feat: LOD 网格分级——meshopt 解析期简化 + 按距离/级联选级

vendored meshoptimizer 1.2（submodule 环境故障改直接 vendor）。Mesh
多 LOD：各级索引连续拼进同一 index buffer（共享顶点，LodRange 区间
选择），解析期 meshopt_simplify 生成链（LOD0=原始，每级目标减半，
相对误差 1e-2，小网格复用上级）；都在 worker 线程，加载零额外卡顿。

SceneRenderer 按 (mesh, LOD) 聚合 batch（lookup key = 指针<<8|lod）：
主视图按屏占比近似 radius/dist 选级（阈值 10/20 倍半径）；阴影级联
按级联序降级（越远越简）。Draw 按 batch.lod 选索引区间。

A/B 对比（100 背包 10×10，RTX 5060 Laptop，vsync off）：
- 纯背包：LOD 开 93-95 fps / 关 90-107 fps —— 无显著差异
- 加 SunTemple：LOD 开 52-56 / 关 51-55 —— 无显著差异
结论：当前场景瓶颈不在顶点数（5060 顶点吞吐富余），LOD 基础设施
保留（几何复杂资产/低端 GPU/更大场景生效），帧率问题转向 Tracy
GPU 时间线定位真实瓶颈。

坑：LodRange 记录"LOD 不足复用最后一级"时 first 不得继续累加
（buffer 无重复数据，累加必越界——VUID-08798 抓的）。

Lib/meshoptimizer/.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,8 @@
+---
+name: Bug report
+about: Create a report if you've found a bug in this project; please use GitHub Discussions instead if you are uncertain or the bug may be in your code.
+title: ''
+labels: bug
+assignees: ''
+
+---

Lib/meshoptimizer/.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,5 @@
+blank_issues_enabled: false
+contact_links:
+  - name: Questions and ideas
+    url: https://github.com/zeux/meshoptimizer/discussions
+    about: Please use GitHub Discussions if you have questions or ideas to discuss.

Lib/meshoptimizer/.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,8 @@
+---
+name: Feature request
+about: Suggest a feature for this project; please use GitHub Discussions if your idea is not sufficiently concrete.
+title: ''
+labels: enhancement
+assignees: ''
+
+---

Lib/meshoptimizer/.github/codecov.yml

@@ -0,0 +1,11 @@
+comment: false
+
+coverage:
+  status:
+    project: off
+    patch: off
+
+ignore:
+  - demo
+  - extern
+  - tools

Lib/meshoptimizer/.github/workflows/build.yml

@@ -0,0 +1,240 @@
+name: build
+
+on:
+  push:
+    branches:
+      - 'master'
+    paths-ignore:
+      - '*.md'
+  pull_request:
+    paths-ignore:
+      - '*.md'
+
+jobs:
+  unix:
+    strategy:
+      matrix:
+        os:
+          [
+            { name: ubuntu, version: ubuntu-latest },
+            { name: ubuntu-arm, version: ubuntu-24.04-arm },
+            { name: ubuntu-clang, version: ubuntu-latest },
+            { name: macos, version: macos-latest },
+          ]
+    name: ${{matrix.os.name}}
+    runs-on: ${{matrix.os.version}}
+    env:
+      werror: 1
+    steps:
+      - uses: actions/checkout@v6
+      - name: work around ASLR+ASAN compatibility
+        run: sudo sysctl -w vm.mmap_rnd_bits=28
+        if: matrix.os.name == 'ubuntu'
+      - name: enable clang
+        run: echo CXX=clang++ >Makefile.config
+        if: matrix.os.name == 'ubuntu-clang'
+      - name: make test
+        run: |
+          make -j2 config=sanitize test
+          make -j2 config=debug test
+          make -j2 config=release test
+          make -j2 config=coverage test
+          make -j2 config=coverage-scalar test
+      - name: make gltfpack
+        run: make -j2 config=release gltfpack
+      - name: upload coverage
+        run: |
+          find . -type f -name '*.gcno' -exec gcov -p {} +
+          sed -i -e "s/#####\(.*\)\(\/\/ unreachable.*\)/    -\1\2/" *.gcov
+          bash <(curl -s https://codecov.io/bash) -f './src*.gcov' -X search -t ${{secrets.CODECOV_TOKEN}} -B ${{github.ref}}
+        if: matrix.os.name != 'ubuntu-clang'
+
+  windows:
+    strategy:
+      matrix:
+        arch:
+          [
+            { name: windows, runner: windows-latest, arch: x64 },
+            { name: windows-x86, runner: windows-latest, arch: Win32 },
+            { name: windows-arm, runner: windows-11-arm, arch: ARM64 },
+          ]
+    name: ${{matrix.arch.name}}
+    runs-on: ${{matrix.arch.runner}}
+    steps:
+      - uses: actions/checkout@v6
+      - name: cmake configure
+        run: cmake . -DMESHOPT_BUILD_DEMO=ON -DMESHOPT_BUILD_GLTFPACK=ON -DMESHOPT_WERROR=ON -DCMAKE_MSVC_RUNTIME_LIBRARY="MultiThreaded$<$<CONFIG:Debug>:Debug>" -A ${{matrix.arch.arch}}
+      - name: cmake test
+        shell: bash # necessary for fail-fast
+        run: |
+          cmake --build . -- -property:Configuration=Debug -verbosity:minimal
+          Debug/meshoptdemo.exe demo/pirate.obj
+          cmake --build . -- -property:Configuration=Release -verbosity:minimal
+          Release/meshoptdemo.exe demo/pirate.obj
+
+  nodejs:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/setup-node@v6
+        with:
+          node-version: '16'
+      - name: test decoder
+        run: node js/meshopt_decoder.test.js
+      - name: test simd decoder
+        run: node --experimental-wasm-simd js/meshopt_decoder.test.js
+      - name: test encoder
+        run: node js/meshopt_encoder.test.js
+      - name: test simplifier
+        run: node js/meshopt_simplifier.test.js
+      - name: test clusterizer
+        run: node js/meshopt_clusterizer.test.js
+      - name: test tangents
+        run: node js/meshopt_tangents.test.js
+      - name: check typescript declarations
+        run: npx --yes -p typescript@6 tsc --noEmit --moduleResolution node16 --module node16 --strict js/index.d.ts
+      - name: check es5
+        run: |
+          npm install -g es-check@7.2.1
+          npx es-check --module es5 js/meshopt_decoder.mjs js/meshopt_encoder.js js/meshopt_simplifier.js js/meshopt_clusterizer.js js/meshopt_tangents.js
+          npx es-check --module es2020 gltf/library.js
+
+  gltfpack:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/checkout@v6
+        with:
+          repository: KhronosGroup/glTF-Sample-Assets
+          path: glTF-Sample-Assets
+      - name: work around ASLR+ASAN compatibility
+        run: sudo sysctl -w vm.mmap_rnd_bits=28
+      - name: make
+        run: make -j2 config=sanitize gltfpack
+      - name: test
+        run: find glTF-Sample-Assets -name '*.gltf' -or -name '*.glb' | xargs -P 2 -L 16 -d '\n' ./gltfpack -cc -test
+      - name: pack
+        run: find glTF-Sample-Assets -name '*.gltf' | grep -v '\-Draco/' | xargs -P 2 -L 16 -d '\n' -I '{}' ./gltfpack -i '{}' -o '{}pack.gltf'
+      - name: validate
+        run: |
+          curl -sL $VALIDATOR | tar xJ
+          find glTF-Sample-Assets -name '*.gltfpack.gltf' | xargs -P 2 -L 1 -d '\n' ./gltf_validator -r -a
+        env:
+          VALIDATOR: https://github.com/KhronosGroup/glTF-Validator/releases/download/2.0.0-dev.3.10/gltf_validator-2.0.0-dev.3.10-linux64.tar.xz
+
+  gltfpack-js:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/setup-node@v6
+        with:
+          node-version: '18'
+      - name: install wasi
+        run: |
+          curl -sL https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-$VERSION/wasi-sdk-$VERSION.0-x86_64-linux.deb > wasi-sdk.deb
+          sudo dpkg -i wasi-sdk.deb
+        env:
+          VERSION: 32
+      - name: build
+        run: |
+          make -j2 -B gltf/library.wasm js
+          git status
+      - name: test
+        run: |
+          node gltf/cli.js -i demo/pirate.obj -o pirate.glb -v
+          node gltf/cli.js -i `pwd`/pirate.glb -o pirate-repack.glb -cc -v
+          wc -c pirate.glb pirate-repack.glb
+          node js/meshopt_decoder.test.js
+          node js/meshopt_encoder.test.js
+          node js/meshopt_simplifier.test.js
+          node js/meshopt_clusterizer.test.js
+          node js/meshopt_tangents.test.js
+
+  gltfpack-full:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/checkout@v6
+        with:
+          repository: zeux/basis_universal
+          ref: gltfpack
+          path: basis_universal
+      - uses: actions/checkout@v6
+        with:
+          repository: webmproject/libwebp
+          ref: 1.6.0
+          path: libwebp
+      - name: cmake configure
+        run: cmake . -DMESHOPT_BUILD_GLTFPACK=ON -DMESHOPT_GLTFPACK_BASISU_PATH=basis_universal -DMESHOPT_GLTFPACK_LIBWEBP_PATH=libwebp
+      - name: cmake build
+        run: cmake --build . --target gltfpack -j 4
+
+  gltfpack-coverage:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/checkout@v6
+        with:
+          repository: zeux/basis_universal
+          ref: gltfpack
+          path: basis_universal
+      - uses: actions/checkout@v6
+        with:
+          repository: KhronosGroup/glTF-Sample-Assets
+          path: glTF-Sample-Assets
+      - name: build basisu
+        run: |
+          cd basis_universal
+          cmake . -D CMAKE_BUILD_TYPE=Debug
+          make -j4 basisu_encoder
+      - name: make
+        run: make -j2 config=coverage BASISU=basis_universal gltfpack
+      - name: test
+        run: |
+          find glTF-Sample-Assets -name '*.gltf' -or -name '*.glb' | xargs -P 2 -L 16 -d '\n' ./gltfpack -cc -test
+          ./gltfpack -test demo/pirate.obj -si 0.5
+          ./gltfpack -test demo/pirate.obj -si 0.5 -slb -se 0.02
+          ./gltfpack -test demo/pirate.obj -si 0.1 -sa
+          ./gltfpack -test demo/pirate.obj -noq
+          ./gltfpack -test demo/pirate.obj -vp 16 -vt 16 -vn 16 -vc 16
+          ./gltfpack -test demo/pirate.obj -vpf -vtf -vnf
+          ./gltfpack -test demo/pirate.obj -vi -c
+          ./gltfpack -test glTF-Sample-Assets/Models/ABeautifulGame/glTF/ABeautifulGame.gltf -mi -c
+          ./gltfpack -test glTF-Sample-Assets/Models/ABeautifulGame/glTF/ABeautifulGame.gltf -kn -km -ke
+          ./gltfpack -test glTF-Sample-Assets/Models/ABeautifulGame/glTF/ABeautifulGame.gltf -si 0.1 -sp
+          ./gltfpack -test glTF-Sample-Assets/Models/ABeautifulGame/glTF/ABeautifulGame.gltf -si 0.1 -sv
+          ./gltfpack -test glTF-Sample-Assets/Models/BoxTextured/glTF/BoxTextured.gltf -vpf -vtf -c
+          ./gltfpack -test glTF-Sample-Assets/Models/BoxTextured/glTF/BoxTextured.gltf -vpf -vtf -cc
+          ./gltfpack -test glTF-Sample-Assets/Models/BoxTextured/glTF/BoxTextured.gltf -tc
+          ./gltfpack -test glTF-Sample-Assets/Models/BoxTextured/glTF/BoxTextured.gltf -tc -tq color 10 -tu normal,attrib -ts attrib 0.5 -tl color 512
+          ./gltfpack -test glTF-Sample-Assets/Models/BoxTextured/glTF/BoxTextured.gltf -tr
+          ./gltfpack -test glTF-Sample-Assets/Models/BoxTextured/glTF/BoxTextured.gltf -tc -ts 0.5 -tl 64
+          ./gltfpack -test glTF-Sample-Assets/Models/BoxTextured/glTF/BoxTextured.gltf -tc color -tfy -tq 4 -tj 1
+          ./gltfpack -test glTF-Sample-Assets/Models/CesiumMan/glTF/CesiumMan.gltf -tu -ts 0.6 -tp -ar 0
+          ./gltfpack -test glTF-Sample-Assets/Models/CesiumMan/glTF/CesiumMan.gltf -gt -kv
+          ./gltfpack -test glTF-Sample-Assets/Models/PrimitiveModeNormalsTest/glTF/PrimitiveModeNormalsTest.gltf -si 0.5
+          ./gltfpack -test glTF-Sample-Assets/Models/VertexColorTest/glTF/VertexColorTest.gltf -si 0.5 -vc 12
+          ./gltfpack -test glTF-Sample-Assets/Models/SimpleMeshes/glTF/SimpleMeshes.gltf -mm
+          ./gltfpack -test glTF-Sample-Assets/Models/SimpleMeshes/glTF/SimpleMeshes.gltf -kn
+          echo newmtl Leather > demo/pirate.mtl
+          echo map_Kd leather.jpg >> demo/pirate.mtl
+          echo map_d leather.jpg >> demo/pirate.mtl
+          ./gltfpack -test demo/pirate.obj
+      - name: test output
+        run: |
+          ./gltfpack || true
+          ./gltfpack -h || true
+          ./gltfpack -i glTF-Sample-Assets/Models/BoxTextured/glTF/BoxTextured.gltf -o box.glb -vv -r box.json
+          ./gltfpack -i glTF-Sample-Assets/Models/BoxTextured/glTF/BoxTextured.gltf -o box.gltf -cf
+      - name: upload coverage
+        run: |
+          find . -type f -name '*.gcno' -exec gcov -p {} +
+          sed -i -e "s/#####\(.*\)\(\/\/ unreachable.*\)/    -\1\2/" *.gcov
+          bash <(curl -s https://codecov.io/bash) -f './gltf*.gcov' -X search -t ${{secrets.CODECOV_TOKEN}} -B ${{github.ref}}
+
+  macos-iphone:
+    runs-on: macos-14
+    steps:
+      - uses: actions/checkout@v6
+      - name: make
+        run: make -j2 config=iphone

Lib/meshoptimizer/.github/workflows/cifuzz.yml

@@ -0,0 +1,33 @@
+name: CIFuzz
+
+on:
+  push:
+    branches:
+      - 'master'
+    paths-ignore:
+      - '*.md'
+
+jobs:
+  Fuzzing:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Build Fuzzers
+        id: build
+        uses: google/oss-fuzz/infra/cifuzz/actions/build_fuzzers@master
+        with:
+          oss-fuzz-project-name: 'meshoptimizer'
+          dry-run: false
+          language: c++
+      - name: Run Fuzzers
+        uses: google/oss-fuzz/infra/cifuzz/actions/run_fuzzers@master
+        with:
+          oss-fuzz-project-name: 'meshoptimizer'
+          fuzz-seconds: 30
+          dry-run: false
+          language: c++
+      - name: Upload Crash
+        uses: actions/upload-artifact@v7
+        if: failure() && steps.build.outcome == 'success'
+        with:
+          name: artifacts
+          path: ./out/artifacts

Lib/meshoptimizer/.github/workflows/release.yml

@@ -0,0 +1,77 @@
+name: release
+
+on:
+  push:
+    branches:
+      - 'master'
+    paths-ignore:
+      - '*.md'
+
+jobs:
+  gltfpack:
+    strategy:
+      matrix:
+        os: [{ name: windows, version: windows-latest }, { name: ubuntu, version: ubuntu-22.04 }, { name: macos, version: macos-14 }]
+    name: gltfpack-${{matrix.os.name}}
+    runs-on: ${{matrix.os.version}}
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/checkout@v6
+        with:
+          repository: zeux/basis_universal
+          ref: gltfpack
+          path: basis_universal
+      - uses: actions/checkout@v6
+        with:
+          repository: webmproject/libwebp
+          ref: 1.6.0
+          path: libwebp
+      - name: cmake configure
+        run: cmake . -DMESHOPT_BUILD_GLTFPACK=ON -DMESHOPT_GLTFPACK_BASISU_PATH=basis_universal -D MESHOPT_GLTFPACK_LIBWEBP_PATH=libwebp -DCMAKE_MSVC_RUNTIME_LIBRARY="MultiThreaded" -DCMAKE_BUILD_TYPE=Release
+      - name: cmake configure x64
+        run: cmake . -DSSE=ON -DBASISU_SSE=ON
+        if: matrix.os.name == 'ubuntu'
+      - name: cmake build
+        run: cmake --build . --target gltfpack --config Release -j 3
+      - uses: actions/upload-artifact@v7
+        with:
+          name: gltfpack-windows
+          path: Release/gltfpack.exe
+        if: matrix.os.name == 'windows'
+      - uses: actions/upload-artifact@v7
+        with:
+          name: gltfpack-${{matrix.os.name}}
+          path: gltfpack
+        if: matrix.os.name != 'windows'
+
+  nodejs:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/setup-node@v6
+        with:
+          node-version: '18'
+      - name: install wasi
+        run: |
+          curl -sL https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-$VERSION/wasi-sdk-$VERSION.0-x86_64-linux.deb > wasi-sdk.deb
+          sudo dpkg -i wasi-sdk.deb
+        env:
+          VERSION: 32
+      - name: build
+        run: |
+          make -j2 -B gltf/library.wasm js
+          git status
+      - name: npm pack
+        run: |
+          cp LICENSE.md gltf/
+          cp LICENSE.md js/
+          cd gltf && npm pack && cd ..
+          cd js && npm pack && cd ..
+      - uses: actions/upload-artifact@v7
+        with:
+          name: gltfpack-npm
+          path: gltf/gltfpack-*.tgz
+      - uses: actions/upload-artifact@v7
+        with:
+          name: meshoptimizer-npm
+          path: js/meshoptimizer-*.tgz