alcesium-terrain-maker

High-performance GeoTIFF → Cesium quantized-mesh-1.0 terrain tile generator.

Python API + Cython/AVX512 native core（默认开启 AVX512，需 CPU 支持）。GDAL is required at runtime (not bundled in the wheel).

Requirements

• Python >= 3.11
• CMake >= 3.22, C++17 compiler, Ninja
• GDAL >= 3.4 with Python bindings (osgeo)
• NumPy (build + runtime for tests)

Installing GDAL

Conda (recommended on Windows):

conda install -c conda-forge gdal

Linux:

sudo apt install gdal-bin libgdal-dev python3-gdal

Build & Install

# 安装到当前环境（开发）
uv sync --extra dev
uv pip install -e ".[dev]"

# 打一个 wheel（当前 Python 版本）→ dist/
uv build --wheel --out-dir dist

# Windows：注入 MSVC 后构建（推荐）
.\scripts\build_wheel.ps1

# 全量：Windows 3.11–3.14 + Linux manylinux（需 Docker）
.\scripts\build_local_wheels.ps1

# 上传 PyPI
.\scripts\upload_wheels.ps1

详见 scripts/README.md。

默认 wheel 开启 AVX512（性能优先）。在不支持 AVX512 的老 CPU 上需关闭后重编：

uv build --wheel -Ccmake.define.ATM_USE_AVX512=OFF
# 或仅 AVX2：
uv build --wheel -Ccmake.define.ATM_USE_AVX512=OFF -Ccmake.define.ATM_USE_AVX2=ON
# 或完全可移植（无 SIMD 指令集要求）：
uv build --wheel -Ccmake.define.ATM_USE_AVX512=OFF -Ccmake.define.ATM_USE_AVX2=OFF

PowerShell 脚本可加 -Portable：.\scripts\build_wheel.ps1 -Portable

Python API

from pathlib import Path
from alcesium_terrain_maker import TerrainBuilder, TerrainConfig

config = TerrainConfig(
    profile="geodetic",       # or "mercator"
    overlap_mode="MEAN",      # LAST | FIRST | MEAN | MIN | MAX
    buffer_m=500.0,
    buffer_mode="FADE",       # EXTEND | FADE
    max_zoom=14,
    thread_count=16,
)

builder = TerrainBuilder(config)
result = builder.build(
    inputs=[Path("dem_a.tif"), Path("dem_b.tif")],
    output_dir=Path("terrain_out"),
)

print(result.tiles_written, result.layer_json_path)

Multi-GeoTIFF overlap

Each source is sampled independently per tile. Overlap pixels are merged using overlap_mode:

Boundary buffer

buffer_m extends each source outward. Applied per-source during tile sampling (not by merging rasters):

• EXTEND: outer ring height copied from nearest valid edge pixel
• FADE: linear decay toward 0; pixels originally below 0 stay frozen in the buffer zone

Output layout

terrain_out/
├── layer.json
└── {z}/{x}/{y}.terrain   # gzip-compressed quantized-mesh-1.0

Load in CesiumJS

const viewer = new Cesium.Viewer("cesiumContainer", {
  terrainProvider: await Cesium.CesiumTerrainProvider.fromUrl("./terrain_out/"),
});

Project layout

src/alcesium_terrain_maker/   # Python + Cython sources
extern/zlib/                  # zlib (FetchContent at build time)
extern/mesh_simplify/         # Chunked LOD grid simplification (C++)

Tests

pytest tests/

Performance tips

• Use COG / tiled GeoTIFF (gdal_translate -co TILED=YES -co BLOCKXSIZE=65)
• Set thread_count to CPU core count
• Input elevation should be ellipsoidal heights in meters (WGS84)