A full-featured 3D asset library in C, designed for low overhead and maximum performance. Import, export and process scenes, meshes, materials, animations, skins and morph targets through one API.

📚 Documentation

API declarations and inline documentation live in include/ak. See the documentation and C samples for usage, or the notes on extensions and decoders and extras.

Supported formats

Import and export:

• glTF 2.0 — .gltf and .glb, external or embedded resources
• COLLADA 1.4 / 1.5 — .dae
• Wavefront OBJ — .obj and .mtl
• STL — ASCII and binary
• PLY — ASCII and binary; meshes and point clouds
• 3MF — packaged models, resources and manufacturing data

Additional import support:

• Gaussian-splat PLY — scale, rotation, opacity and spherical harmonics
• SPZ — standalone .spz and glTF Gaussian-splat compression
• L-GSC — standalone .lgsc and glTF/GLB Gaussian-splat compression

Draco, meshoptimizer, KTX2/BasisU and SPZ decoding use optional side libraries, loaded on demand. They are not linked into the core C library. L-GSC decoding is built into the C library and uses the existing libdeflate dependency. See L-GSC support for the glTF draft version.

🚀 Features

• Scene hierarchies, shared instances, cameras, lights and GPU instancing.
• Points, lines, polygons, triangle lists, strips and fans; spline and BRep geometry.
• PBR and classic materials, texture transforms, variants and instance bindings; clearcoat, sheen, transmission, volume, iridescence and anisotropy.
• Animation clips, sampler evaluation, channel resolution and transform baking.
• Skin weights and morph targets with inspection and interleaving helpers.
• Mesh editing, triangulation, normal generation, index remapping and bounding boxes.
• Coordinate conversion for units, up axis and handedness.
• 3MF build items, components, materials, textures and manufacturing metadata.
• Gaussian splats and compressed splat decoding.
• Hierarchical memory ownership and custom allocators.
• ID, SID and URL resolution; application-defined extras and user data.

AssetKit is renderer-independent. Accessors expose their component type, stride and normalization directly. Source-backed glTF accessors and u8/u16/u32 indices avoid unnecessary copies and widening; quantized attributes can be kept in their original storage. File loading uses memory mapping where available.

Usage

Include <ak/assetkit.h> and link with assetkit:

#include <ak/assetkit.h>
#include <stdio.h>

int main(int argc, char **argv) {
  AkGeometry *geom;
  AkScene    *scene;
  AkMesh     *mesh;
  AkNode     *root;
  AkDoc      *doc;

  doc = NULL;
  if (argc != 2 || ak_load(&doc, argv[1], AK_FILE_TYPE_AUTO) != AK_OK)
    return 1;

  if ((scene = ak_activeSceneOrFirst(doc))) {
    printf("scene: %s\n", ak_nameOrUnnamed(scene->name));
    for (root = ak_sceneRoots(scene); root; root = root->next)
      printf("  root: %s\n", ak_nameOrUnnamed(root->name));
  }

  for (geom = doc->lib.geometries.first; geom; geom = geom->next) {
    if (!(mesh = ak_meshFromGeometry(geom)))
      continue;
    printf("mesh: %s, primitives: %u\n", ak_nameOrUnnamed(geom->name), mesh->primitiveCount);
  }

  ak_free(doc);
  return 0;
}

The scene and mesh pointers above belong to the document. ak_free(doc) releases the document and everything it owns, including materials, animations and buffers. Custom builders can use AkHeapAllocator and the ak_heap_* functions for the same hierarchical ownership with their own allocator.

Use ak_exportFile() to write a loaded document, or ak_convert() to load and export in one call:

if (ak_convert("scene.dae", "scene.glb", AK_FILE_TYPE_AUTO) != AK_OK)
  return 1;

More examples: scene traversal, mesh access, materials, animation and skin/morph.

Ownership and color space

Keep document-owned pointers only as long as the document lives. Retaining a child does not make it survive destruction of its parent. Independently allocated helper outputs have their own lifetime; follow the function's ownership contract.

AkColor, material factors, vertex colors and light colors use linear-sRGB. Texture colorSpace applies to sampled pixels, not these constant values: color textures use sRGB; normal, metallic, roughness and other data textures use linear values. Alpha is linear. Storage type is separate from color space: linear values can still use normalized integer storage.

🔨 Building

CMake 3.16 or newer; macOS, Linux and Windows. The core builds as C11 by default and exposes a C API usable from C++.

git clone --recursive https://github.com/recp/assetkit.git
cd assetkit
cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build --parallel
cmake --install build

For Visual Studio or Xcode, add --config Release to the build and install commands. For an existing checkout, run git submodule update --init --recursive. Installation is optional.

Common CMake options:

Option	Default	Purpose
AK_SHARED / AK_STATIC	ON / OFF	Shared or static core library
AK_BUILD_EXPORTERS	ON	Export support; disable for import-only builds
AK_BUILD_DECODER_SHIMS	ON	Optional Draco, meshoptimizer, SPZ and KTX2 decoders
AK_FETCH_DEPS	ON	Fetch missing decoder dependencies into the build tree
AK_BUILD_CLI	ON	Command-line inspection and conversion tool
AK_BUILD_SAMPLES	OFF	C usage examples
AK_ENABLE_LTO	OFF	Link-time optimization

Exporters and decoder shims can also be disabled individually. See CMakeLists.txt for all options and EXTENSIONS.md for decoder setup. Set AK_FETCH_DEPS=OFF for builds that must not fetch decoder dependencies.

CMake integration

From an installed package:

find_package(assetkit CONFIG REQUIRED)
target_link_libraries(my_app PRIVATE assetkit::assetkit)

Or from a checkout in your project:

add_subdirectory(external/assetkit)
target_link_libraries(my_app PRIVATE assetkit::assetkit)

Command line

After installation:

assetkit --inspect scene.glb
assetkit --convert scene.dae scene.glb

Samples

cmake -S . -B build -DAK_BUILD_SAMPLES=ON
cmake --build build --target assetkit_samples

See samples/README.md for individual programs and standalone sample builds.

License

Apache 2.0.

Contributors

This project exists thanks to all the people who contribute.

Backers

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Trademarks

glTF and COLLADA and their logos are trademarks of Khronos Group.