[Performance] Automatic LOD chains for the models of a .untoldpack

Package.swift

@@ -64,6 +64,10 @@ let package = Package(
         // @UntoldMenu, reflection, scene storage and the per-frame system. Platform neutral.
         .library(name: "UntoldComponentKit", targets: ["UntoldComponentKit"]),
 
+        // Cook-time mesh work: the automatic LOD chains of cooked models. For tools
+        // that cook assets (the CLI, an editor), not for the apps that load them.
+        .library(name: "UntoldEngineMeshCook", targets: ["UntoldEngineMeshCook"]),
+
         // NOTE: Demo executables are intentionally NOT declared as products so they
         // stay hidden from consumers of the package. SwiftPM creates implicit
         // products for executable targets in the root package, so they remain
@@ -88,6 +92,14 @@ let package = Package(
                 .headerSearchPath("include"),
             ]
         ),
+        // meshoptimizer (MIT), unmodified: the mesh simplifier behind the cook's automatic
+        // LOD chains. UntoldEngineMeshCook calls it from Swift through its C API.
+        .target(
+            name: "CMeshOptimizer",
+            path: "Sources/CMeshOptimizer",
+            exclude: ["LICENSE.md", "README.md"],
+            publicHeadersPath: "include"
+        ),
         .target(
             name: "UntoldEngine",
             dependencies: ["CShaderTypes"],
@@ -121,6 +133,17 @@ let package = Package(
             ]
         ),
 
+        // The cook's mesh work. A module of its own so that UntoldEngine does not import
+        // CMeshOptimizer: whatever compiles against a built UntoldEngine module without
+        // SwiftPM (the editor compiles a project's components that way) would otherwise
+        // need the module map of that C++ library as well.
+        .target(
+            name: "UntoldEngineMeshCook",
+            dependencies: ["UntoldEngine", "CMeshOptimizer"],
+            path: "Sources/UntoldEngineMeshCook",
+            swiftSettings: [.swiftLanguageMode(.v6)]
+        ),
+
         // Vision OS target
         .target(
             name: "UntoldEngineXR",
@@ -273,14 +296,14 @@ let package = Package(
         ),
         .testTarget(
             name: "UntoldEngineTests",
-            dependencies: ["UntoldEngine", "UntoldEngineShaderSupport"],
+            dependencies: ["UntoldEngine", "UntoldEngineMeshCook", "UntoldEngineShaderSupport"],
             path: "Tests/UntoldEngineTests",
             swiftSettings: [.swiftLanguageMode(.v6)]
         ),
         // Render-specific test target
         .testTarget(
             name: "UntoldEngineRenderTests",
-            dependencies: ["UntoldEngine"],
+            dependencies: ["UntoldEngine", "UntoldEngineMeshCook"],
             path: "Tests/UntoldEngineRenderTests",
             exclude: ["Resources/compare_psnr.py"],
             resources: [

Sources/CMeshOptimizer/LICENSE.md

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2016-2026 Arseny Kapoulkine
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

Sources/CMeshOptimizer/README.md

@@ -0,0 +1,14 @@
+# CMeshOptimizer
+
+Part of [meshoptimizer](https://github.com/zeux/meshoptimizer) 1.3 (tag `v1.3`), by Arseny Kapoulkine, under the MIT License (see `LICENSE.md`). The files are unmodified copies:
+
+- `include/meshoptimizer.h` is `src/meshoptimizer.h`.
+- The `.cpp` files are those of `src/` that the engine uses: the simplifier, the index generator, the vertex cache and vertex fetch optimizers, and the allocator they share. The header declares the whole library; a function of a file that is not here does not link.
+
+The `UntoldEngineMeshCook` module calls the C API from Swift (`import CMeshOptimizer`); no C++ interoperability is needed. It is used by the asset cook, not by the renderer: `UntoldMeshLODCooker` builds the automatic LOD chain of a cooked model with the simplifier.
+
+Only `UntoldEngineMeshCook` imports this module. `UntoldEngine` must not: code that is compiled against a built `UntoldEngine` module without SwiftPM (the editor compiles a project's components that way) would then need this library's module map too, and fail with "missing required module 'CMeshOptimizer'".
+
+## Updating
+
+Replace the files with those of the new tag and update the version above. Add a file of `src/` when the engine starts to use it. Do not edit the files here: local changes would be lost on the next update.

Sources/CMeshOptimizer/allocator.cpp

@@ -0,0 +1,21 @@
+// This file is part of meshoptimizer library; see meshoptimizer.h for version/license details
+#include "meshoptimizer.h"
+
+#include <assert.h>
+
+#ifdef MESHOPTIMIZER_ALLOC_EXPORT
+meshopt_Allocator::Storage& meshopt_Allocator::storage()
+{
+	static Storage s = {::operator new, ::operator delete };
+	return s;
+}
+#endif
+
+void meshopt_setAllocator(void* (MESHOPTIMIZER_ALLOC_CALLCONV* allocate)(size_t), void (MESHOPTIMIZER_ALLOC_CALLCONV* deallocate)(void*))
+{
+	assert(allocate && deallocate);
+
+	meshopt_Allocator::Storage& s = meshopt_Allocator::storage();
+	s.allocate = allocate;
+	s.deallocate = deallocate;
+}