NOT EXISTS idx_assets_path ON assets(source_path);
+            CREATE INDEX IF NOT EXISTS idx_assets_parent ON assets(parent_guid);
 
             CREATE TABLE IF NOT EXISTS dependencies (
                 from_guid   BLOB(16) NOT NULL REFERENCES assets(guid) ON DELETE CASCADE,
@@ -108,6 +123,28 @@ public sealed partial class AssetCatalog : IDisposable
             );
             CREATE INDEX IF NOT EXISTS idx_labels_label ON labels(label);";
         cmd.ExecuteNonQuery();
+
+        TryAddColumn("assets", "parent_guid", "BLOB(16)");
+        TryAddColumn("assets", "subasset_kind", "TEXT");
+        TryAddColumn("assets", "display_name", "TEXT");
+        TryAddColumn("assets", "stable_path", "TEXT");
+
+        using var indexCmd = _connection.CreateCommand();
+        indexCmd.CommandText = "CREATE INDEX IF NOT EXISTS idx_assets_parent ON assets(parent_guid);";
+        indexCmd.ExecuteNonQuery();
+    }
+
+    private void TryAddColumn(string tableName, string columnName, string columnType)
+    {
+        try
+        {
+            using var cmd = _connection.CreateCommand();
+            cmd.CommandText = $"ALTER TABLE {tableName} ADD COLUMN {columnName} {columnType};";
+            cmd.ExecuteNonQuery();
+        }
+        catch (SqliteException)
+        {
+        }
     }
 
     private static string ToUniversalPath(string path)
@@ -147,6 +184,30 @@ public sealed partial class AssetCatalog : IDisposable
             _cmdUpsert.Parameters.AddWithValue("@content_hash", meta.ContentHash ?? (object)DBNull.Value);
             _cmdUpsert.Parameters.AddWithValue("@settings_hash", meta.SettingsHash ?? (object)DBNull.Value);
             _cmdUpsert.Parameters.AddWithValue("@imported_at_ms", meta.LastImportedUtc?.Ticks ?? (object)DBNull.Value);
+            _cmdUpsert.Parameters.AddWithValue("@parent_guid", DBNull.Value);
+            _cmdUpsert.Parameters.AddWithValue("@subasset_kind", DBNull.Value);
+            _cmdUpsert.Parameters.AddWithValue("@display_name", DBNull.Value);
+            _cmdUpsert.Parameters.AddWithValue("@stable_path", DBNull.Value);
+            _cmdUpsert.ExecuteNonQuery();
+        }
+    }
+
+    public void UpsertSubAsset(Guid parentGuid, AssetMeta meta, string sourcePath, string kind, string displayName, string stablePath)
+    {
+        lock (_writeLock)
+        {
+            _cmdUpsert.Parameters.Clear();
+            _cmdUpsert.Parameters.AddWithValue("@guid", meta.Guid.ToByteArray());
+            _cmdUpsert.Parameters.AddWithValue("@path", ToUniversalPath(sourcePath));
+            _cmdUpsert.Parameters.AddWithValue("@handler_id", meta.HandlerTypeId?.ToByteArray() ?? (object)DBNull.Value);
+            _cmdUpsert.Parameters.AddWithValue("@version", meta.HandlerVersion);
+            _cmdUpsert.Parameters.AddWithValue("@content_hash", meta.ContentHash ?? (object)DBNull.Value);
+            _cmdUpsert.Parameters.AddWithValue("@settings_hash", meta.SettingsHash ?? (object)DBNull.Value);
+            _cmdUpsert.Parameters.AddWithValue("@imported_at_ms", meta.LastImportedUtc?.Ticks ?? (object)DBNull.Value);
+            _cmdUpsert.Parameters.AddWithValue("@parent_guid", parentGuid.ToByteArray());
+            _cmdUpsert.Parameters.AddWithValue("@subasset_kind", kind);
+            _cmdUpsert.Parameters.AddWithValue("@display_name", displayName);
+            _cmdUpsert.Parameters.AddWithValue("@stable_path", stablePath);
             _cmdUpsert.ExecuteNonQuery();
         }
     }
@@ -245,6 +306,58 @@ public sealed partial class AssetCatalog : IDisposable
         }
     }
 
+    public List<SubAssetInfo> GetSubAssets(Guid parentGuid)
+    {
+        _cmdEnumerateSubAssets.Parameters.Clear();
+        _cmdEnumerateSubAssets.Parameters.AddWithValue("@parent_guid", parentGuid.ToByteArray());
+
+        using var reader = _cmdEnumerateSubAssets.ExecuteReader();
+        var list = new List<SubAssetInfo>();
+        while (reader.Read())
+        {
+            list.Add(new SubAssetInfo(
+                new Guid((byte[])reader[0]),
+                new Guid((byte[])reader[1]),
+                reader.GetString(2),
+                reader.GetString(3),
+                reader.GetString(4),
+                reader.GetString(5),
+                new Guid((byte[])reader[6])));
+        }
+
+        return list;
+    }
+
+    public void RemoveSubAssetsExcept(Guid parentGuid, ReadOnlySpan<Guid> keepGuids)
+    {
+        lock (_writeLock)
+        {
+            if (keepGuids.Length == 0)
+            {
+                _cmdDeleteSubAssetsForParent.Parameters.Clear();
+                _cmdDeleteSubAssetsForParent.Parameters.AddWithValue("@parent_guid", parentGuid.ToByteArray());
+                _cmdDeleteSubAssetsForParent.ExecuteNonQuery();
+                return;
+            }
+
+            var keep = new HashSet<Guid>();
+            for (var i = 0; i < keepGuids.Length; i++)
+            {
+                keep.Add(keepGuids[i]);
+            }
+
+            foreach (var subAsset in GetSubAssets(parentGuid))
+            {
+                if (!keep.Contains(subAsset.Guid))
+                {
+                    _cmdDelete.Parameters.Clear();
+                    _cmdDelete.Parameters.AddWithValue("@guid", subAsset.Guid.ToByteArray());
+                    _cmdDelete.ExecuteNonQuery();
+                }
+            }
+        }
+    }
+
     public void Dispose()
     {
         _cmdGetGuid.Dispose();
@@ -257,6 +370,8 @@ public sealed partial class AssetCatalog : IDisposable
         _cmdInsertDep.Dispose();
         _cmdClearDeps.Dispose();
         _cmdEnumerate.Dispose();
+        _cmdEnumerateSubAssets.Dispose();
+        _cmdDeleteSubAssetsForParent.Dispose();
         _connection.Dispose();
     }
 }

src/Editor/Ghost.Editor.Core/Services/AssetRegistry.cs

@@ -81,6 +81,11 @@ internal sealed class AssetRegistry : IAssetRegistry, IDisposable
 
         foreach (var (guid, path) in _catalog.EnumerateAll())
         {
+            if (path.Contains('#', StringComparison.Ordinal))
+            {
+                continue;
+            }
+
             if (!foundGuids.Contains(guid))
             {
                 _catalog.Remove(guid);
@@ -130,51 +135,58 @@ internal sealed class AssetRegistry : IAssetRegistry, IDisposable
             return;
         }
 
-        var relativePath = Path.GetRelativePath(EditorApplication.ProjectPath, e.FullPath);
+        try
-        var fileExists = File.Exists(e.FullPath);
-
-        if (ext == AssetMetaIO.META_EXTENSION)
         {
-            if (fileExists)
+            var relativePath = Path.GetRelativePath(EditorApplication.ProjectPath, e.FullPath);
+            var fileExists = File.Exists(e.FullPath);
+
+            if (ext == AssetMetaIO.META_EXTENSION)
             {
-                var meta = await AssetMetaIO.ReadAsync(e.FullPath);
+                if (fileExists)
-                if (meta != null)
                 {
-                    _catalog.Upsert(meta, AssetMetaIO.GetSourcePath(relativePath));
+                    var meta = await AssetMetaIO.ReadAsync(e.FullPath);
-                    await _importCoordinator.EnqueueAsync(new ImportJob(meta.Guid, AssetMetaIO.GetSourcePath(relativePath), relativePath, ImportReason.SettingsChanged));
+                    if (meta != null)
+                    {
+                        _catalog.Upsert(meta, AssetMetaIO.GetSourcePath(relativePath));
+                        await _importCoordinator.EnqueueAsync(new ImportJob(meta.Guid, AssetMetaIO.GetSourcePath(relativePath), relativePath, ImportReason.SettingsChanged));
+                    }
+                }
+                return;
+            }
+
+            var changeType = AssetChangeType.None;
+            var guid = _catalog.GetGuid(relativePath);
+
+            if (!fileExists)
+            {
+                // The file is no longer on disk. Wait safely completed.
+                if (guid != Guid.Empty)
+                {
+                    _catalog.Remove(guid);
+                    changeType = AssetChangeType.Deleted;
                 }
             }
-            return;
+            else if (guid == Guid.Empty)
-        }
-
-        var changeType = AssetChangeType.None;
-        var guid = _catalog.GetGuid(relativePath);
-
-        if (!fileExists)
-        {
-            // The file is no longer on disk. Wait safely completed.
-            if (guid != Guid.Empty)
             {
-                _catalog.Remove(guid);
+                // The file exists but isn't located inside our catalog yet -> Essentially a Creation
-                changeType = AssetChangeType.Deleted;
+                await HandleNewSourceFileAsync(relativePath);
+                changeType = AssetChangeType.Created;
+            }
+            else
+            {
+                // The file exists and is tracked in the catalog, but triggered an event -> Modification
+                await _importCoordinator.EnqueueAsync(new ImportJob(guid, relativePath, AssetMetaIO.GetMetaPath(relativePath), ImportReason.SourceChanged));
+                changeType = AssetChangeType.Modified;
+            }
+
+            if (changeType != AssetChangeType.None)
+            {
+                OnAssetChanged?.Invoke(this, new AssetChangedEventArgs(relativePath, null, changeType));
             }
         }
-        else if (guid == Guid.Empty)
+        catch (Exception ex)
         {
-            // The file exists but isn't located inside our catalog yet -> Essentially a Creation
+            Logger.Error(ex);
-            await HandleNewSourceFileAsync(relativePath);
-            changeType = AssetChangeType.Created;
-        }
-        else
-        {
-            // The file exists and is tracked in the catalog, but triggered an event -> Modification
-            await _importCoordinator.EnqueueAsync(new ImportJob(guid, relativePath, AssetMetaIO.GetMetaPath(relativePath), ImportReason.SourceChanged));
-            changeType = AssetChangeType.Modified;
-        }
-
-        if (changeType != AssetChangeType.None)
-        {
-            OnAssetChanged?.Invoke(this, new AssetChangedEventArgs(relativePath, null, changeType));
         }
     }
 

src/Editor/Ghost.Editor.Core/Services/ImportCoordinator.cs

@@ -112,10 +112,23 @@ internal sealed partial class ImportCoordinator : IDisposable
         }
 
         var importResult = Result.Success();
+        ImportedSubAsset[] subAssets = Array.Empty<ImportedSubAsset>();
         if (handler is IImportableAssetHandler importable)
         {
             var targetPath = GetImportedAssetPath(job.AssetGuid);
-            importResult = await importable.ImportAsync(job.SourcePath, targetPath, job.AssetGuid, meta.Settings, token);
+            if (importable is ISubAssetImportableAssetHandler subAssetImportable)
+            {
+                var subAssetResult = await subAssetImportable.ImportWithSubAssetsAsync(job.SourcePath, targetPath, job.AssetGuid, meta.Settings, token);
+                importResult = subAssetResult;
+                if (subAssetResult.IsSuccess)
+                {
+                    subAssets = subAssetResult.Value;
+                }
+            }
+            else
+            {
+                importResult = await importable.ImportAsync(job.SourcePath, targetPath, job.AssetGuid, meta.Settings, token);
+            }
         }
 
         if (importResult.IsSuccess)
@@ -127,6 +140,36 @@ internal sealed partial class ImportCoordinator : IDisposable
 
             await AssetMetaIO.WriteAsync(job.MetaPath, meta, token);
 
+            if (subAssets.Length > 0)
+            {
+                var dependencies = new Guid[subAssets.Length];
+                for (var i = 0; i < subAssets.Length; i++)
+                {
+                    var subAsset = subAssets[i];
+                    dependencies[i] = subAsset.Guid;
+
+                    var subMeta = new AssetMeta
+                    {
+                        Guid = subAsset.Guid,
+                        HandlerTypeId = subAsset.HandlerTypeId,
+                        HandlerVersion = meta.HandlerVersion,
+                        ContentHash = contentHash,
+                        SettingsHash = settingsHash,
+                        LastImportedUtc = meta.LastImportedUtc,
+                    };
+
+                    _catalog.UpsertSubAsset(job.AssetGuid, subMeta, subAsset.VirtualSourcePath, subAsset.Kind, subAsset.DisplayName, subAsset.StablePath);
+                }
+
+                _catalog.RemoveSubAssetsExcept(job.AssetGuid, dependencies);
+                _catalog.SetDependencies(job.AssetGuid, dependencies);
+            }
+            else if (handler is ISubAssetImportableAssetHandler)
+            {
+                _catalog.RemoveSubAssetsExcept(job.AssetGuid, ReadOnlySpan<Guid>.Empty);
+                _catalog.SetDependencies(job.AssetGuid, ReadOnlySpan<Guid>.Empty);
+            }
+
             OnImportCompleted?.Invoke(null, job.AssetGuid);
         }
         else

src/Runtime/Ghost.Core/Ghost.Core.csproj

@@ -8,7 +8,7 @@
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">
-    <DefineConstants>$(DefineConstants);MHP_ENABLE_SAFETY_CHECKS;MHP_ENABLE_MIMALLOC;MHP_FASTMATH</DefineConstants>
+    <DefineConstants>$(DefineConstants);MHP_ENABLE_SAFETY_CHECKS;MHP_ENABLE_MIMALLOC;MHP_FASTMATH;MHP_ENABLE_STACKTRACE</DefineConstants>
     <IsAotCompatible>True</IsAotCompatible>
     <IsTrimmable>True</IsTrimmable>
   </PropertyGroup>

src/Runtime/Ghost.Engine/AssetManager.Mesh.cs

@@ -0,0 +1,286 @@
+using Ghost.Core;
+using Ghost.Graphics;
+using Ghost.Graphics.Core;
+using Ghost.Graphics.RHI;
+using Ghost.Graphics.Utilities;
+using Misaki.HighPerformance.Mathematics.Geometry;
+using System.Runtime.CompilerServices;
+
+namespace Ghost.Engine;
+
+internal unsafe partial class AssetEntry
+{
+    private sealed unsafe class MeshParsedData
+    {
+        public MeshContentHeader header;
+        public byte* pVertices;
+        public byte* pIndices;
+        public byte* pMeshlets;
+        public byte* pMeshletGroups;
+        public byte* pMeshletHierarchyNodes;
+        public byte* pMeshletVertices;
+        public byte* pMeshletTriangles;
+    }
+
+    private static void RegisterMeshCallback()
+    {
+        s_onCreation[(int)AssetType.Mesh] = static (e) =>
+        {
+            var handle = e._resourceManager.CreateEmptyMesh();
+            e.SetStorage(handle);
+        };
+
+        s_onParseRawData[(int)AssetType.Mesh] = static (e) => e.ParseMeshData();
+        s_onRecordUpload[(int)AssetType.Mesh] = static (e, ctx) => e.RecordMeshUpload(ctx);
+        s_onUploadComplete[(int)AssetType.Mesh] = static (e, ctx) => e.OnMeshUploadComplete(ctx);
+        s_onReleaseResource[(int)AssetType.Mesh] = static (e) =>
+        {
+            var handle = e.GetStorage<Handle<Mesh>>();
+            if (handle.IsValid)
+            {
+                e._resourceManager.ReleaseMesh(handle);
+            }
+        };
+    }
+
+    private Result ParseMeshData()
+    {
+        var pData = (byte*)_rawData.GetUnsafePtr();
+        Logger.DebugAssert(pData != null);
+
+        if (_rawData.Size < (nuint)sizeof(MeshContentHeader))
+        {
+            return Result.Failure("Mesh content is smaller than the header.");
+        }
+
+        var header = Unsafe.ReadUnaligned<MeshContentHeader>(pData);
+        if (header.magic != MeshContentHeader.MAGIC || header.version != MeshContentHeader.VERSION)
+        {
+            return Result.Failure("Unsupported mesh content format.");
+        }
+
+        if (header.vertexCount == 0 || header.indexCount == 0 ||
+            header.meshletCount == 0 || header.meshletGroupCount == 0 ||
+            header.meshletHierarchyNodeCount == 0 || header.meshletVertexCount == 0 ||
+            header.meshletTriangleCount == 0)
+        {
+            return Result.Failure("Mesh content is missing required geometry or meshlet data.");
+        }
+
+        if (!ValidateRange(header.vertexOffset, header.vertexCount, (uint)sizeof(Vertex)) ||
+            !ValidateRange(header.indexOffset, header.indexCount, sizeof(uint)) ||
+            !ValidateRange(header.meshletOffset, header.meshletCount, (uint)sizeof(Meshlet)) ||
+            !ValidateRange(header.meshletGroupOffset, header.meshletGroupCount, (uint)sizeof(MeshletGroup)) ||
+            !ValidateRange(header.meshletHierarchyNodeOffset, header.meshletHierarchyNodeCount, (uint)sizeof(MeshletHierarchyNode)) ||
+            !ValidateRange(header.meshletVertexOffset, header.meshletVertexCount, sizeof(uint)) ||
+            !ValidateRange(header.meshletTriangleOffset, header.meshletTriangleCount, sizeof(uint)))
+        {
+            return Result.Failure("Mesh content contains an invalid data range.");
+        }
+
+        if (header.materialPartCount > 0 && !ValidateRange(header.materialPartOffset, header.materialPartCount, (uint)sizeof(MeshContentMaterialPart)))
+        {
+            return Result.Failure("Mesh content contains an invalid material part range.");
+        }
+
+        _parsedObject = new MeshParsedData
+        {
+            header = header,
+            pVertices = pData + header.vertexOffset,
+            pIndices = pData + header.indexOffset,
+            pMeshlets = pData + header.meshletOffset,
+            pMeshletGroups = pData + header.meshletGroupOffset,
+            pMeshletHierarchyNodes = pData + header.meshletHierarchyNodeOffset,
+            pMeshletVertices = pData + header.meshletVertexOffset,
+            pMeshletTriangles = pData + header.meshletTriangleOffset,
+        };
+
+        return Result.Success();
+
+        bool ValidateRange(ulong offset, uint count, uint stride)
+        {
+            var size = (ulong)count * stride;
+            return offset <= _rawData.Size && size <= _rawData.Size - (nuint)offset;
+        }
+    }
+
+    private Result RecordMeshUpload(ResourceStreamingContext context)
+    {
+        if (_parsedObject is not MeshParsedData data)
+        {
+            return Result.Failure("Mesh parse data is missing.");
+        }
+
+        ref readonly var header = ref data.header;
+
+        var vertexBuffer = CreateBuffer(context, data.pVertices, header.vertexCount, (uint)sizeof(Vertex),
+            BufferUsage.Vertex | BufferUsage.ShaderResource | BufferUsage.Raw, "Mesh_VertexBuffer");
+        var indexBuffer = CreateBuffer(context, data.pIndices, header.indexCount, sizeof(uint),
+            BufferUsage.Index | BufferUsage.ShaderResource | BufferUsage.Raw, "Mesh_IndexBuffer");
+        var meshletBuffer = CreateBuffer(context, data.pMeshlets, header.meshletCount, (uint)sizeof(Meshlet),
+            BufferUsage.Raw | BufferUsage.ShaderResource, "Mesh_Meshlets");
+        var meshletVerticesBuffer = CreateBuffer(context, data.pMeshletVertices, header.meshletVertexCount, sizeof(uint),
+            BufferUsage.Raw | BufferUsage.ShaderResource, "Mesh_MeshletVertices");
+        var meshletTrianglesBuffer = CreateBuffer(context, data.pMeshletTriangles, header.meshletTriangleCount, sizeof(uint),
+            BufferUsage.Raw | BufferUsage.ShaderResource, "Mesh_MeshletTriangles");
+        var meshletGroupBuffer = CreateBuffer(context, data.pMeshletGroups, header.meshletGroupCount, (uint)sizeof(MeshletGroup),
+            BufferUsage.Raw | BufferUsage.ShaderResource, "Mesh_MeshletGroups");
+        var meshletHierarchyBuffer = CreateBuffer(context, data.pMeshletHierarchyNodes, header.meshletHierarchyNodeCount, (uint)sizeof(MeshletHierarchyNode),
+            BufferUsage.Raw | BufferUsage.ShaderResource, "Mesh_MeshletHierarchy");
+
+        if (vertexBuffer.IsInvalid || indexBuffer.IsInvalid || meshletBuffer.IsInvalid ||
+            meshletVerticesBuffer.IsInvalid || meshletTrianglesBuffer.IsInvalid ||
+            meshletGroupBuffer.IsInvalid || meshletHierarchyBuffer.IsInvalid)
+        {
+            return Result.Failure("Failed to create one or more mesh GPU buffers.");
+        }
+
+        var meshData = new MeshData
+        {
+            worldBoundsMin = header.boundsMin,
+            worldBoundsMax = header.boundsMax,
+            vertexBuffer = context.ResourceDatabase.GetBindlessIndex(vertexBuffer.AsResource()),
+            indexBuffer = context.ResourceDatabase.GetBindlessIndex(indexBuffer.AsResource()),
+            meshletBuffer = context.ResourceDatabase.GetBindlessIndex(meshletBuffer.AsResource()),
+            meshletVerticesBuffer = context.ResourceDatabase.GetBindlessIndex(meshletVerticesBuffer.AsResource()),
+            meshletTrianglesBuffer = context.ResourceDatabase.GetBindlessIndex(meshletTrianglesBuffer.AsResource()),
+            meshletGroupBuffer = context.ResourceDatabase.GetBindlessIndex(meshletGroupBuffer.AsResource()),
+            meshletHierarchyBuffer = context.ResourceDatabase.GetBindlessIndex(meshletHierarchyBuffer.AsResource()),
+            meshletCount = header.meshletCount,
+            lodLevelCount = header.lodLevelCount,
+            materialSlotCount = header.materialSlotCount,
+        };
+
+        var meshDataBufferDesc = new BufferDesc
+        {
+            Size = (ulong)sizeof(MeshData),
+            Stride = (uint)sizeof(MeshData),
+            Usage = BufferUsage.Raw | BufferUsage.ShaderResource,
+            HeapType = HeapType.Default,
+        };
+
+        var meshDataBuffer = RenderingUtility.CreateBuffer(
+            context.ResourceManager,
+            context.ResourceDatabase,
+            context.ResourceAllocator,
+            context.CopyPipeline.GetCommandBuffer(),
+            &meshData,
+            (nuint)sizeof(MeshData),
+            in meshDataBufferDesc,
+            "Mesh_MeshDataBuffer");
+
+        if (meshDataBuffer.IsInvalid)
+        {
+            return Result.Failure("Failed to create mesh data buffer.");
+        }
+
+        var newHandle = context.ResourceManager.CreateUploadedMesh(
+            vertexBuffer,
+            indexBuffer,
+            meshletBuffer,
+            meshletVerticesBuffer,
+            meshletTrianglesBuffer,
+            meshletGroupBuffer,
+            meshletHierarchyBuffer,
+            meshDataBuffer,
+            (int)header.vertexCount,
+            (int)header.indexCount,
+            (int)header.meshletCount,
+            (int)header.lodLevelCount,
+            (int)header.materialSlotCount,
+            new AABB(header.boundsMin, header.boundsMax));
+
+        if (newHandle.IsInvalid)
+        {
+            return Result.Failure("Failed to register uploaded mesh.");
+        }
+
+        var oldHandle = GetStorage<Handle<Mesh>>();
+        SetStorage((oldHandle, newHandle));
+
+        return Result.Success();
+    }
+
+    private static Handle<GPUBuffer> CreateBuffer(ResourceStreamingContext context, void* pData, uint count, uint stride, BufferUsage usage, string name)
+    {
+        var desc = new BufferDesc
+        {
+            Size = (ulong)count * stride,
+            Stride = stride,
+            Usage = usage,
+            HeapType = HeapType.Default,
+        };
+
+        return RenderingUtility.CreateBuffer(
+            context.ResourceManager,
+            context.ResourceDatabase,
+            context.ResourceAllocator,
+            context.CopyPipeline.GetCommandBuffer(),
+            pData,
+            (nuint)desc.Size,
+            in desc,
+            name);
+    }
+
+    private void OnMeshUploadComplete(ResourceStreamingContext context)
+    {
+        var (oldHandle, newHandle) = GetStorage<(Handle<Mesh>, Handle<Mesh>)>();
+        var actualHandle = context.ResourceManager.ReplaceMesh(oldHandle, newHandle);
+        if (actualHandle.IsInvalid)
+        {
+            SetStorage(oldHandle);
+            return;
+        }
+
+        var result = context.ResourceManager.GetMeshReference(actualHandle);
+        if (result.IsSuccess)
+        {
+            ref readonly var mesh = ref result.Value;
+            context.GraphicsCommandBuffer.Barrier(
+                BarrierDesc.Buffer(mesh.VertexBuffer.AsResource(), BarrierSync.VertexShading, BarrierAccess.VertexBuffer | BarrierAccess.ShaderResource),
+                BarrierDesc.Buffer(mesh.IndexBuffer.AsResource(), BarrierSync.IndexInput, BarrierAccess.IndexBuffer | BarrierAccess.ShaderResource),
+                BarrierDesc.Buffer(mesh.MeshLetBuffer.AsResource(), BarrierSync.AllShading, BarrierAccess.ShaderResource),
+                BarrierDesc.Buffer(mesh.MeshletVerticesBuffer.AsResource(), BarrierSync.AllShading, BarrierAccess.ShaderResource),
+                BarrierDesc.Buffer(mesh.MeshletTrianglesBuffer.AsResource(), BarrierSync.AllShading, BarrierAccess.ShaderResource),
+                BarrierDesc.Buffer(mesh.MeshletGroupBuffer.AsResource(), BarrierSync.AllShading, BarrierAccess.ShaderResource),
+                BarrierDesc.Buffer(mesh.MeshletHierarchyBuffer.AsResource(), BarrierSync.AllShading, BarrierAccess.ShaderResource),
+                BarrierDesc.Buffer(mesh.MeshDataBuffer.AsResource(), BarrierSync.AllShading, BarrierAccess.ShaderResource));
+        }
+
+        SetStorage(actualHandle);
+
+        _rawData.Dispose();
+        _parsedObject = null;
+    }
+}
+
+internal partial class AssetManager
+{
+    public Handle<Mesh> ResolveMesh(Guid assetID)
+    {
+        if (assetID == Guid.Empty)
+        {
+            return Handle<Mesh>.Invalid;
+        }
+
+        var entry = GetOrCreateEntry(assetID);
+        Logger.DebugAssert(entry.AssetType == AssetType.Mesh);
+
+        return entry.GetStorage<Handle<Mesh>>();
+    }
+
+    public int ReleaseMesh(Guid assetID)
+    {
+        if (assetID == Guid.Empty)
+        {
+            return 0;
+        }
+
+        if (!_entries.TryGetValue(assetID, out var entry) || entry.AssetType != AssetType.Mesh)
+        {
+            return 0;
+        }
+
+        return entry.Release();
+    }
+}

src/Runtime/Ghost.Engine/AssetManager.cs

@@ -1,6 +1,7 @@
 using Ghost.Core;
 using Ghost.Core.Utilities;
 using Ghost.Graphics;
+using Ghost.Graphics.Services;
 using Ghost.Graphics.RHI;
 using Misaki.HighPerformance.Jobs;
 using Misaki.HighPerformance.LowLevel;
@@ -60,6 +61,7 @@ internal partial class AssetEntry
     static AssetEntry()
     {
         RegisterTextureCallback();
+        RegisterMeshCallback();
     }
 }
 
@@ -72,6 +74,7 @@ internal unsafe partial class AssetEntry
 
     private readonly AssetManager _assetManager;
     private readonly IResourceDatabase _resourceDatabase;
+    private readonly ResourceManager _resourceManager;
 
     private readonly Guid _assetId;
     private readonly AssetType _assetType;
@@ -101,10 +104,11 @@ internal unsafe partial class AssetEntry
         set => Volatile.Write(ref _state, (int)value);
     }
 
-    public AssetEntry(AssetManager manager, IResourceDatabase resourceDatabase, Guid assetId, AssetType assetType, Guid[] dependencies)
+    public AssetEntry(AssetManager manager, IResourceDatabase resourceDatabase, ResourceManager resourceManager, Guid assetId, AssetType assetType, Guid[] dependencies)
     {
         _assetManager = manager;
         _resourceDatabase = resourceDatabase;
+        _resourceManager = resourceManager;
 
         _assetId = assetId;
         _assetType = assetType;
@@ -288,6 +292,7 @@ internal struct LoadAssetJob : IJob
 internal partial class AssetManager : IDisposable
 {
     private readonly IResourceDatabase _resourceDatabase;
+    private readonly ResourceManager _resourceManager;
     private readonly IContentProvider _contentProvider;
     private readonly ResourceStreamingProcessor _streamingProcessor;
     private readonly JobScheduler _jobScheduler;
@@ -297,9 +302,10 @@ internal partial class AssetManager : IDisposable
     public IContentProvider ContentProvider => _contentProvider;
     public ResourceStreamingProcessor StreamingProcessor => _streamingProcessor;
 
-    internal AssetManager(IResourceDatabase resourceDatabase, IContentProvider contentProvider, ResourceStreamingProcessor streamingProcessor, JobScheduler jobScheduler)
+    internal AssetManager(IResourceDatabase resourceDatabase, ResourceManager resourceManager, IContentProvider contentProvider, ResourceStreamingProcessor streamingProcessor, JobScheduler jobScheduler)
     {
         _resourceDatabase = resourceDatabase;
+        _resourceManager = resourceManager;
         _contentProvider = contentProvider;
         _streamingProcessor = streamingProcessor;
         _jobScheduler = jobScheduler;
@@ -320,9 +326,13 @@ internal partial class AssetManager : IDisposable
 
     private void EnsureScheduled(AssetEntry entry)
     {
-        if (Interlocked.CompareExchange(ref entry.StateValue, (int)AssetState.Scheduled, (int)AssetState.Unloaded) != (int)AssetState.Unloaded)
+        var previousState = Interlocked.CompareExchange(ref entry.StateValue, (int)AssetState.Scheduled, (int)AssetState.Unloaded);
+        if (previousState != (int)AssetState.Unloaded)
         {
-            return;
+            if (previousState != (int)AssetState.Scheduled || entry.LoadJobHandle.IsValid)
+            {
+                return;
+            }
         }
 
         // TODO: Can this be jobified? If the dependency tree is not deep, it should be fine to do it in main thread, otherwise we might need to schedule a job to do it.
@@ -397,7 +407,7 @@ internal partial class AssetManager : IDisposable
             var type = self._contentProvider.GetAssetType(id);
             var deps = self._contentProvider.GetDependencies(id);
 
-            var entry = new AssetEntry(self, self._resourceDatabase, id, type, deps);
+            var entry = new AssetEntry(self, self._resourceDatabase, self._resourceManager, id, type, deps);
 
             self.EnsureScheduled(entry);
             return entry;
@@ -420,6 +430,7 @@ internal partial class AssetManager : IDisposable
             // Go directly to Scheduled -> Loading -> Loaded -> Uploading -> Ready again.
             // The swap cycle in RecordTextureUpload/OnTextureUploadComplete handles the 
             // v1 to v2 transition exactly like the fallback to v1 transition.
+            entry.SetLoadJobHandle(JobHandle.Invalid);
             EnsureScheduled(entry);
         }
         else

src/Runtime/Ghost.Engine/EngineCore.cs

@@ -47,7 +47,7 @@ public sealed partial class EngineCore : IDisposable
         };
 
         _renderSystem = new RenderSystem(renderingDesc);
-        _assetManager = new AssetManager(_renderSystem.GraphicsEngine.ResourceDatabase, _contentProvider, _streamingProcessor, _jobScheduler);
+        _assetManager = new AssetManager(_renderSystem.GraphicsEngine.ResourceDatabase, _renderSystem.ResourceManager, _contentProvider, _streamingProcessor, _jobScheduler);
     }
 
     public void Dispose()
@@ -56,4 +56,4 @@ public sealed partial class EngineCore : IDisposable
         _renderSystem.Dispose();
         _jobScheduler.Dispose();
     }
-}
+}

src/Runtime/Ghost.Engine/MeshContent.cs

@@ -0,0 +1,47 @@
+using Misaki.HighPerformance.Mathematics;
+using System.Runtime.InteropServices;
+
+namespace Ghost.Engine;
+
+[StructLayout(LayoutKind.Sequential)]
+public struct MeshContentHeader
+{
+    public const uint MAGIC = 0x48534D47; // GMSH
+    public const uint VERSION = 1;
+
+    public uint magic;
+    public uint version;
+
+    public uint vertexCount;
+    public uint indexCount;
+    public uint materialPartCount;
+    public uint meshletCount;
+    public uint meshletGroupCount;
+    public uint meshletHierarchyNodeCount;
+    public uint meshletVertexCount;
+    public uint meshletTriangleCount;
+    public uint materialSlotCount;
+    public uint lodLevelCount;
+
+    public float3 boundsMin;
+    public float3 boundsMax;
+
+    public ulong vertexOffset;
+    public ulong indexOffset;
+    public ulong materialPartOffset;
+    public ulong meshletOffset;
+    public ulong meshletGroupOffset;
+    public ulong meshletHierarchyNodeOffset;
+    public ulong meshletVertexOffset;
+    public ulong meshletTriangleOffset;
+}
+
+[StructLayout(LayoutKind.Sequential)]
+public struct MeshContentMaterialPart
+{
+    public int materialIndex;
+    public int indexStart;
+    public int indexCount;
+    public int vertexStart;
+    public int vertexCount;
+}

src/Runtime/Ghost.Generator/AssetHandlerRegistrationGenerator.cs

@@ -141,6 +141,11 @@ internal static partial class {registerTypeName}
             return null;
         }
 
+        if (symbol.IsAbstract)
+        {
+            return null;
+        }
+
         var iSettingsSymbol = context.SemanticModel.Compilation.GetTypeByMetadataName("Ghost.Editor.Core.Assets.IAssetSettings");
         if (iSettingsSymbol == null)
         {

src/Runtime/Ghost.Graphics.RHI/RootSignatureLayout.cs

@@ -70,5 +70,9 @@ public struct MeshData
     public uint meshletBuffer;
     public uint meshletVerticesBuffer;
     public uint meshletTrianglesBuffer;
+    public uint meshletGroupBuffer;
+    public uint meshletHierarchyBuffer;
+    public uint meshletCount;
+    public uint lodLevelCount;
     public uint materialSlotCount;     // number of material slots baked into this mesh's meshlets
 };

src/Runtime/Ghost.Graphics/Core/Mesh.cs

@@ -185,6 +185,22 @@ public struct Mesh : IResourceReleasable
         get; internal set;
     }
 
+    /// <summary>
+    /// Gets the handle to the meshlet group buffer on the GPU.
+    /// </summary>
+    public Handle<GPUBuffer> MeshletGroupBuffer
+    {
+        get; internal set;
+    }
+
+    /// <summary>
+    /// Gets the handle to the meshlet hierarchy buffer on the GPU.
+    /// </summary>
+    public Handle<GPUBuffer> MeshletHierarchyBuffer
+    {
+        get; internal set;
+    }
+
     /// <summary>
     /// Gets the handle to the mesh data buffer on the GPU.
     /// </summary>
@@ -193,6 +209,19 @@ public struct Mesh : IResourceReleasable
         get; internal set;
     }
 
+    internal void SetMeshletSummary(int meshletCount, int lodLevelCount, int materialSlotCount)
+    {
+        _meshletData.meshletCount = meshletCount;
+        _meshletData.lodLevelCount = lodLevelCount;
+        _meshletData.materialSlotCount = materialSlotCount;
+    }
+
+    internal void SetCounts(int vertexCount, int indexCount)
+    {
+        VertexCount = vertexCount;
+        IndexCount = indexCount;
+    }
+
     public void ReleaseCpuResources()
     {
         _vertices.Dispose();
@@ -209,6 +238,8 @@ public struct Mesh : IResourceReleasable
         database.ReleaseResource(MeshLetBuffer.AsResource());
         database.ReleaseResource(MeshletVerticesBuffer.AsResource());
         database.ReleaseResource(MeshletTrianglesBuffer.AsResource());
+        database.ReleaseResource(MeshletGroupBuffer.AsResource());
+        database.ReleaseResource(MeshletHierarchyBuffer.AsResource());
         database.ReleaseResource(MeshDataBuffer.AsResource());
     }
 }

src/Runtime/Ghost.Graphics/Core/RenderContext.cs

@@ -254,22 +254,44 @@ public readonly unsafe ref struct RenderContext
             Usage = BufferUsage.Raw | BufferUsage.ShaderResource,
             HeapType = HeapType.Default,
         };
+        var groupsDesc = new BufferDesc
+        {
+            Size = (uint)(meshletData.groups.Count * sizeof(MeshletGroup)),
+            Stride = (uint)sizeof(MeshletGroup),
+            Usage = BufferUsage.Raw | BufferUsage.ShaderResource,
+            HeapType = HeapType.Default,
+        };
+        var hierarchyDesc = new BufferDesc
+        {
+            Size = (uint)(meshletData.hierarchyNodes.Count * sizeof(MeshletHierarchyNode)),
+            Stride = (uint)sizeof(MeshletHierarchyNode),
+            Usage = BufferUsage.Raw | BufferUsage.ShaderResource,
+            HeapType = HeapType.Default,
+        };
 
         meshRef.MeshLetBuffer = ResourceAllocator.CreateBuffer(in meshletDesc, "Meshlets");
         meshRef.MeshletVerticesBuffer = ResourceAllocator.CreateBuffer(in verticesDesc, "MeshletVertices");
         meshRef.MeshletTrianglesBuffer = ResourceAllocator.CreateBuffer(in trianglesDesc, "MeshletTriangles");
+        meshRef.MeshletGroupBuffer = ResourceAllocator.CreateBuffer(in groupsDesc, "MeshletGroups");
+        meshRef.MeshletHierarchyBuffer = ResourceAllocator.CreateBuffer(in hierarchyDesc, "MeshletHierarchy");
 
         TransitionBarrier(meshRef.MeshLetBuffer.AsResource(), false, BarrierLayout.Undefined, BarrierAccess.CopyDest, BarrierSync.Copy);
         TransitionBarrier(meshRef.MeshletVerticesBuffer.AsResource(), false, BarrierLayout.Undefined, BarrierAccess.CopyDest, BarrierSync.Copy);
         TransitionBarrier(meshRef.MeshletTrianglesBuffer.AsResource(), false, BarrierLayout.Undefined, BarrierAccess.CopyDest, BarrierSync.Copy);
+        TransitionBarrier(meshRef.MeshletGroupBuffer.AsResource(), false, BarrierLayout.Undefined, BarrierAccess.CopyDest, BarrierSync.Copy);
+        TransitionBarrier(meshRef.MeshletHierarchyBuffer.AsResource(), false, BarrierLayout.Undefined, BarrierAccess.CopyDest, BarrierSync.Copy);
 
         UploadBuffer(meshRef.MeshLetBuffer, meshletData.meshlets.AsSpan());
         UploadBuffer(meshRef.MeshletVerticesBuffer, meshletData.meshletVertices.AsSpan());
         UploadBuffer(meshRef.MeshletTrianglesBuffer, meshletData.meshletTriangles.AsSpan());
+        UploadBuffer(meshRef.MeshletGroupBuffer, meshletData.groups.AsSpan());
+        UploadBuffer(meshRef.MeshletHierarchyBuffer, meshletData.hierarchyNodes.AsSpan());
 
         TransitionBarrier(meshRef.MeshLetBuffer.AsResource(), false, BarrierLayout.Undefined, BarrierAccess.ShaderResource, BarrierSync.NonPixelShading | BarrierSync.PixelShading);
         TransitionBarrier(meshRef.MeshletVerticesBuffer.AsResource(), false, BarrierLayout.Undefined, BarrierAccess.ShaderResource, BarrierSync.NonPixelShading | BarrierSync.PixelShading);
         TransitionBarrier(meshRef.MeshletTrianglesBuffer.AsResource(), false, BarrierLayout.Undefined, BarrierAccess.ShaderResource, BarrierSync.NonPixelShading | BarrierSync.PixelShading);
+        TransitionBarrier(meshRef.MeshletGroupBuffer.AsResource(), false, BarrierLayout.Undefined, BarrierAccess.ShaderResource, BarrierSync.NonPixelShading | BarrierSync.PixelShading);
+        TransitionBarrier(meshRef.MeshletHierarchyBuffer.AsResource(), false, BarrierLayout.Undefined, BarrierAccess.ShaderResource, BarrierSync.NonPixelShading | BarrierSync.PixelShading);
     }
 
     public void UpdateObjectData(Handle<Mesh> mesh)
@@ -290,6 +312,10 @@ public readonly unsafe ref struct RenderContext
             meshletBuffer = ResourceDatabase.GetBindlessIndex(meshData.MeshLetBuffer.AsResource()),
             meshletVerticesBuffer = ResourceDatabase.GetBindlessIndex(meshData.MeshletVerticesBuffer.AsResource()),
             meshletTrianglesBuffer = ResourceDatabase.GetBindlessIndex(meshData.MeshletTrianglesBuffer.AsResource()),
+            meshletGroupBuffer = ResourceDatabase.GetBindlessIndex(meshData.MeshletGroupBuffer.AsResource()),
+            meshletHierarchyBuffer = ResourceDatabase.GetBindlessIndex(meshData.MeshletHierarchyBuffer.AsResource()),
+            meshletCount = (uint)meshData.MeshletData.meshletCount,
+            lodLevelCount = (uint)meshData.MeshletData.lodLevelCount,
             materialSlotCount = (uint)meshData.MeshletData.materialSlotCount,
         };
 

src/Runtime/Ghost.Graphics/Services/ResourceManager.cs

@@ -4,6 +4,7 @@ using Ghost.Graphics.Core;
 using Ghost.Graphics.RHI;
 using Misaki.HighPerformance.LowLevel.Buffer;
 using Misaki.HighPerformance.LowLevel.Collections;
+using Misaki.HighPerformance.Mathematics.Geometry;
 
 namespace Ghost.Graphics.Services;
 
@@ -165,6 +166,79 @@ public sealed partial class ResourceManager : IDisposable
         }
     }
 
+    public Handle<Mesh> CreateEmptyMesh(string? name = null)
+    {
+        Logger.DebugAssert(!_disposed);
+
+        lock (_meshWriteLock)
+        {
+            var id = _meshes.Add(new Mesh(), out var generation);
+            return new Handle<Mesh>(id, generation);
+        }
+    }
+
+    public Handle<Mesh> CreateUploadedMesh(
+        Handle<GPUBuffer> vertexBuffer,
+        Handle<GPUBuffer> indexBuffer,
+        Handle<GPUBuffer> meshletBuffer,
+        Handle<GPUBuffer> meshletVerticesBuffer,
+        Handle<GPUBuffer> meshletTrianglesBuffer,
+        Handle<GPUBuffer> meshletGroupBuffer,
+        Handle<GPUBuffer> meshletHierarchyBuffer,
+        Handle<GPUBuffer> meshDataBuffer,
+        int vertexCount,
+        int indexCount,
+        int meshletCount,
+        int lodLevelCount,
+        int materialSlotCount,
+        AABB boundingBox)
+    {
+        Logger.DebugAssert(!_disposed);
+
+        var mesh = new Mesh
+        {
+            VertexBuffer = vertexBuffer,
+            IndexBuffer = indexBuffer,
+            MeshLetBuffer = meshletBuffer,
+            MeshletVerticesBuffer = meshletVerticesBuffer,
+            MeshletTrianglesBuffer = meshletTrianglesBuffer,
+            MeshletGroupBuffer = meshletGroupBuffer,
+            MeshletHierarchyBuffer = meshletHierarchyBuffer,
+            MeshDataBuffer = meshDataBuffer,
+            BoundingBox = boundingBox,
+        };
+        mesh.SetCounts(vertexCount, indexCount);
+        mesh.SetMeshletSummary(meshletCount, lodLevelCount, materialSlotCount);
+
+        lock (_meshWriteLock)
+        {
+            var id = _meshes.Add(mesh, out var generation);
+            return new Handle<Mesh>(id, generation);
+        }
+    }
+
+    public Handle<Mesh> ReplaceMesh(Handle<Mesh> dst, Handle<Mesh> src)
+    {
+        Logger.DebugAssert(!_disposed);
+
+        lock (_meshWriteLock)
+        {
+            ref var dstMesh = ref _meshes.GetElementReferenceAt(dst.ID, dst.Generation, out var dstExists);
+            ref var srcMesh = ref _meshes.GetElementReferenceAt(src.ID, src.Generation, out var srcExists);
+            if (!dstExists || !srcExists)
+            {
+                return Handle<Mesh>.Invalid;
+            }
+
+            var oldMesh = dstMesh;
+            dstMesh = srcMesh;
+            _meshes.Remove(src.ID, src.Generation);
+
+            oldMesh.ReleaseResource(_resourceDatabase);
+            return dst;
+        }
+    }
+
     /// <summary>
     /// Creates a new material instance using the specified shader.
     /// </summary>

src/Runtime/Ghost.Graphics/Shaders/Includes/Properties.hlsl

@@ -61,6 +61,10 @@ struct MeshData
     BYTE_ADDRESS_BUFFER meshletBuffer;
     BYTE_ADDRESS_BUFFER meshletVerticesBuffer;
     BYTE_ADDRESS_BUFFER meshletTrianglesBuffer;
+    BYTE_ADDRESS_BUFFER meshletGroupBuffer;
+    BYTE_ADDRESS_BUFFER meshletHierarchyBuffer;
+    uint meshletCount;
+    uint lodLevelCount;
     uint materialSlotCount;
 };
 

src/Runtime/Ghost.Graphics/Utilities/MeshBuilder.cs

@@ -230,7 +230,7 @@ public static unsafe class MeshBuilder
     public static void ComputeTangents(Span<Vertex> vertices, Span<uint> indices)
     {
         using var scope = AllocationManager.CreateStackScope();
-        var bitangents = new UnsafeArray<float3>(vertices.Length, scope.AllocationHandle, AllocationOption.Clear);
+        using var bitangents = new UnsafeArray<float3>(vertices.Length, scope.AllocationHandle, AllocationOption.Clear);
 
         for (var i = 0; i < indices.Length; i += 3)
         {

src/Test/Ghost.MicroTest/Program.cs

@@ -1,4 +1,4 @@
 using Ghost.MicroTest;
 using Ghost.Test.Core;
 
-TestRunner.Run<NvttBindingTest>();
+TestRunner.Run<UfbxBindingTest>();

src/Test/Ghost.UnitTest/AssetSystem/AssertRegistryTest.cs

@@ -1,3 +1,4 @@
+using Ghost.Editor.Core;
 using Ghost.Editor.Core.Assets;
 using Ghost.Editor.Core.Contracts;
 using Ghost.Editor.Core.Services;
@@ -7,16 +8,21 @@ namespace Ghost.UnitTest.AssetSystem;
 [TestClass]
 public class AssertRegistryTest
 {
-    private string _assetsRoot = null!;
     private IAssetRegistry _registry = null!;
 
+    public TestContext TestContext
+    {
+        get; set;
+    }
+
     [TestInitialize]
     public void Setup()
     {
         var testDir = Path.Combine(Path.GetTempPath(), "GhostEngineTests", Guid.NewGuid().ToString());
         Directory.CreateDirectory(testDir);
-        
+
-        _assetsRoot = Path.Combine(testDir, "Assets");
+        EditorApplication.Initialize(null!, testDir, "Test");
+
         _registry = new AssetRegistry();
     }
 
@@ -29,16 +35,20 @@ public class AssertRegistryTest
     [TestMethod]
     public async Task TestAssetRegistry_AutoImport()
     {
-        var sourcePath = "test.text";
+        var sourcePath = "Assets/test.text";
-        var fullSourcePath = Path.Combine(_assetsRoot, sourcePath);
+        await File.WriteAllBytesAsync(sourcePath, [1, 2, 3], TestContext.CancellationToken);
-        await File.WriteAllBytesAsync(fullSourcePath, [1, 2, 3]);
-
-        await Task.Delay(1000); // Wait for FSW to trigger
         
-        var metaPath = AssetMetaIO.GetMetaPath(fullSourcePath);
+        var metaPath = AssetMetaIO.GetMetaPath(sourcePath);
+
+        using var cts = new CancellationTokenSource(5000);
+        while (!File.Exists(metaPath) && !cts.IsCancellationRequested)
+        {
+            await Task.Delay(50, cts.Token);
+        }
+
         Assert.IsTrue(File.Exists(metaPath));
         
-        var meta = await AssetMetaIO.ReadAsync(metaPath);
+        var meta = await AssetMetaIO.ReadAsync(metaPath, TestContext.CancellationToken);
         Assert.IsNotNull(meta);
 
         var guid = _registry.GetAssetGuid(sourcePath);

src/Test/Ghost.UnitTest/AssetSystem/AssetCatalogTests.cs

@@ -49,7 +49,7 @@ public class AssetCatalogTests
         catalog.Upsert(meta, path);
 
         Assert.AreEqual(guid, catalog.GetGuid(path));
-        Assert.AreEqual(path, catalog.GetSourcePath(guid));
+        Assert.AreEqual(Path.GetFullPath(path).Replace('\\', '/'), catalog.GetSourcePath(guid));
     }
 
     [TestMethod]
@@ -68,4 +68,35 @@ public class AssetCatalogTests
         Assert.AreEqual(1, referencers.Count);
         Assert.AreEqual(asset1, referencers[0]);
     }
+
+    [TestMethod]
+    public void TestAssetCatalog_VirtualSubAssets()
+    {
+        using var catalog = new AssetCatalog(_dbPath);
+        var parent = Guid.NewGuid();
+        var subMesh = Guid.NewGuid();
+        var handlerTypeId = Guid.NewGuid();
+
+        catalog.Upsert(new AssetMeta { Guid = parent, HandlerTypeId = handlerTypeId, HandlerVersion = 1 }, "Props/kit.fbx");
+        catalog.UpsertSubAsset(parent,
+            new AssetMeta { Guid = subMesh, HandlerTypeId = handlerTypeId, HandlerVersion = 1 },
+            "Props/kit.fbx#Mesh/Root/Crate",
+            "Mesh",
+            "Crate",
+            "Root/Crate");
+        catalog.SetDependencies(parent, stackalloc[] { subMesh });
+
+        Assert.AreEqual(subMesh, catalog.GetGuid("Props/kit.fbx#Mesh/Root/Crate"));
+        var subAssets = catalog.GetSubAssets(parent);
+        Assert.AreEqual(1, subAssets.Count);
+        Assert.AreEqual(subMesh, subAssets[0].Guid);
+        Assert.AreEqual(parent, subAssets[0].ParentGuid);
+        Assert.AreEqual("Mesh", subAssets[0].Kind);
+        Assert.AreEqual("Crate", subAssets[0].DisplayName);
+        Assert.AreEqual("Root/Crate", subAssets[0].StablePath);
+
+        var dependencies = catalog.GetDependencies(parent);
+        Assert.AreEqual(1, dependencies.Count);
+        Assert.AreEqual(subMesh, dependencies[0]);
+    }
 }

src/Test/Ghost.UnitTest/AssetSystem/AssetManagerTest.cs

@@ -50,7 +50,7 @@ public class AssetManagerTest
         };
         _jobScheduler = new JobScheduler(in schedulerDesc);
 
-        _assetManager = new AssetManager(_graphicsEngine.ResourceDatabase, _provider, _processor, _jobScheduler);
+        _assetManager = new AssetManager(_graphicsEngine.ResourceDatabase, _resourceManager, _provider, _processor, _jobScheduler);
     }
 
     [TestCleanup]
@@ -109,4 +109,89 @@ public class AssetManagerTest
         Assert.AreEqual(BarrierLayout.ShaderResource, data.layout);
         Assert.AreEqual(BarrierSync.AllShading, data.sync);
     }
+
+    [TestMethod]
+    public async Task AssetManager_ResolveMeshThenBackgroundUpload()
+    {
+        var assetID = Guid.NewGuid();
+        _provider.AddMockMesh(assetID, readDelayMs: Random.Shared.Next(10, 50));
+
+        var handle = _assetManager.ResolveMesh(assetID);
+        Assert.IsTrue(handle.IsValid);
+
+        Assert.IsTrue(_assetManager.TryGetEntry(assetID, out var entry));
+        Assert.IsGreaterThanOrEqualTo((int)AssetState.Scheduled, entry.StateValue);
+
+        await Task.Delay(1000, TestContext.CancellationToken);
+
+        Assert.IsGreaterThanOrEqualTo((int)AssetState.Loaded, entry.StateValue);
+
+        var ctx = new ResourceStreamingContext
+        {
+            ResourceManager = _resourceManager,
+            ResourceDatabase = _graphicsEngine.ResourceDatabase,
+            ResourceAllocator = _graphicsEngine.ResourceAllocator,
+            CopyPipeline = _copyPipeline,
+            GraphicsCommandBuffer = _commandBuffer,
+        };
+
+        _processor.ProcessPendingUploads(ctx);
+
+        await Task.Delay(1000, TestContext.CancellationToken);
+
+        Assert.IsGreaterThanOrEqualTo((int)AssetState.Uploading, entry.StateValue);
+
+        _processor.ProcessPendingUploads(ctx);
+
+        Assert.IsGreaterThanOrEqualTo((int)AssetState.Ready, entry.StateValue);
+        Assert.IsTrue(_resourceManager.HasMesh(handle));
+
+        ref readonly var mesh = ref _resourceManager.GetMeshReference(handle).GetValueOrThrow();
+        var (vertexBarrier, vertexError) = _graphicsEngine.ResourceDatabase.GetResourceBarrierData(mesh.VertexBuffer.AsResource());
+        var (indexBarrier, indexError) = _graphicsEngine.ResourceDatabase.GetResourceBarrierData(mesh.IndexBuffer.AsResource());
+        var (meshDataBarrier, meshDataError) = _graphicsEngine.ResourceDatabase.GetResourceBarrierData(mesh.MeshDataBuffer.AsResource());
+
+        Assert.AreEqual(Error.None, vertexError);
+        Assert.AreEqual(Error.None, indexError);
+        Assert.AreEqual(Error.None, meshDataError);
+        Assert.IsTrue(vertexBarrier.access.HasFlag(BarrierAccess.VertexBuffer));
+        Assert.IsTrue(indexBarrier.access.HasFlag(BarrierAccess.IndexBuffer));
+        Assert.AreEqual(BarrierAccess.ShaderResource, meshDataBarrier.access);
+    }
+
+    [TestMethod]
+    public async Task AssetManager_ReimportMeshKeepsStableHandle()
+    {
+        var assetID = Guid.NewGuid();
+        _provider.AddMockMesh(assetID);
+
+        var handle = _assetManager.ResolveMesh(assetID);
+        await Task.Delay(1000, TestContext.CancellationToken);
+
+        var ctx = new ResourceStreamingContext
+        {
+            ResourceManager = _resourceManager,
+            ResourceDatabase = _graphicsEngine.ResourceDatabase,
+            ResourceAllocator = _graphicsEngine.ResourceAllocator,
+            CopyPipeline = _copyPipeline,
+            GraphicsCommandBuffer = _commandBuffer,
+        };
+
+        _processor.ProcessPendingUploads(ctx);
+        _processor.ProcessPendingUploads(ctx);
+
+        Assert.IsTrue(_assetManager.TryGetEntry(assetID, out var entry));
+        Assert.AreEqual(AssetState.Ready, entry.State);
+
+        _provider.AddMockMesh(assetID);
+        _assetManager.ReimportAsset(assetID);
+        await Task.Delay(1000, TestContext.CancellationToken);
+
+        _processor.ProcessPendingUploads(ctx);
+        _processor.ProcessPendingUploads(ctx);
+
+        var reimportedHandle = _assetManager.ResolveMesh(assetID);
+        Assert.AreEqual(handle, reimportedHandle);
+        Assert.AreEqual(AssetState.Ready, entry.State);
+    }
 }

src/Test/Ghost.UnitTest/AssetSystem/MeshAssetHandlerTests.cs

@@ -0,0 +1,145 @@
+using Ghost.Core;
+using Ghost.Editor.Core;
+using Ghost.Editor.Core.Assets;
+using Ghost.Editor.Core.Services;
+using Ghost.Engine;
+using Misaki.HighPerformance.LowLevel.Buffer;
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace Ghost.UnitTest.AssetSystem;
+
+[TestClass]
+public class MeshAssetHandlerTests
+{
+    private sealed class EmptyServiceProvider : IServiceProvider
+    {
+        public object? GetService(Type serviceType)
+        {
+            return null;
+        }
+    }
+
+    private string _projectRoot = null!;
+    private string _previousCurrentDirectory = null!;
+
+    [TestInitialize]
+    public void Setup()
+    {
+        AllocationManager.Initialize(AllocationManagerDesc.Default);
+
+        _previousCurrentDirectory = Environment.CurrentDirectory;
+        _projectRoot = Path.Combine(Path.GetTempPath(), "GhostEngineTests", Guid.NewGuid().ToString());
+        Directory.CreateDirectory(_projectRoot);
+        EditorApplication.Initialize(new EmptyServiceProvider(), _projectRoot, "MeshImportTest");
+    }
+
+    [TestCleanup]
+    public void Cleanup()
+    {
+        AllocationManager.Dispose();
+        Environment.CurrentDirectory = _previousCurrentDirectory;
+
+        if (Directory.Exists(_projectRoot))
+        {
+            try
+            {
+                Directory.Delete(_projectRoot, true);
+            }
+            catch (IOException)
+            {
+                Thread.Sleep(100);
+                if (Directory.Exists(_projectRoot))
+                {
+                    Directory.Delete(_projectRoot, true);
+                }
+            }
+        }
+    }
+
+    [TestMethod]
+    public async Task FBXAssetHandler_ImportsObjAsManifestAndMeshSubAssets()
+    {
+        var sourcePath = Path.Combine(EditorApplication.AssetsFolderPath, "kit.obj");
+        await File.WriteAllTextAsync(sourcePath, CreateTwoObjectObj());
+
+        var parentGuid = Guid.NewGuid();
+        var targetPath = ImportCoordinator.GetImportedAssetPath(parentGuid);
+        var handler = new FBXAssetHandler();
+
+        var result = await handler.ImportWithSubAssetsAsync(sourcePath, targetPath, parentGuid, new ObjAssetSettings(), TestContext.CancellationToken);
+
+        if (result.IsFailure && result.Message?.Contains("Unable to load DLL", StringComparison.OrdinalIgnoreCase) == true)
+        {
+            Assert.Inconclusive(result.Message);
+        }
+
+        Assert.IsTrue(result.IsSuccess, result.Message);
+        Assert.IsTrue(File.Exists(targetPath));
+        Assert.IsGreaterThanOrEqualTo(result.Value.Length, 2);
+
+        foreach (var subAsset in result.Value)
+        {
+            Assert.AreEqual("Mesh", subAsset.Kind);
+            Assert.IsTrue(subAsset.VirtualSourcePath.Contains("#Mesh/", StringComparison.Ordinal));
+
+            var meshPath = ImportCoordinator.GetImportedAssetPath(subAsset.Guid);
+            Assert.IsTrue(File.Exists(meshPath));
+
+            await using var stream = new FileStream(meshPath, FileMode.Open, FileAccess.Read, FileShare.Read);
+            var headerBytes = new byte[Marshal.SizeOf<MeshContentHeader>()];
+            await stream.ReadExactlyAsync(headerBytes, TestContext.CancellationToken);
+
+            var header = MemoryMarshal.Read<MeshContentHeader>(headerBytes);
+            Assert.AreEqual(MeshContentHeader.MAGIC, header.magic);
+            Assert.AreEqual(MeshContentHeader.VERSION, header.version);
+            Assert.IsGreaterThan(0u, header.vertexCount);
+            Assert.IsGreaterThan(0u, header.indexCount);
+            Assert.IsGreaterThan(0u, header.meshletCount);
+            Assert.IsGreaterThan(0u, header.meshletGroupCount);
+            Assert.IsGreaterThan(0u, header.meshletHierarchyNodeCount);
+        }
+    }
+
+    public TestContext TestContext
+    {
+        get; set;
+    } = null!;
+
+    private static string CreateTwoObjectObj()
+    {
+        var sb = new StringBuilder();
+        AppendGrid(sb, "PropA", 0, 0);
+        AppendGrid(sb, "PropB", 49, 1);
+        return sb.ToString();
+    }
+
+    private static void AppendGrid(StringBuilder sb, string name, int vertexOffset, int z)
+    {
+        const int size = 6;
+        sb.AppendLine($"o {name}");
+
+        for (var y = 0; y <= size; y++)
+        {
+            for (var x = 0; x <= size; x++)
+            {
+                sb.AppendLine($"v {x} {y} {z}");
+                sb.AppendLine("vn 0 0 1");
+                sb.AppendLine($"vt {x / (float)size} {y / (float)size}");
+            }
+        }
+
+        for (var y = 0; y < size; y++)
+        {
+            for (var x = 0; x < size; x++)
+            {
+                var i0 = vertexOffset + y * (size + 1) + x + 1;
+                var i1 = i0 + 1;
+                var i2 = i0 + size + 1;
+                var i3 = i2 + 1;
+                sb.AppendLine($"f {i0}/{i0}/{i0} {i1}/{i1}/{i1} {i2}/{i2}/{i2}");
+                sb.AppendLine($"f {i1}/{i1}/{i1} {i3}/{i3}/{i3} {i2}/{i2}/{i2}");
+            }
+        }
+    }
+}

src/Test/Ghost.UnitTest/MockingEnvironment/MockingContentProvider.cs

@@ -1,6 +1,11 @@
 using Ghost.Core;
 using Ghost.Engine;
+using Ghost.Graphics.Core;
+using Ghost.Graphics.RHI;
+using Misaki.HighPerformance.Mathematics;
+using Misaki.HighPerformance.Mathematics.Geometry;
 using System.Collections.Concurrent;
+using System.Runtime.InteropServices;
 
 namespace Ghost.UnitTest.MockingEnvironment;
 
@@ -59,6 +64,118 @@ internal class MockingContentProvider : IContentProvider
         });
     }
 
+    public void AddMockMesh(Guid guid, int readDelayMs = 0)
+    {
+        var vertices = new[]
+        {
+            new Vertex { position = new float3(0, 0, 0), normal = new float3(0, 1, 0), tangent = new float4(1, 0, 0, 1), uv = new float2(0, 0), color = new Color128(1, 1, 1, 1) },
+            new Vertex { position = new float3(1, 0, 0), normal = new float3(0, 1, 0), tangent = new float4(1, 0, 0, 1), uv = new float2(1, 0), color = new Color128(1, 1, 1, 1) },
+            new Vertex { position = new float3(0, 1, 0), normal = new float3(0, 1, 0), tangent = new float4(1, 0, 0, 1), uv = new float2(0, 1), color = new Color128(1, 1, 1, 1) },
+        };
+        var indices = new uint[] { 0, 1, 2 };
+        var materialParts = new[]
+        {
+            new MeshContentMaterialPart { materialIndex = 0, indexStart = 0, indexCount = 3, vertexStart = 0, vertexCount = 3 }
+        };
+        var meshlets = new[]
+        {
+            new Meshlet
+            {
+                boundingSphere = new SphereBounds(new float3(0.5f, 0.5f, 0), 1.0f),
+                parentBoundingSphere = new SphereBounds(new float3(0.5f, 0.5f, 0), 1.0f),
+                boundingBox = new AABB(new float3(0, 0, 0), new float3(1, 1, 0)),
+                vertexOffset = 0,
+                triangleOffset = 0,
+                groupIndex = 0,
+                clusterError = 0,
+                parentError = 0,
+                vertexCount = 3,
+                triangleCount = 1,
+                localMaterialIndex = 0,
+                lodLevel = 0,
+            }
+        };
+        var groups = new[]
+        {
+            new MeshletGroup
+            {
+                boundingSphere = new SphereBounds(new float3(0.5f, 0.5f, 0), 1.0f),
+                boundingBox = new AABB(new float3(0, 0, 0), new float3(1, 1, 0)),
+                parentError = 0,
+                meshletStartIndex = 0,
+                meshletCount = 1,
+                lodLevel = 0,
+            }
+        };
+        var hierarchy = new[]
+        {
+            new MeshletHierarchyNode
+            {
+                minX = new float4(0, float.PositiveInfinity, float.PositiveInfinity, float.PositiveInfinity),
+                minY = new float4(0, float.PositiveInfinity, float.PositiveInfinity, float.PositiveInfinity),
+                minZ = new float4(0, float.PositiveInfinity, float.PositiveInfinity, float.PositiveInfinity),
+                maxX = new float4(1, float.NegativeInfinity, float.NegativeInfinity, float.NegativeInfinity),
+                maxY = new float4(1, float.NegativeInfinity, float.NegativeInfinity, float.NegativeInfinity),
+                maxZ = new float4(0, float.NegativeInfinity, float.NegativeInfinity, float.NegativeInfinity),
+                maxParentError = new float4(0),
+                nodeData = new uint4(0, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF),
+            }
+        };
+        var meshletVertices = new uint[] { 0, 1, 2 };
+        var meshletTriangles = new uint[] { 0 | (1u << 8) | (2u << 16) };
+
+        using var stream = new MemoryStream();
+        var header = new MeshContentHeader
+        {
+            magic = MeshContentHeader.MAGIC,
+            version = MeshContentHeader.VERSION,
+            vertexCount = (uint)vertices.Length,
+            indexCount = (uint)indices.Length,
+            materialPartCount = (uint)materialParts.Length,
+            meshletCount = (uint)meshlets.Length,
+            meshletGroupCount = (uint)groups.Length,
+            meshletHierarchyNodeCount = (uint)hierarchy.Length,
+            meshletVertexCount = (uint)meshletVertices.Length,
+            meshletTriangleCount = (uint)meshletTriangles.Length,
+            materialSlotCount = 1,
+            lodLevelCount = 1,
+            boundsMin = new float3(0, 0, 0),
+            boundsMax = new float3(1, 1, 0),
+        };
+
+        WriteStruct(stream, in header);
+        header.vertexOffset = (ulong)stream.Position; WriteSpan(stream, vertices);
+        header.indexOffset = (ulong)stream.Position; WriteSpan(stream, indices);
+        header.materialPartOffset = (ulong)stream.Position; WriteSpan(stream, materialParts);
+        header.meshletOffset = (ulong)stream.Position; WriteSpan(stream, meshlets);
+        header.meshletGroupOffset = (ulong)stream.Position; WriteSpan(stream, groups);
+        header.meshletHierarchyNodeOffset = (ulong)stream.Position; WriteSpan(stream, hierarchy);
+        header.meshletVertexOffset = (ulong)stream.Position; WriteSpan(stream, meshletVertices);
+        header.meshletTriangleOffset = (ulong)stream.Position; WriteSpan(stream, meshletTriangles);
+
+        stream.Position = 0;
+        WriteStruct(stream, in header);
+
+        AddMockAsset(guid, new MockAssetData
+        {
+            type = AssetType.Mesh,
+            data = stream.ToArray(),
+            readDelayMs = readDelayMs
+        });
+    }
+
+    private static void WriteStruct<T>(Stream stream, ref readonly T value)
+        where T : unmanaged
+    {
+        stream.Write(MemoryMarshal.AsBytes(MemoryMarshal.CreateReadOnlySpan(in value, 1)));
+    }
+
+    private static void WriteSpan<T>(Stream stream, ReadOnlySpan<T> value)
+        where T : unmanaged
+    {
+        stream.Write(MemoryMarshal.AsBytes(value));
+    }
+
     public AssetType GetAssetType(Guid guid)
     {
         return _assets.TryGetValue(guid, out var asset) ? asset.type : AssetType.Unknown;

src/Test/Ghost.UnitTest/MockingEnvironment/MockingResourceDatabase.cs

@@ -1,6 +1,7 @@
 using Ghost.Core;
 using Ghost.Graphics.RHI;
 using System.Collections.Concurrent;
+using System.Runtime.InteropServices;
 
 namespace Ghost.UnitTest.MockingEnvironment;
 
@@ -13,6 +14,7 @@ internal unsafe class MockingResourceDatabase : IResourceDatabase
         public string? name;
         public int refCount = 1;
         public bool isShared;
+        public unsafe void* mappedData;
     }
 
     private readonly ConcurrentDictionary<ulong, MockResourceRecord> _resources = new();
@@ -118,9 +120,21 @@ internal unsafe class MockingResourceDatabase : IResourceDatabase
 
     public void* MapResource(Handle<GPUResource> handle, uint subResource, ResourceRange? readRange)
     {
-        // Real pointers are tricky in mocks unless native mem is allocated.
+        if (!_resources.TryGetValue(GetKey(handle), out var record))
-        // Usually unit tests don't do CPU readbacks directly on the raw pointer unless necessary.
+        {
-        throw new NotSupportedException("MapResource is not supported in MockingResourceDatabase. Use a custom mechanism for tests.");
+            return null;
+        }
+
+        lock (record)
+        {
+            if (record.mappedData == null)
+            {
+                var size = record.desc.Type == ResourceType.Buffer ? Math.Max(1UL, record.desc.BufferDescriptor.Size) : 1UL;
+                record.mappedData = NativeMemory.Alloc((nuint)size);
+            }
+
+            return record.mappedData;
+        }
     }
 
     public void ReleaseResource(Handle<GPUResource> handle)
@@ -137,6 +151,12 @@ internal unsafe class MockingResourceDatabase : IResourceDatabase
                 record.refCount--;
                 if (record.refCount <= 0)
                 {
+                    if (record.mappedData != null)
+                    {
+                        NativeMemory.Free(record.mappedData);
+                        record.mappedData = null;
+                    }
+
                     _resources.TryRemove(GetKey(handle), out _);
                 }
             }
@@ -207,6 +227,15 @@ internal unsafe class MockingResourceDatabase : IResourceDatabase
 
     public void Dispose()
     {
+        foreach (var record in _resources.Values)
+        {
+            if (record.mappedData != null)
+            {
+                NativeMemory.Free(record.mappedData);
+                record.mappedData = null;
+            }
+        }
+
         _resources.Clear();
         _samplers.Clear();
     }

src/ThridParty/Ghost.DXC/Api.cs

@@ -15,9 +15,9 @@ public partial class Api
         // NOTE: Currently only support Windows.
         if (libraryName == "dxcompiler")
         {
-            NativeLibrary.TryLoad("runtimes/win-x64/native/dxil.dll", out _);
+            NativeLibrary.TryLoad(Path.Combine(AppContext.BaseDirectory, "runtimes", "win-x64", "native", "dxil.dll"), out _);
 
-            if (NativeLibrary.TryLoad("runtimes/win-x64/native/dxcompiler.dll", out var dxcHandle))
+            if (NativeLibrary.TryLoad(Path.Combine(AppContext.BaseDirectory, "runtimes", "win-x64", "native", "dxcompiler.dll"), out var dxcHandle))
             {
                 return dxcHandle;
             }

src/ThridParty/Ghost.MeshOptimizer/Api.cs

@@ -22,7 +22,7 @@ public partial class Api
                         OperatingSystem.IsMacOS() ? ".dylib" : "";
 
             var arch = Environment.Is64BitProcess ? "x64" : "x86";
-            var nativeDllDir = Path.Combine("./runtimes", platform + "-" + arch, "native");
+            var nativeDllDir = Path.Combine(AppContext.BaseDirectory, "runtimes", platform + "-" + arch, "native");
 
             return NativeLibrary.Load(Path.Combine(nativeDllDir, libraryName + ext));
         });

src/ThridParty/Ghost.Nvtt/Api.cs

@@ -17,7 +17,7 @@ public partial class Api
                         OperatingSystem.IsMacOS() ? ".dylib" : "";
 
             var arch = Environment.Is64BitProcess ? "x64" : "x86";
-            var nativeDllDir = Path.Combine("./runtimes", platform + "-" + arch, "native");
+            var nativeDllDir = Path.Combine(AppContext.BaseDirectory, "runtimes", platform + "-" + arch, "native");
 
             return NativeLibrary.Load(Path.Combine(nativeDllDir, libraryName + ext));
         });

src/ThridParty/Ghost.StbI/Api.cs

@@ -17,7 +17,7 @@ public partial class Api
                         OperatingSystem.IsMacOS() ? ".dylib" : "";
 
             var arch = Environment.Is64BitProcess ? "x64" : "x86";
-            var nativeDllDir = Path.Combine("./runtimes", platform + "-" + arch, "native");
+            var nativeDllDir = Path.Combine(AppContext.BaseDirectory, "runtimes", platform + "-" + arch, "native");
 
             return NativeLibrary.Load(Path.Combine(nativeDllDir, libraryName + ext));
         });

src/ThridParty/Ghost.Ufbx/Api.cs

@@ -22,8 +22,7 @@ public partial class Api
                         OperatingSystem.IsMacOS() ? ".dylib" : "";
 
             var arch = Environment.Is64BitProcess ? "x64" : "x86";
-            var nativeDllDir = Path.Combine("./runtimes", platform + "-" + arch, "native");
+            var nativeDllDir = Path.Combine(AppContext.BaseDirectory, "runtimes", platform + "-" + arch, "native");
-
             return NativeLibrary.Load(Path.Combine(nativeDllDir, libraryName + ext));
         });
     }